Biochemical Engineering Flashcards by . .

A competitive inhibitor of an enzyme is usually

structurally similar to the substrate.

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Linear inhibition is sometimes called as

complete inhibition

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The types of inhibition pattern based on Michaelis Menten equation are
a. competitive
b. non-competitive
c. uncompetitive
d. all of the above

d. all of the above

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The effect of non-competitive inhibition on a Lineweaver-Burk Plot is that

it can change the y-intercept

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The rate-determining step of Michaelis Menten kinetics is

the complex dissociation step to produce product

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In competitive inhibition a factor is obtained from the measurement of

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Which of these proteases is not a cysteine active site protease?
a. Calpain
b. Cathepsin D
c. Papain
d. None of the above

b. Cathepsin D

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Given an enzyme with a Km = 10m M and Vmax = 100 m mol/min. If [S] = 100 m M, which of the following will be true?
a. A 10-fold increase in Vmax would increase velocity 10-fold y
b. A 10-fold decrease in Km would increase velocity
c. Both (a) and (b)
d. A 10-fold increase in Vmax would decrease velocity 20-fold

A 10-fold increase in Vmax would increase velocity 10-fold y

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The conformational change in an enzyme after the substrate is bound that allows the chemical reaction to proceed, can be explained by

induced fit

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The active site of an enzyme remains
a. at the center of globular proteins
b. rigid and does not change shape
c. complementary to the rest of the molecule
d. none of the above

d. none of the above

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Which category of enzymes belongs to class two in the international classification?
a. Hydrolases
b. Ligases
c. Transferases
d. Isomerase

Transferases

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The Woolf-Augusteinsson-Hofstee plot of ν versus ν/[S] and the Eadie-Scatchard plot of ν/[S] versus ν do not involve reciprocals of ν therefore are considered to be more reliable when the error in v is

significant

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The relationship between Keq, Km and Vmax is known as

Haldane equation

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The reciprocal equation for non-competitive inhibition can be arranged to the equation for the

Dixon plot

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Which of the following statements is true for enzymatically catalyzed reaction?

The activation energy of the reaction is lowered so that a larger proportion of the substrate qualifies to overcome it

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Which of the following common drugs is not a specific enzyme inhibitor?

Iodine

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In a Lineweaver-Burk Plot, competitive inhibitor shows which of the following effect?

It changes the x-intercept

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Which of the following statements is not true?
a. Enzymes are proteins that bind to specific substrates and increase the velocity of reactions involving those substrates
b. Enzymes function by overcoming the activation energy barrier of a reaction
c. Enzymes make thermodynamically favorable reactions to proceed; they cannot make unfavorable reactions to occur
d. Enzymes only function when they are in intact cells

d. Enzymes only function when they are in intact cells

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An enzyme and a reactant molecule maintain relationship as

a temporary association

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An enzyme is assayed at an initial substrate concentration of 2 x 10-5M. In 6-minute, half of the substrate is used. The Km for the substrate is 2 x 10-3M. The value of k in minute is

0.115

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The plot commonly used for determining the value of Vmax is
a. Lineweaver Burk plot
b. Langmuir plot
c. Eadie Hofstee plot
d. all of these

d. all of these

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Quasi steady state is also known as

Pseudo steady state

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Which of these enzymes contains a Zinc (Zn) ion?
a. Carboxypeptidase A
b. Phosphorylase B kinase
c. Tyrosine hydroxylase
d. Phosphodiesterase

Carboxypeptidase A

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A noncompetitive inhibitor of an enzymecatalyzed reaction

increases KM and reduces Vmax

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An allosteric inhibitor of an enzyme usually

participates in feedback regulation

A classical uncompetitive inhibitor is a compound that binds

reversibly to the enzyme substrate complex yielding an inactive ESI complex

Which graphical method is used to determine an enzyme degree of cooperativity?

Hill plot

The ratio of the amount of a protein present in a sample, which is used as a measure of purification, is known as

specific activity

If a reaction occurs in the absence of inhibitor with rate ν0 and in the presence of inhibitor with rate νi, the degree of inhibition is defined as

(ν0 - νi)/ν0

The rate equation in competitive inhibition based on Michaelis Menten equation is given by

rmaxS/(Km(1+I/Ki) +S))

Classical noncompetitive inhibition is obtained only under

rapid equilibrium conditions

In the steady state the material balance equation for any component of a system is

rate of addition - rate of removal + rate of formation = 0

For an enzyme that displays Michaelis-Menten kinetics, the reaction velocity (as a fraction of Vmax) observed at [S] = 2 KM will be

0.66

Predominantly uncompetitive inhibition may be called when

competitive inhibition is greater than uncompetitive inhibition

An enzyme has a Km of 4.7 x 10-5M. If the Vmax of the preparation is 22m moles liter-1 min-1, what velocity would be observed in the presence of 2.0 x 10-4M substrate and 5.0 x 105M of a competitive inhibitor?

13.54μ moles liter-1min-1

The rate equation in non-competitive inhibition based on Michaelis Menten equation is given by

rmaxS/ (Km + S) (1+I/Ki)

Which of the following statement(s) regarding enzymes, is/are false? a. Enzymes are always proteins that function as catalysts b. Enzymes provide activation energy for reactions c. Enzyme activity can be regulated d. Enzymes may be used many times for a specific reaction

b. Enzymes provide activation energy for reactions

The slope of Lineweaver Burk plot for Michaelis Menten equation is

Km/Vmax

The initial velocity, V0, of an enzyme catalyzed reaction reaches Vmax as

1/[S] → 0

The usual method(s) to solve rate equation of simple enzyme kinetics is/are a. Michaelis Menten approach b. Briggs-Haldane approach c. Numerical solution approach d. all of these

d. all of these

Michaelis Menten equation can also be written as a. (-Cs)/r = (Cs/rmax)+(Km/rmax) b. 1/r = (1/rmax)+(Km/(rmax.Cs)) c. r = rmax-(Km.r/Cs) d. All of these

d. All of these

Which of the following step is assumed to be the slowest step in the Michaelis Menten equation?

The product releasing step

When substrate [S] = KM (Michaelis-Menten constant), the velocity of an enzyme catalyzed reaction is about

0.5 * Vmax

A classical noncompetitive inhibitor has

no effect on substrate binding and vice versa

The active site of an enzyme differs from an antibody-antigen binding site in that the enzyme active site

catalyzes a chemical reaction

The active site of an enzyme differs from an antibody-antigen binding site in that the enzyme active site

catalyzes a chemical reaction

Enzymes are basically

Proteins

Which of the following refers to pseudo steady state?

d(CES)/dt = 0

Which of the following refers to pseudo steady state?

d(CES)/dt = 0

Most enzymes work by

decreasing energy of activation

Which category of enzymes belongs to class 5 in the international classification?

Isomerases

Lock and key theory is based on the compatibility of

enzyme and substrate

When an enzyme is functioning at Vmax, the rate of the reaction is limited by

the rate at which the enzyme can convert substrate to product

When an enzyme is functioning at Vmax, the rate of the reaction is limited by

the rate at which the enzyme can convert substrate to product

When an enzyme is functioning at Vmax, the rate of the reaction is limited by

the rate at which the enzyme can convert substrate to product

The equation for the rate of product formation for simple enzyme reaction is given by (Where rmax, maximum reaction rate, Cs substrate concentration, Cp product concentration ES, CES enzyme-substrate concentration)

rp = rmax Cs/(Km+Cs)

When [S] = 0.1 *KM, the velocity of an enzyme catalyzed reaction is about:

0.1 * Vmax

Juice clarification extraction is facilitated by using

Cellulases

Lysozyme is naturally present in a. egg white b. bacteria c. tears & milk d. all of these

d. all of these

Enzymes act as antimicrobials a. by depriving an organism of a necessary metabolite b. by generating a substances toxic to the organism c. by attracting a cell wall component d. all of the above

d. all of the above

Trichoderma β-glucanase is reported

to stabilize mashing

The bitter taste of the high protein materials is reduced by using

Protease

Sulphydryl oxidase is used for

UHT milk off flavor removal

α-amylase is an endo enzyme which requires

Liquefaction of starch to dextrin is carried out by

α-amylase

Milk digestibility is improved by using

Lactase

Which of the following mainly serve to convert starch into high fructose corn syrup (HFCS)? a. α-amylase b. Gluco-isomerase c. Gluco-amylase d. all of these

d. all of these

Lysozyme

catalyses hydrolysis of β-1-4 linkages between N-acetyl muranic acid and Nacetyl glucosamine in peptideoglycan

Hersperidinase is used for

juice clarification

Which of the following metallic ion is there in ascorbic acid oxidase?

