Introduction to Balanced Growth Flashcards
represents an approximation where the average cellular synthesis
activities are not affected by the growing cell population as the coordination is relatively
perfect.
Balanced growth kinetics
In an environment favorable for growth, cells regulate their metabolism and adjust the rates of various internal reactions so that a condition of_____________ occurs
balanced growth
Under balanced growth kinetics, the composition of the biomass remains
constant
the cell is able to modulate the effects of external perturbations and keep the biomass composition steady despite changes in environmental conditions.
balanced growth
For the biomass composition to remain constant during growth, the specific rate of production of each component in the culture must be equal to the __________
cell specific growth rate, ΞΌ.
Balanced growth cannot be achieved if environmental changes affect the
rate of growth
balanced growth occurs at the same time as
exponential growth
In _____________, the progressive doubling of cell number results in a continually