Which of the enzyme combination is commercially used for the removal of oxygen? a. Glucose oxidase-cellulase b. Glucose oxidase-catalase c. Glucose oxidase-lactase d. All of these

Glucose oxidase-catalase

Citrus juice debittering can be carried out using

Limoninase

Which of the following enzyme is responsible for causing vitamin B deficiency disease beriberi? a. Ascorbic acid oxidase b. Thiaminase c. Lipoxygenase d. None of these

b. Thiaminase

Soya off flavour removal may be achieved using

aldehyde oxidase

The reduction in off flavour of beer is practiced through

diacetyl reductase

Discoloration can be achieved by using

anthocyanase

The prosthetic group present in phenolase enzyme is

Enzymes degrade, alter or synthesize a food component through a. oxidation/reduction/isomerization b. hydrolysis/synthesis c. group transfer d. all of the above

d. all of the above

The enzyme β-galactosidase is also known as

isomerase

Chymosin hydrolyses the bond between

Phenyl alanine and methionine

The function of the disengagement zone in an airlift fermenter is to a. prevent CO2 rich bubbles from entering the downcomer b. reduce the velocity of the bubbles c. reduce liquid loss as aerosols d. all of the above

d. all of the above

Stationary phase is described as

no further increase in the cell population after a maximum value

In the accelerated phase, cell starts to

increase and the division rate increases to reach a maximum

The Monod model predicts that the specific growth rate

will increase with the concentration of the growth limiting substrate until it reaches a maximum value

A mixed fermentation is one, which produces

both acid and alcohol

The phenomenon in which substrates are used in a sequential manner is known as

diauxie

The dilution rate, D is defined as (where F = volumetric flow rate, VR = total volume of culture in the reactor and μ specific growth rate)

F/VR

Diauxie is

the stagewise uptake of nutrients

An open system in which the growth rate is maintained by adding a nutrient (present in limiting quantities) at the same rate as that medium containing micro-organism is removed is called

Chemostat

In the death phase

nutrients available for the cells are depleted and begin to die

The maximum specific growth rate of an organism depends on a. medium composition b. temperature c. pH d. All of these

d. All of these

Which of the following is not correct for the Monod model and the Michaelis Menten Model a. The Michaelis Menten Model was derived from a curve fitting exercise b. The Michaelis Menten model was derived from an analysis of the mechanism of microbial growth c. The Monod model was derived from an analysis of the mechanism of microbial growth d. All of the above

c. The Monod model was derived from an analysis of the mechanism of microbial growth

Bubble column reactor has

large height to diameter ratio

An open system in which the growth rate is maintained by the removal and addition of media at such a rate as to maintain a constant cell density is called a

Turbidostat

Wash out in steady state fermentation occurs when

dilution rate is higher than the maximum specific growth rate

Fermenter should be filled with medium upto

75-80%

Bacterial growth curve is obtained by plotting

log of number of cells versus time

When intracellular enzymes of whole cells are to be used in a bio-conversion process, it is often necessary to____________the cells.

Permeabilize

Heat transfer rates (per unit volume) will be lowest in

Continuous packed bed reactor

The function(s) of the draft tube in an airlift bioreactor is a. to reduce bubble coalescence b. to improve circulation c. to even out shear conditions throughout the reactor d. all of the above

d. all of the above

The Monod Model relates

specific growth rate to the substrate availability

The height to diameter ratio (H/D) for the column fermenters is

The high oxygen transfer efficiencies of airlift bioreactors is due to a. the large aspect ratio of the reactor, which leads to a high gas hold-up b. the large aspect ratio of the reactor, which leads to a high oxygen solubility at the base of the reactor c. the draft tube, which reduces bubble coalescence in the reactor d. all of the above

d. all of the above

The maximum specific growth rate (μm) of an organism in batch culture is equal to slope of a plot of

In [biomass] against time for exponential phase data only

The region of an airlift bioreactor in which the liquid travels in a downward direction is called the

Downcomer

Population doubling time, td can be expressed as (where μ is the specific growth rate.)

ln2/μ

A higher Ks value of Monod's equation means

greater affinities to substrate

The increased air flow rate in bubble column fermenter can cause excessive foaming and high retention of air bubbles in the column which

decreases the productivity of the fermenter

In an airlift bioreactor, the spent gases released from the liquid are called

disengagement zone

The contents in jet loop reactor are mixed through

external pumping

The specific growth rate (μ) is defined as

the rate of individual cells division or increase in their biomass

The number of baffles in a standard stirred tank bioreactor is

In the stationary phase

growth rate is equal to death rate

Which of the following is an example of a mathematical model? a. Volume of cuboid = length x breadth x height b. The Monod Model c. The Michaelis Menten Equation d. All of the above

d. All of the above

Biomass concentrations during fermentation is a. diluting the samples to optical density less than 0.3 b. monitored by controlling the changes in biomass concentrations c. considering that optical density is proportional to the surface area of the biomass in the sample d. all of the above

d. all of the above

Chemostats work on the principle of

maintaining uniform nutrients concentration

During the exponential phase the maximum specific growth rate equals specific growth rate as

concentration of growth limiting substrate is much greater than the Monod constant

An internal draft tube is preferred to an external draft tube because

it is easier to clean and sterilize a reactor

A functional relationship between the specific growth rate and essential compounds concentration was proposed by Monod in

1942

The optical density sometimes drops during the lag phase because

cells tend to grow without dividing leading to a decrease in the surface area to volume ratio

The application of just in time (JIT) manufacturing techniques in biotechnology is important because a. raw materials used in biotechnology are biodegradable b. the products of biotechnology are biodegradable c. it is a very competitive business d. all of the above

d. all of the above

Residence time distribution (RTD) of a reactor is independent of

micro mixing

The bubble column fermenter is usually limited to

aerobic fermentations

A culture in a closed vessel to which no additional medium is added and from which no waste products are removed is called a __________ culture.

Batch

If the specific growth rate, μ. is constant with time during the exponential growth period, the equation correlating bacterial number density Cn), cell number concentration with respect to time can be expressed as

Cn= Cn0 exp [μ (t - t0)]

The diameter of the baffles in a standard stirred tank bioreactor ranges from

1/10th - 1/12th of the tank diameter

During the log phase cell numbers increase exponentially

because cells are auto catalysts

Lag phase occurs mainly due to

substrate disliking

In a batch reactor specific growth rate

changes during the fermentation

Turbidostat is recommended when continuous fermentation needs to be carried out at

high dilution rates near the washout point

The specific growth rate is affected by a. substrate concentration b. product concentration c. oxygen supply d. all of these

d. all of these

The main function(s) of a draft tube in an air lift fermenter is/are to

distribute shear forces throughout the reactor and minimize bubble coalescence

Which of the following is incorrect? a. The mechanical agitation and aeration are effective for suspension of cells b. The mechanical agitation and aeration are effective for mixing the medium c. STF can't be used for high viscosity medium d. The mechanical agitation and aeration are effective for oxygenation

c. STF can't be used for high viscosity medium

The contents in bubble column and air lift reactor are mixed through

compressed air

Which of the following statements would be appropriate while comparing bubble column and air lift fermenter of the same size? a. The average bubble size is smaller in an airlift bioreactor b. Oxygen transfer rate is higher in an airlift bioreactor c. The surface area for gas exchange is higher in an airlift bioreactor d. All of the above

d. All of the above

During the lag phase

cells synthesize new proteins and membrane components

Concentration of the growth limiting substrate means

the concentration of the substrate that controls the growth rate of the cells

Tower fermenters are used for

continuous beer production

In wastewater treatment, which bioreactor is generally used?

Trickle bed reactor

The contents in stirred tank rector are mixed through

a mechanical agitator

The height to diameter ratio (H/D) for the tank fermenters is

The relatively large volume (10 to 40% of total fermenter volume) of the seed culture is employed to

decrease the overall fermentation time

In an airlift bioreactor, the air sparging region is called

air riser

The air riser is located on the outside of the draft tube for the large-scale airlift bioreactors because of

better heat transfer efficiencies

At the end of the lag phase, when growth begins, the division rate increases gradually and reaches a maximum value in the exponential growth period. This transitional period is commonly called the accelerated growth phase and is often included as a part of the

lag phase

Which of the following(s) is/are considered the limitations of the exponential growth model?

It does not consider factors that causes cells growth to stop or slow

To describe components of an airlift bioreactor which of the follow-ings are generally included?

Disengagement zone, air riser, downcomer

The viscosity of liquid was classified as both dilatant and rheopectic, which means that the viscosity

increased with stirring speed and increased with mixing time

A fluid in which the viscosity decreases with increasing stirrer speed and mixing time, can be represented as

pseudoplastic, thixotropic fluid

Filamentous fungal cells are more shear sensitive than bacterial cells because of a. the presence of citin in cell walls of filamentous fungi b. larger in size than bacterial cells and therefore are more susceptible to shear forces c. fungal cells are much larger than bacterial cells d. all of the above

d. all of the above

The viscosity of water at STP is approximately

0.001 kg.m-1.s-1

Bubble free aeration systems requires

silicone tubing or gas permeable membranes to facilitate gas transfer

Non-linear relationship between shear stress and shear rate exists in

non-Newtonian fluids

If the viscosity of a fluid decreases with increasing stirrer speed, then the nature of the fluid is

Pseudoplastic

A pseudoplastic fluid is one in which the viscosity

decreases with increasing stirrer speed

A viscoelastic fluid is one in which the viscosity

changes during mixing but returns to its original state after mixing

Mixing in stirred tank reactors can

be described as either laminar, transient or turbulent

In animal cell bioreactor, bubble damage can be minimized by a. the addition of a shear protectorant b. using a bubble free oxygen delivery system c. headspace aeration d. all of the above

d. all of the above

The viscosity of a fluid changes with either stirrer speed or mixing time. But when mixing ceases, the viscosity returns to its original state. This fluid is best described as

Viscoelastic

In sparged mammalian cell bioreactors, the cell damage is caused because of

shear stress arising during mixing of the cell culture fluid

The SI unit for viscosity is

kg.m-1. s-1

The viscous nature of a non-Newtonian fluid

changes with the level of power input and/or the length of time during which the fluid is mixed

Which of the following compound, if added to a solution will lead to the greatest increase in viscosity?

A long chain protein such as albumin

A Brookfield viscometer measures viscosity by determining

the torque required to move an impeller at a set speed

Which of the following factors will affect the sensitivity of animal cells to shear conditions? a. Cell size b. Availability of nutrients in the medium c. The presence of shear protectorants in the medium d. All of the above

d. All of the above

The best described action of Pluronic F68 (nonionic detergent) in a cell culture medium is that, it

acts on the surface properties of the cells and the culture medium

Water is a a. Newtonian fluid b. Pseudoplastic c. Dilatant d. Rheopectic

a. Newtonian fluid

Which of the following affect the Kolmogorov eddy size? a. Stirrer speed b. Physical properties of the liquid c. Size and type of impeller d. All of these

d. All of these

A liquid is flowing at 11,400 l.h-1 along a pipeline having a diameter of 4 cm. If the liquid has a density of 1 g.ml-1 and viscosity of 0.001kg.m-1.s-1, then the liquid would be in the

turbulent phase

The viscosity of a fluid increases with the length of time that it is being mixed. This fluid would be best described as being

Rheopectic

Which of the following can act as a shear protectorant? a. Serum b. Silicone oil c. Glucose d. Glutamic acid

a. Serum

The viscosity of a fluid increases with increasing stirrer speed. This fluid would be best described as being

Dilatant

A dilatant fluid is one in which the viscosity

increases with increasing stirrer speed

A rheopectic fluid is one in which the viscosity

increases with mixing time

A fluid in which the viscosity increases with increasing stirrer speed and mixing time can be called as

dilatant, rheopectic fluid

The medium will have the highest viscosity (considering that the cells do not secrete gums) with the presence of

filamentous fungi that grow as long poorly branched chains

A Newtonian fluid is one in which the viscosity

is constant regardless of the stirrer speed or mixing time

Which pattern of mixing is preferred in stirred tank reactors during the culture of aerobic microorganisms? a. Laminar flow b. Transient flow c. turbulent flow d. all of these

c. turbulent flow

Animal cell cultures do not have much effect on shear forces because

the cell size is generally smaller than the critical eddy size at which shear will have an effect

The viscosity of the culture fluid is classified as both pseudoplastic and thixotropic which indicates that the viscosity

decreases with stirring speed and decreases with mixing time

Pluronic F68 is added to cell culture media as

a shear protectorant

A stirred tank reactor containing a fluid with a density of 2.5 g.ml-1 and viscosity of 0.002 kg m-1s-1 is mixed at 120 rpm. If the fluid is mixed with an impeller having diameter 50 cm, then the Reynolds number of the liquid in the reactor is

12,50,000

If the viscosity of a fluid decreases with the length of time that it is being mixed, then this fluid is

Thixotropic

Which of the following describes the importance of the Kolmogorov eddy size in the biotechnology? a. The Kolmogorov eddy size is a measure of the smallest eddy size in a liquid b. When the Kolmogorov eddy size become equivalent or smaller than the cell or particle diameter, then the cell or particle will become susceptible to shear damage c. At the Kolmogorov eddy size, much of the energy of the originating eddy will be released d. All of the above

d. All of the above

A thixotropic fluid is one in which the viscosity

decreases with mixing time

Newtonian fluid is one in which the viscosity

remains constant with time and power input

Reynolds number for laminar flow over a plate should be less than

5 x 10^5

The approach which is commonly used to determine the level of damage to animal cells in a culture medium is to monitor

the level of lactate dehydrogenase activity

A Brookfield viscometer cannot determine the shear stress because a. the shear stress is not defined b. a computer is required c. the impeller type is given only by numbers d. all of the above

a. the shear stress is not defined

Which of the following is correct? a. The viscosity of liquids and gases decrease with increasing temperature b. The viscosity of liquids and gases increase with increasing temperature c. the viscosity of gases increases with increasing temperature, but decreases in liquids d. the viscosity of gases decreases with increasing temperature, but decreases in liquids.

c. the viscosity of gases increases with increasing temperature, but decreases in liquids

The Komologorov eddy size a. is constant at all stirrer speeds b. increases with stirrer speed c. decreases with stirrer speed d. becomes zero when the stirrer speed is very low

c. decreases with stirrer speed

Pluronic F68 protects mammalian cells from damage stems as it is a/an

surface active agent which stabilizes foams

Reynolds number for turbulent flow over a plate should be more than

10^6

Concentration polarization can be reduced further by a. pre filtering the solution b. reducing the flow rate per unit membrane surface area c. back washing periodically d. all of the above

d. all of the above

A system which requires less solvent and produces a more concentrated extract phase, is desired with a

a. large distribution coefficients

The efficiency of cell disruption in a bead mill depends on the a. concentration of the cells b. amount and size of beads c. type and rotational speed of agitation d. all of these

d. all of these

A common filter medium is the cloth filter generally made of a. Canvas b. synthetic fabrics c. metal or glass fiber d. all of these

d. all of these

An ion exchange resin is composed of a. polymeric network b. ionic functional groups c. counter ions d. all of these

d. all of these

Maintenance cost varies from

4-8% of the capital cost

The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between

30-60% by volume

Assuming the laminar flow across the filter, the rate of filtration (dVf/dt) can be expressed as a function of pressure drop Dp by the modified D'Arcy's equation as (where A is the area of filtering surface, K is the D'Arcy's filter cake permeability and Lis the thickness of the filter cake)

(1/A) dVf/dt = Δp/μ(L/K)

Filtration leaf test results indicate that the filtration rate of a protein product is 100 dry lbs/(ft2 hr). What size production filter would be required to obtain 100 dry lbs of filter cake/hr?

1.54 ft2

Selectivity can be expressed as

ratio of the distribution coefficients in different solute

The disk centrifuge is the type of centrifuge used most often for bio separations due to its

lesser cost

The stage wise operation of adsorption is called

contact filtration

Which of the following is not the physical method for the cells rupturing? a. Milling b. Homogenization c. Ultrasonication d. Enzymatic digestion

d. Enzymatic digestion

Conventional adsorption is a a. reversible process b. irreversible process c. either reversible or irreversible d. none of these

a. reversible process

If the solute passes through membrane freely, the the rejection coefficient (s) is

If the membrane rejects all solute, the rejection coefficient (s) is

In antibiotic manufacturing processes, the fermentation time ranges from

4-5 weeks

The conventional filtration involves the separation of large particles generally

dp>10μm

Which of the operation does not come under upstream processing? a. Media preparation b. Inoculum development c. Effluent treatment d. Storage of raw material

c. Effluent treatment

For cost analysis in a fermenter system, the depreciation cost varies from

6-10% of the capital cost

Micro filtration refers to the separation of suspended material such as bacteria by using a membrane with spore sizes of

0.02 to 10μm

Start up expenses in a fermentation industry varies from

5-10% of the capital cost

The solvent flux across the membrane can be expressed as (where A is the area, Lp is the membrane permeability, σ is the reflection point, Δp is applied pressure and Δπ is the osmotic pressure)

J = Lp(Δp - σΔπ)

Which of the following is considered as a pretreatment to the biological feeds? a. Heating to denature the proteins b. Addition of filter aids to increase the porosity c. Addition of electrolytes d. All of the above

d. All of the above

For the extractions operation, the selectivity should be

> 1

The purity of a solute collected between two times t1 and t2 during chromatographic separation can be calculated as

amount of solute eluted / amount of impurity eluted

Chromatography is based on the

different rate of movement of the solute in the column

The correlation often employed to correlate adsorption data for protein is (where Ymax is the maximum amount of solute adsorbed per mass of adsorbent, X is the mass fraction of solute in the diluent phase in solute-free basis, KL is a constant and Y is the equilibrium value of the mass of solute adsorbed per mass of adsorbent)

Y = YmaxX/(KL+X)

A typical tubular centrifuge has a bowl of 2 to 5 inch in diameter and 9 to 30 inch in height with a maximum rotating speed of

15,000 to 50,000 rpm

Water insoluble enzymes can be prepared by using multifunctional agents bifunctional in nature and have

Low molecular weight

Functional groups of the nonessential amino acids that are suitable for the immobilization process are a. Free α-, β- or γ carboxyl groups b. α or β amino groups c. phenyl, hydroxyl, sulfhydryl, or imidazole groups d. all of the above

d. all of the above

Which medium is used for the production of Penicillin using immobilized cells?

Glucose medium

Which of the following is taken as an assumption in the distributed model? a. The reaction occurs at every position and the kinetics of the reaction are of the same form as observed for free enzyme. b. Mass transfer through the immobilized enzyme occurs via molecular diffusion. c. There is no mass transfer limitation at the outside surface of the spherical immobilized enzyme. d. All of the above

All of the above

The immobilized enzyme produced by micro encapsulation technique provides

An extremely large surface area

Which of the following is considered as a disadvantage to the adsorption method of immobilization? a. It is possible to separate and purify the enzymes while being immobilized. b. The enzymes are not usually deactivated by adsorption. c. The adsorption is a reversible process. d. State of immobilization is very sensitive to solution pH, ionic strength, and temperature.

State of immobilization is very sensitive to solution pH, ionic strength, and temperature.

During the enzymatic reaction of an immobilized enzyme, the rate of substrate transfer is

Equal to that of substrate consumption

The immobilized technique involving chemical method is

Covalent bond formation dependent

For a steady state condition, the change of substrate concentration (dCS/dt) is

Zero

Damkohler number (NDa) is

The ratio of the maximum reaction rate to the maximum mass transfer rate.

For glucose isomerization by immobilized enzyme, the reactor generally used is

Packed Bed

If Damkohler number, NDa >>1, the reaction rate is much greater than the mass transfer rate and the overall reaction is controlled by the rate of mass transfer. In this case, the enzyme reaction can be described as (where Csb and Cs are the substrate concentration in bulk of solution and at the immobilized enzyme surface respectively. ks mass transfer coefficient, and a is the surface area of an immobilized enzyme particles)

rp = ksaCsb

The most commonly employed cross-linked polymer is the

Polyacrylamide gel

Which of the following is not the correct answer? a. Immobilized enzyme may show selectively altered chemical properties. b. Immobilized enzyme may show selectively altered physical properties. c. Immobilized enzyme may simulate the realistic natural environment where the enzyme come from the cell. d. None of the above

d. None of the above

Commonly employed water insoluble supports the covalent attachment of enzyme include a. Acrylamide based polymers b. Polypeptides c. Dextran d. All of these

d. All of these

Which of the following is not a physical method of immobilization? a. Adsorption b. Entrapment c. Micro encapsulation d. None of these

d. None of these

The support material for immobilization of cells of Bacillus subtilis is

Agarose and carbodiimide

The intraparticle mass transfer resistance can affect the rate of enzyme reaction, if enzymes are immobilized by a. Copolymerization or microencapsulation b. Cross linking using multifunctional reagents c. Adsorption d. All of the above

a. Copolymerization or microencapsulation

The covalent attachment of enzyme molecules is via a. Nonessential amino acids residues to water insoluble, functional supports b. Essential amino acids residues to water insoluble, functional supports c. Nonessential amino acids residues to water soluble, functional supports d. Essential amino acids residues to water soluble, functional supports.

a. Nonessential amino acids residues to water insoluble, functional supports

To measure the extent to which the reaction rate is lowered because of resistance to mass transfer, the effectiveness factor of an immobilized enzyme, η can be defined as

Actual reaction rate/rate if not slowed by diffusion

Which is not the method for producing immobilized enzymes with multifunctional reagents? a. Enzymes are adsorbed on the surface active support followed by intermolecular cross linking. b. Functional groups are introduced on the support to react covalently with enzymes. c. Enzymes are cross linked intermolecularly. d. None of the above

d. None of the above

The immobilization technique involving physical method is

Non-covalent bond formation dependent

Which of the following is the commonly employed adsorbents? a. Calcium carbonate b. Alumina c. Celluloses d. All of these

d. All of these

Various techniques are available for determining the effective diffusivity of solute in gel. Thin disk method uses

A diffusion cell with two compartments divided by a thin gel.

The effectiveness factor increases with the

Increase of diffusivity and decreased with the increase of particle size.

Yield coefficient represents

Conversion efficiency of a substrate into product.

The lowest biomass yield in a culture of Escherichia coli will be in

An aerated batch culture containing an initial high concentration of glucose.

When two populations compete for a single growth limiting substrate in a continuous fermenter, which organism would not be washed out? a. Organism maintaining the highest substrate concentration. b. Organism maintaining the lowest substrate concentration. c. Both (a) and (b) d. Organism maintaining the moderate substrate concentration.

b. Organism maintaining the lowest substrate concentration.

The continuous cultures are not widely used in industry because a. They are not suited for the production of secondary metabolites. b. Contamination or mutation can have a disastrous effect on the operation. c. The government will not approve the licensing of pharmaceuticals produced in continuous cultures. d. All of the above.

d. All of the above.

The lowest yield of ATP is in

Fermentation

Mixing in an anaerobic sludge blanket reactor is due to

Release of gases by the microbial populations.

In batch culture, protogon is produced from peptone during the stationary phase with a yield of 0.4 protogon mg per g of peptone. If it is to be produced in a chemostat at a dilution rate of 0.5 h-1 from a medium containing 10 g/L of peptone, then the rate of protogon synthesis would be

0 g/L-h

Formation of end product by Lactococcus lactis will become non-growth associated as lactic acid accumulates because a. Cells will redirect ATP to anabolism. b. Cells will redirect NAD+ to anabolism. c. Cells will redirect ATP to facilitate the diffusion of lactic acid and H+ out of the cells. d. Cells will redirect ATP to the active transport of lactic acid and H+ out of the cells.

Cells will redirect ATP to the active transport of lactic acid and H+ out of the cells.

Which of the following would not be subjected to the “glucose effect”? a. Aspergillus fumigatus b. Saccharomyces cerevisiae c. Escherichia coli d. Aspergillus niger

c. Escherichia coli

Immobilized cell reactors for wastewater treatment have the advantage of having/being a. Higher cell concentration b. More stable and prevent washout c. Higher dilution rate before the cells washout d. All of the above

d. All of the above

Which of the statement is true for continuous reactor at steady state? a. The rates of biomass, substrate, and product concentrations are zero. b. Biomass, substrate, concentrations are zero. and product c. Biomass, substrate, and product concentrations do not change with time. d. Biomass, substrate, and concentrations change with time.

c. Biomass, substrate, and product concentrations do not change with time.

A continuous bioreactor in which only the flow rate is used to control the rate of cell or product productivity is called

Chemostat

For organisms growing in a chemostat, the specific growth rate

Can be determined from the dilution rate.

Saccharomyces cerevisiae is being grown in a chemostat converts glucose to biomass, ethanol, glycerol, and carbon dioxide. At steady state, the concentration of glucose, biomass, ethanol, and glycerol will

Be constant.

In aerobic yeast fermentation for production of citric acid from alkanes using a fed-batch culture, why alkanes are slowly fed to the yeast?

Fast addition of alkanes will inhibit the cells and reduce oxygen transfer rates.

A continuous reactor has a dilution rate of 0.5/h. Its residence time would be

2 h

Which of the following is used to calculate mass of substrate in the reactor? a. Flow rate x substrate concentration in the reactor b. Volume of reactor x substrate concentration in reactor c. Flow rate x mass of reactor d. Volume of reactor x flow rate

b. Volume of reactor x substrate concentration in reactor

If biomass yields are constant, then the biomass productivity of a culture growth in continuous reactor will

Increase with dilution rate until washout

Low dissolved oxygen concentrations leads to

Low biomass yields

Low dissolved oxygen concentrations leads to

Low biomass yields

A fed-batch reactor containing 1 g/L of substrate in 2 liter of medium. It is fed with 1 g/L of substrate at the rate of 1 liter per hour. After 10 hours, the concentration of substrate in the reactor was 0.5 g/L. the mass of substrate that was used by the culture in the reactor was

Toxins accumulated in a reactor can lead to low biomass yields probably due to which of the following? a. NAD+ is diverted away from homeostasis to anabolism. b. ATP is diverted away from homeostasis to anabolism. c. NAD+ is diverted away from anabolism to homeostasis. d. ATP is diverted away from anabolism to homeostasis.

d. ATP is diverted away from anabolism to homeostasis.

The cellular productivity in a continuous stirred tank fermenter (CSTF) increases with an increase in the dilution rate and reaches a maximum value. If the dilution rate is increased beyond the maximum point, the productivity will

Decrease abruptly.

Fluidized bed bioreactors provide higher mass transfer rates than packed bed bioreactors because a. Mixing is higher in fluidized bed bioreactors. b. Particles move with the fluid in a fluidized bed bioreactor. c. Immobilized particles are smaller in the fluidized bed bioreactors. d. All of the above.

b. Particles move with the fluid in a fluidized bed bioreactor.

In fed-batch fermentation, mass of substrate utilized is calculated using the relationship

Initial mass of substrate in the reactor – final mass of substrate in the reactor + flow rate x [substrate in the feed]

A chemostat has a liquid volume of 2 liters and is being fed at a rate of 4 liters per hour. Dilution rate for this reactor will be

2 h-1

Mixing per unit volume is observed to be poorest in

Continuous packed bed reactor

The growth of an organism on glucose is described by the following Monod model parameters: μm = 0.5 ℎ−1 and Ks = 0.1 g/L−1, if the concentration of glucose in the feed is 10 g/L and the dilution rate is set to 0.4/h, then the steady state concentration of glucose in the effluent will be

0.5 g/L

A continuous reactor at steady state contains 0.04 g/L of biomass and 0.02 g/L of phenol. The feed contained 0.1 g/L of phenol. The biomass yield would be

0.5 g/g

A culture system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called ___ culture system

Continuous

The main reason for production of antibiotics in fed batch reactors is a. The presence of precursors is often toxic to the cells. b. Higher yields when cells enter the stationary phase. c. Higher yields when cell growth slows. d. All of the above.

d. All of the above.

Fed batch reactors is used to produce vinegar because a. It can maintain low ethanol concentrations. b. It can maintain low acetic acid concentrations. c. Acetic acid bacteria tend to ferment at high ethanol concentrations. d. All of the above

a. It can maintain low ethanol concentrations.

When a culture of fermenting yeast becomes metabolically uncoupled, ethanol

Production becomes non-growth associated.

Mixing profiles closest to plug flow are observed in a. Continuous packed bed reactor, b. Stirred tank reactor with biomass recycles. c. Continuous fluidized bed bioreactor. d. All of these.

a. Continuous packed bed reactor,

On a glucose medium, the growth of an organism is characterized by the following Monod model and stoichiometric parameters μm=0.3 ℎ−1, Ks = 0.05 g/L and Yxs = 0.3 g/g. When this organism is grown in a 2liter continuous on a medium containing 10 g/L of glucose added at 1 L/h, the steady state concentration of biomass in the reactor will be

0 g/L

Unsteady state mass balance for dynamic model of continuous stirred tank reactor (CSTR) is a. Time rate of total amount in reactor = rate of addition to reactor – rate of removal + rate of formation b. Total amount in reactor = rate of addition to reactor – rate of removal + rate of formation c. Rate of total amount in reactor = rate of addition to reactor – rate of removal + rate of formation d. None of the above

a. Time rate of total amount in reactor = rate of addition to reactor – rate of removal + rate of formation

A fed-batch reactor initially contains 2 liter of medium. If it was fed at 1 liter per hour, then after 10 hours, the volume of the reactor will be

2 liter

A Bacillus sp. Produces an antibiotic only during the stationary phase when grown in a batch culture. If grown in a 5 liter continuous culture, the steady state productivity of the antibiotic

Will be zero.

In a fluidized bed reactor, the function of the disengagement zone is to a. Reduce loss of particles from the reactor. b. Reduce the velocity of the particles near the surface of the reactor. c. Reduce foaming problems. d. All of the above.

d. All of the above.

Saccharomyces cerevisiae produces high biomass yields at low glucose concentrations and high dissolved oxygen concentrations. Which of the following should be followed for maximizing its biomass productivity? a. Batch fermenter with a high initial glucose concentration. b. Continuous fermenter with a low initial glucose concentration. c. Fed batch fermenter. d. All of the above.

c. Fed batch fermenter.

In a glucose-yeast extract medium, Lactococcus lactis has a maximum specific growth rate (µm) of 1.23/h. what would be the specific growth rate of this organism at steady state in a 4-liter reactor being fed at 2 liters per hour?

0.5/h

Which of the following is not correct with regards to continuous cultures? a. The major industrial scale application of continuous cultures is in wastewater treatment. b. Mutation and contamination present a major risk to the operation of continuous cultures for the production of metabolites. c. The continuous cultures are very useful for the production of pharmaceuticals. d. Continuous cultures have an advantage that they do not need to shut down as regularly as batch culture reactor.

c. The continuous cultures are very useful for the production of pharmaceuticals.

In a plug flow reactor, the highest concentration of substrates is exposed to the cells that

Are located near entrance of feed.

In an activated sludge process, the biomass is recycled to a. Increase the efficiency of the process. b. Reduce sludge volumes. c. Increase the concentration of cells. d. All of the above.

d. All of the above.

A strain of Escherichia coli has a maximum specific growth rate of 0.8/h on a glucose based medium. If this organism is being grown in a chemostat with a dilution rate of 1.2/h, then at steady state the concentration of E. coli in the same medium will

Be zero

A fed-batch reactor containing 2 liters of medium and 0.1 g/L of biomass is fed with a medium containing 1 g/L of substrate at 1 liter per hour. If after 10 hours, the concentration of biomass in the reactor was 0.2 g/L, then the biomass produced during the 10-hour period is

2.2 g

Which of the following organisms will continue their metabolism at high concentrations? a. Pseudomonas aeruginosa b. Saccharomyces cerevisiae c. Bacillus subtilis d. Escherichia coli

a. Pseudomonas aeruginosa

Yeast is typically produced in fed batch reactors because a. Yeast cells produce ethanol at low glucose concentrations. b. Yeast cells ferment at low glucose concentrations. c. Year cells respire at low glucose concentrations. d. All of the above.

c. Year cells respire at low glucose concentrations.

Two continuous bioreactors containing the same organisms, fed with the same feed at the same dilution rate were compared. Reactor 1 started with an initial concentration of glucose of 10 g/L, while reactor 2 contained 0.1 g/L of glucose at the start of the process then at steady state

The concentration of glucose in reactor 1 would be equal to reactor 2.

The production of an amylase from starch by Aspergillus niger is often performed in a fedbatch fermenter. This is due to the reason that a. Fed-batch reactor can be used to minimize starch concentrations and prevent a. niger from fermenting. b. Fed-batch reactor can be used to minimize starch concentrations and thus reduce the viscosity of the medium. c. Continuous reactor can be used to minimize starch concentrations and their inhibitory effects. d. All of the above

b. Fed-batch reactor can be used to minimize starch concentrations and thus reduce the viscosity of the medium.

The fastest route of NADH reoxidation is

Fermentation

In fed batch bioreactor modelling, the rate of change in the bioreactor volume is assumed to be equal to

Flow rate

In fed batch bioreactor modelling, the rate of change in the bioreactor volume is assumed to be equal to

Flow rate

Monoclonal antibodies are typically produced in fed batch reactors because a. Hybridoma cells ferment at high maltose concentrations. b. Hybridoma cells yield higher lactate at high glucose concentrations. c. hybridoma cells respire at high glucose concentrations. d. None of the above

b. Hybridoma cells yield higher lactate at high glucose concentrations.

In plug flow tubular reactor, the axial velocity profile on cross-section will be

Constant

Production of organic acids in batch culture is generally growth associated phase followed by non-growth associated production. The probable reason for this is that

Organic acids uncouple catabolism from anabolism.

The concentration of biomass in a continuous stirred tank reactor is 20 g dry weight per liter. What would be the concentration of biomass in the effluent?

Approximately 20 g dry weight per liter.

The ideal tubular-flow fermenter without radial variations is called

Plug flow fermenter

Pseudo-steady state in a continuous reactor refers to a reactor in which

Concentration oscillate around a mean value

The toxicity of organic acids to cells

Enhances as the pH falls

Which of the following is best described as secondary metabolite? a. Acetic acid produced from the oxidation of methanol. b. Ethanol from the fermentation of glucose. c. Penicillin d. Citric acid from the partial oxidation of glucose.

c. Penicillin

A microorganism which is subjected to the Crabtree effect is most likely to

Ferment in the presence of high concentrations of sugar and dissolved oxygen.

When the product formation is approximately equal to the rate of cell growth, the pattern of produce formation is termed as

Growth associated

Which of the following would be correct concerning the concentration of biomass (X), growth limiting substrate (S), and produce (P) in a chemostat when the cells have been washed out? a. X, S, and P will be zero. b. X, S, and P can not be predicted for the above condition. c. X, and P will be zero while S is equal to the substrate concentration in feed. d. None of the above

c. X, and P will be zero while S is equal to the substrate concentration in feed.

Pseudomonas aeruginosa has a maximum specific growth rate of 0.8/h in a medium with glucose as a growth limiting substrate. To prevent washout, the dilution rate must be set to

Less than 0.8/h

Saccharomyces cerevisiae when grown in high glucose concentration medium, the cells activity depends on which of the following? a. High concentration of dissolved oxygen b. Low concentration of dissolved oxygen c. No effect of dissolved oxygen d. High concentration of dissolved oxygen and sodium salts.

c. No effect of dissolved oxygen

Continuous culture has an advantage over to a batch cultures as a. Continuous reactors do not need to be shut down as regularly as batch reactors. b. Most downstream and upstream processes are continuous in nature and thus the operation of continuous bioreactor can be better integrated into the overall manufacturing process. c. Cells can be maintained at a constant physiological state simply by setting the dilution rate. d. All of the above.

d. All of the above.

In a batch-fed mode, substrate will be added

Only at the end of the fermentation process.

When Escherichia coli grown in a well aerated medium, which of the following will occur? a. Fructose di-phosphate accumulation inside the cells leading to cell respiration. b. Fructose di-phosphate accumulation inside the cells leading to fermentation. c. Fructose di-phosphate will accumulate regardless of the medium composition. d. Fructose di-phosphate will accumulate inside the cells leading to anaerobic respiration.

b. Fructose di-phosphate accumulation inside the cells leading to fermentation.

Power number is expressed as

P0/(N^3 Di^5 ρ)

The power consumption in a stirring vessel can be assessed by using a a. Dynamometer b. Strain gauge attached to agitator shaft c. Watt meter attached to agitator motor d. All of these

d. All of these

Surface renewal theory predicts that the mass transfer coefficient is

Directly proportional to the square root of the molecular diffusivity.

The oxygen transfer rate in a bioreactor will increase if

Detergent-like molecules are added.

Which of the following impellers are used for wide range of viscosities? a. Paddles b. Turbines c. Propellers d. None of these

b. Turbines

Which of the following type(s) of stirrer can be used for microbiological processes? a. Mig b. Intermig c. Turbine d. All of these

d. All of these

The range of width for the baffle in the fermenter is ___ times of vessel diameter.

1/10 to 1/12

The average concentration of oxygen in the boundary layers surrounding the bubbles (C0*) in a reactor is normally determined by

Measuring the steady state concentration of oxygen in the bulk liquid prior to inoculation of the reactor.

Why vortexing is undesirable in the agitation of biological systems? a. The collision between the cells, impeller, and air bubbles will lead to cell damage. b. Poor mixing despite the use of high stirrer speeds. c. Mixing will not be in the turbulent region. d. All of the above.

d. All of the above.

The rate limiting step in the movement of oxygen from the gas phase in a bubble to the cell is the movement of oxygen molecules through

Bubble boundary layer

Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (te). The model correlation KL, mass transfer coefficient and DAB, diffusivity can be expressed as

KL = 2 (DAB / π te) ^0.50

The oxygen uptake requirements of a microbial population is characterized by the following parameters: µm = 0.2 h-1, K0 = 0.2 mg O2 L-1, Y0 = 0.5 mg dry weight/mg O2 and C0,crit = 0.8 mg L-1. The required concentration of cells is 1000 mg L-1 and the saturation oxygen concentration of the medium is 5.8 mg L-1. The required KLa must be greater than

64 h-1

Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?

Moving through the bubble boundary layer.

If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the

Square of the impeller diameter

What is the ratio of depth of liquid in vessel to the diameter of tank (H:Dt)?

1:1

Transient flow range of mixing speed is obtained for

10 < Rei < 10^4

A typical ceiling fan would be best described as a(n)

Axial flow impeller

What is the ratio of diameter of impeller to the diameter of tank (Da:Dt)?

1:3

The reason of using a flat disk in a Turbine is a. To create high shear conditions b. To break up bubbles more efficiently than the impeller blades c. To ensure that the bulk of the energy consumption occurs at the blades. d. All of the above

c. To ensure that the bulk of the energy consumption occurs at the blades.

Which of the following is not considered among the three best-known theories of interphase mass transfer? a. Two-film theory b. Penetration theory c. Surface renewal theory d. Calderbank and Moo-Young theory

d. Calderbank and Moo-Young theory

Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system? a. Addition of antifoams b. Increase in temperature c. Increase in stirrer speed d. Both (a) and (b)

c. Increase in stirrer speed

At 25°C, the saturation concentration of oxygen in water is 1.26 mmol/L and the partial pressure of oxygen is 1 atm. The Henry’s law constant will be

0.793 atm-L/mmol

Turbine impeller consists of flat impeller blades with

A vertical pitch welded to a horizontal disk.

An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it

Discourages bubble coalescence.

Henry’s law relates

The partial pressure of oxygen and the saturation concentration of oxygen in the liquid.

Power number is ratio of

Imposed forced to inertial force.

The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dt) using the following equation.

VL = HL x π x Dt^2 /4

The average fractional gas hold up (H) can be given as (where Zf and Zl are the level of aerated and clear liquid respectively)

H = (Zf - Zl)/Zf

Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions? a. Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor. b. Crystals and precipitates are thoroughly broken down, so as to ensure easy separation of the solids from the mother liquor. c. Both (a) and (b) d. Axial flow impellers provide low shear, energy efficient mixing conditions.

a. Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor.

Which of the following will have the highest surface area available for oxygen transfer? a. A shake flask. b. A standing test tube. c. A non-sparged stirred tank reactor agitated at 400 rpm. d. A sparge stirred tank reactor agitated at 400 rpm.

d. A sparge stirred tank reactor agitated at 400 rpm.

A flooded impeller will lead to poor oxygen transfer rates because

a. Bubbles tend to coalesce under the impeller.

A flooded impeller will lead to poor oxygen transfer rates because

a. Bubbles tend to coalesce under the impeller.

Power consumption by agitation is a. A function of physical properties. b. A function of operating conditions. c. A function of vessel and impeller geometry. d. All of the above

d. All of the above

When liquid is pumped through cooling coil in a stirred tank reactor to cool. Which of the following is not correct? a. If the stirrer speed is increased, the rate will be faster. b. Baffles in the tank will increase the rate of cooling. c. Faster cooling rates at a slower rate of pumping. d. Faster cooling rates at a faster rate of pumping.

c. Faster cooling rates at a slower rate of pumping.

When the height of an aerated bioreactor is increased it will increase the oxygen transfer rate by a. Increasing the partial pressure of oxygen at the base of the reactor. b. Decreasing the saturation concentration of oxygen in the reactor. c. Decreasing the gas hold up d. All of the above.

a. Increasing the partial pressure of oxygen at the base of the reactor.

Which of the following is correct for the offcenter impellers? a. Off-center impellers can be used with any size reactor. b. Off-center impellers should only be used with reactors with volumes less than 10 m3. c. The impeller should never be placed in an off-center position. d. Off-center impellers can be used when volume is greater than 10 m3.

b. Off-center impellers should only be used with reactors with volumes less than 10 m3.

The power required by an impeller in a gas sparged system compared to the power required by the impeller operating at same speed in a gas free liquid is usually

Lesser

Which of the following stirrer requires least amount of energy for same yield? a. Mig b. Intermig c. Turbine d. Disc

b. Intermig

A reactor has a total volume of 50,000 liters. If it has a headspace volume of 10,000 liters, then volume of liquid in the reactor will be

40,000 L

Pure oxygen, if used instead of air will increase oxygen transfer rates because

The saturation concentration of oxygen is higher.

For aerated mixing vessels in an aqueous solution, the mass transfer coefficient (kL) corelating power consumption (Pm_ and fermenter volume (V) can be expressed as

kL ∝ (Pm/V)^0.33

Higher temperatures affect oxygen transfer rates by

Increasing KLa but lowering CO*

The Intermig impeller is a. An axial flow impeller which can be used for the culture of aerobic organisms. b. Directed upwards rather than towards the base of the reactor. c. A fork shaped extensions to the impeller facilitate bubble break up. d. All of the above

d. All of the above

Which of the following is not classified as an axial flow impeller? a. A propeller b. A marine impeller c. A Rushton turbine d. A hydrofoil impeller

c. A Rushton turbine

Power number (NP) is also known as

Newton’s number

Flooding is a condition/phenomenon which occur in a bioreactor when a. The air escapes without being distributed by the agitator. b. The fermenter medium spills out the reactor due to foaming. c. The volume of foam is more than the volume of broth. d. None of these.

a. The air escapes without being distributed by the agitator.

A cylindrical reactor has a liquid volume of 100,000 liters. It has an aspect ratio, the ratio of the channel height to width of 1:1. The height of the liquid in the reactor will be approximately:

5.0 m

Detergent like substances produced by microorganisms during a fermentation will lead to a. Decrease the surface tension of the liquid. b. Accumulate at the gas liquid interface. c. Decrease the rate of bubble coalescence. d. All of the above.

d. All of the above.

A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 liters. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:

1.3 m

In the bubble boundary layer, oxygen concentration can be determined by measuring

The steady state oxygen concentration in a mixed aerated reactor before inoculation.

Impeller damage can be minimized by a. Using specially designed axial flow impellers. b. Using radial flow impellers. c. Using Intermig impellers. d. All of the above.

a. Using specially designed axial flow impellers.

To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed? a. Liquid volume in the flask is reduced. b. Stirrer speed is increased. c. Baffled flasks are used. d. All of the above

d. All of the above

In the design of a paddle agitator, the ratio of paddle diameter to tank diameter is normally taken as

0.8

The oxygen absorption rate can be determined by a. Sodium sulfite oxidation method b. Dynamic gassing out technique c. Direct measurement d. All of these

d. All of these

Industrial paddle agitators turn at the speed of

20 and 150 rpm

The dynamic technique is based on the

Oxygen material balance in an aerated batch fermenter during the growth of microorganisms.

The addition of antifoams to an aerated bioreactor will decrease oxygen transfer rates because antifoams a. Increase the tendency of bubbles to coalesce. b. Tend to accumulate in the gas liquid interface. c. Reduce the surface tension of the liquid. d. All of the above answers.

d. All of the above answers.

During fermentation, the saturation concentration of oxygen was reduced from 7 ppm to 1 ppm. Which one of the following conclusions can be drawn? a. Microbial growth is oxygen limited since the oxygen concentration is lesser than the saturation concentration. b. Microbial growth is not oxygen limited since the oxygen concentration is lesser than the saturation concentration. c. Experimental error leads to the reduction. d. No conclusion can be drawn.

d. No conclusion can be drawn.

If the stirrer speed is too slow, bubbles will accumulate and coalesces under the impeller. This phenomenon is known as a

Flooded impeller

The maximum solubility of the alkane in the medium is 5 ppm. If the actual dissolved concentration of the alkane in the medium is 1 ppm. What conclusion may be drawn? a. The growth rate is limited by the rate of mass transfer of the alkane into the fermentation medium. b. The growth rate is limited by the intrinsic kinetic properties of the cells and not by mass transfer. c. The growth rate is neither mass transfer nor kinetically limited. d. No conclusion on the growth rate can be withdrawn.

d. No conclusion on the growth rate can be withdrawn.

Reynolds (Rei) number for the impeller is given by (where Di), stirrer diameter; N, stirrer speed; ⍴, density of fluid; and µ, viscosity of fluid).

Di^2 Nρ/μ

The advantage of axial flow impellers over radial flow impellers is that axial flow impellers

Provide better lift of solids.

Larger propellers turn at the speed of

400 to 800 rpm

A microbial population in a suspension culture will only be limited by oxygen availability if the dissolved oxygen

Concentration is less than the critical concentration.

Which of the following model holds correct for the two-film theory? (where KL is the mass transfer coefficient, DAB diffusivity and Zf film thickness)

KL = DAB /Zf

A fermentation system has a KLa of 3 s-1 and a CO* of 5 ppm of O2. If the bulk liquid is completely depleted of oxygen, then the oxygen transfer rate will be equal to

15 mg L-1 s-1

During aeration, a cylindrical reactor had a height of 10 m. Without aeration, the height was 7.5 m. Under these aeration and mixing conditions, the gas hold up in the reactor is

25%

A fermentation system has a KLa of 3 s-1 and a CO* of 5 ppm of O2. If the bulk liquid is saturated with oxygen, then the oxygen transfer rate will be equal to

Zero

Which of the following would be best described as radial flow impeller? a. An impeller with blades pitched at 45° to the vertical. b. A Rushton turbine c. Both (a) and (b) d. An impeller which directs liquid flow towards the base of the reactor.

b. A Rushton turbine

Small propellers turn at the speed of either

1150 rpm or 1750 rpm

In aerobic microorganisms cultures radial flow impellers are used because

They provide high shear mixing conditions.

The effect of increasing the stirrer speed in an unbaffled stirred tank reactor is that

As the stirrer speed increases, the liquid will continue to circulate. Eventually a vortex will form.

Turbulent flow range of mixing speed is obtained for

Rei > 10^4

For laminar flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei is Reynolds number for agitator; Di, stirrer diameter; and N, stirrer speed).

Np = K (Rei)^-1

For turbulent flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei is Reynolds number for agitator; Di, stirrer diameter; and N, stirrer speed).

Np = K

In a bioreactor, if at a particular time the oxygen transfer rate is 23 kg h-1, then the oxygen uptake will be

23 kg h-1

Axial flow impellers a. Provide high shear conditions for breaking up bubbles. b. Provide low shear conditions and are suited for use in shear sensitive processes. c. Provide direct flow towards the walls of the reactor. d. None of the above

b. Provide low shear conditions and are suited for use in shear sensitive processes.

Bioreactors, where vortex is formed, another dimensionless number, ___ is useful.

Froude

Oxygen transfer rate is increased with an increase in the stirrer speed in aerated bioreactor because a. It decreases the bubble size. b. It decreases the size of the boundary layer surrounding a bubble. c. It increases the rate of movement of oxygen molecules through the bulk liquid. d. All of the above.

d. All of the above.

If the stirring speed increased from 300 to 500 rpm leads to an increase in the reaction rate by two folds. Then it may be concluded that

The reaction was mass transfer limited at 300 rpm.

An increase in the heat transfer in the stirred tank reactor will be observed at

Higher stirrer speed.

In a two-phase system where the continuous phase remains in place, the gas hold up can be expressed as (where VS and Vt are the superficial gas velocity and bubble rise velocity).

H = Vs/(Vs+Vt)

What is the effect of the concentration of dissolved salts and sugars on the oxygen transfer rate? a. The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate. b. The KLa of the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate. c. The KLa of the medium increases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate. d. None of the above.

a. The saturation concentration of oxygen in the medium decreases with the concentration of dissolved salts and sugars, leading to a lower oxygen transfer rate.

Which of the following impellers generate a flow parallel to the axis of shaft? a. Axial flow b. Radial flow c. Both (a) and (b) d. None of these

a. Axial flow

In a tall reactor, oxygen transfer rates will be

Highest at the base of the reactor.

Which of the following impeller is used in situations where strong vertical currents are desirable for heavily suspending particles? a. Propeller b. Paddle c. Turbine d. None of these

a. Propeller

Laminar flow range of mixing speed is obtained for

Rei < 10

Which of the following number is calculated from the diameter and peripheral speed of the impeller?

Reynolds number

A higher liquid height will lead to a higher gas hold up by which the oxygen transfer rate will be

Higher at the base of the reactor.

The main function of the dimples provided in the cooling jacket is to a. Increase the level of turbulence of the cooling water in the jacket. b. Increase the residence time of the cooling water in the jacket. c. Increase the cooling water-jacket wall boundary layer size. d. All of the above.

Increase the level of turbulence of the cooling water in the jacket.

The power required by an agitator operating in a gas-sparged system is a. Lesser than the power required by an impeller in operating at same speed in a gas free system. b. More than the power required by an impeller in operating at same speed in a gas free system. c. Same as the power required by an impeller in operating at same speed in a gas free system. d. None of the above.

a. Lesser than the power required by an impeller in operating at same speed in a gas free system.

Which of the following will have the largest interfacial area per unit volume? a. A bubble with a diameter of 1 mm. b. A bubble with a diameter of 5 mm. c. A bubble with a diameter of 15 mm. d. A bubble with a diameter of 50 mm.

a. A bubble with a diameter of 1 mm.

Which device is commonly used for measuring the rate of rotation (rpm) of the stirrer shaft?

Tachometer

The specific death rate of an organism can be expressed as

ln(2)/D

The interception efficiency can be expressed as (where dP is the particle diameter and DC cylindrical collection diameter).

dp / Dc

The relationship between the del factor, temperature and time is given as

∆ = A.t.e^(E/RT)

The del factor (∆) increases as the final number of cells

Decreases

The overall del factor (∆) may be represented as

∆cooling = ∆heating + ∆holding + ∆cooling

The filter material used for air filtration system is/are a. Glass wool b. Glass fibre c. Norite d. All of the above

d. All of the above

The deviation from ideal plug flow due to axial mixing can be described by the

Dispersion model

Glass fibers are favorable as a filter medium because they give a

Lower pressure drop and are less liable to wetting or combustion.

The collection efficiency by interception increases with the

Increasing particle size

For indirect heating, the plate and frame heat exchange is generally more effective than the shell and tube heat transfer due to its

Larger heat transfer area

The mechanism of air filtration in fibrous filter is a. Electrostatic attraction b. Impaction c. Interception d. All of the above

d. All of the above

If the packing density (α) is defined as the volume of the fiber unit volume of filter bed, the velocity with the filter void space is equal to (where V1 is velocity in fluid void space and V0 is undisturbed fluid velocity).

V = V0/(1-∝)

For the turbulent flow, the dispersion coefficient is correlated as a function of

Reynolds number

In sterilization process, spore of which of the following organism is considered as control? a. Bacillus subtilis b. Clostridium botulinum c. Bacillus stearothermophilus d. Aspergillus niger

c. Bacillus stearothermophilus

Analogus to the molecular diffusion, the xdirectional flux or microorganisms suspended in a medium due to the axial mixing can be represented as (where Jn is flux component ‘n’, cn is concentration of ‘n’)

Jn = -D dcn/dx

The typical size of particles collected by diffusion mechanism is

<0.5µm

The X90 value for a filtration system is

The depth required to reduce population by 90%.

The value of K a. Increases with increase in air velocity. b. Decreases with increase in air velocity. c. Increases to an optimum with increase in air velocity and decreases on further increase of air velocity. d. None of these

c. Increases to an optimum with increase in air velocity and decreases on further increase of air velocity.

Model proposed by the Friedlander, correlating the air filtration efficiency by impaction can be expressed as (where NSt is the Stokes number).

ηimp = 0.075Nst^1.2

The efficiency of fibrous filter by combined mechanism is given by (where ηimp, ηint, ηdif are the efficiencies by impaction, interception, and diffusion, respectively).

1- ηimp ηint ηdif

The heat conduction in dry air is

Less rapid than in steam

For laminar flow of Newtonian fluid through a smooth round pipe, the ratio of average fluid velocity to the maximum velocity is

0.5

The reduction of number of cells from 1010 to one will result into the del factor (∆) of

Sterilization can be carried out by a. Heat b. Radiation c. Chemical agents d. All of these

d. All of these

The collection efficiency by the inertial impaction mechanism is the function of

Stokes and Reynolds number

The heated medium passes through a holding section, which is usually maintained in

Adiabatic conditions

The highest temperature which appears to be feasible for batch sterilization is

121°C

The mechanical means of accomplishing sterilization of fermentation media/equipment is

Ultrasonic

The radius of the filter with a depth of 14 cm required for a volumetric airflow rate of 10 m3/min is approximately

0.6 m

The moist heat is more effective than the dry heat because the intrinsic heat resistance of vegetative cells is greatly

Increased in a dry state.

The destruction of microorganisms by steam may be described as

First order chemical reaction.

Typical aeration rates for aerobic fermentation are

0.5 – 1.0 vvm

The maximum desirable limit Bureau of Indian Standards (BIS) of lead in the drinking water is

0.05 mg/L

Zeolite softening process removes

Both temporary and permanent hardness of water.

Conventional tertiary treatment is

Chemical coagulation and flocculation

The maximum desirable limit (BIS) of total hardness (as CaCO3) in drinking water is

300 ppm

The chemical oxygen demand (COD) measures the

Amount of oxygen that would be removed from the water in order to oxidize pollution

Hardness of water does not

Make it unfit for drinking.

Permanent hard water may be softened by passing it through

Sodium hexametaphosphate

Zeolite used in zeolite softening process for the treatment of hard water gets exhausted after certain time of usage but can be regenerated by flushing it with

10% sodium chloride solution

Temporary hardness of water is caused by the presence of

Bicarbonates of calcium and magnesium

Secondary treatment uses ___ to consume wastes.

Microorganisms

Secondary treatment uses ___ to consume wastes.

Microorganisms

Application of quaternary ammonium compounds as sanitizing agents tends to

Increase the percentage of gram(-)ve rods on utensils.

Permanent hardness of water is caused by the presence of

Chlorides and sulfates of calcium and magnesium

According to BIS, the maximum permissible limit of dissolved solids in drinking water is

2000 mg/L

Acid used mostly for removal of milk stone

Nitric acid

Which of the following chemical is sometime added in the process of coagulation and flocculation? a. Aluminum sulphate b. Aluminum oxide c. Calcium chloride d. None of these

a. Aluminum sulphate

Which of the following physical method is used as germicidal in modern time for the treatment of drinking water?

UV radiation

Sanitizer used specifically for vitreous enamel are

Weak alkali with sodium silicate

Inhibitors are used along with sanitizer to

To prevent corrosion.

Sanitizers used for rubber made equipment are

Strong alkalis

Biological oxidation processes usually referred as biological treatment, are the most common form of

Secondary treatment

The maximum permissible limit (BIS) of turbidity in drinking water is

10 NTU

Sedimentation is a physical process used in wastewater treatment to

Remove particles that are more dense than water.

The ultimate source of water is

Rain and snow

Permanent hardness of water may be removed by the addition of

Soda ash

Both temporary and permanent hardness of water can be removed on boiling water with

Sodium carbonate

Lagoons may be characterized as a. Anaerobic b. Facultative c. Aerated d. All of these

d. All of these

Temporary hardness of water may be removed by adding

Calcium hydroxide

The maximum desirable limit (BIS) of mercury in the drinking water is

0.001 mg/L

From the following sanitizers which one comes under category of surface active agents?

Teepol

The purest form of naturally occurring water is

Rain water

Calgon is used for removal of

Permanent hardness of water

The water being used in dairy industry should contain not more than

5 proteolytic and/or lipolytic organisms per mL

The activated sludge process consists of returning a portion of the clarifier

Influent water entering the reactor.

The activated sludge process is sometime referred as

Fluid bed biological oxidation system.

BOD stands for

Biochemical oxygen demand

When temporary hard water is boiled, one of the substances formed is

Carbon dioxide

Zeolite softening process removes both temporary and permanent hardness of water. In this process, the calcium and magnesium present in water are precipitated as

Insoluble zeolites

The methods used for biological treatment are a. Lagoon b. Activated sludge process c. Oxidation ditches d. All of these

d. All of these

Both temporary and permanent hardness of water can be removed by

Distillation

Coliform bacteria in water is an indication of the presence of

Human feces

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Biochemical Engineering Flashcards

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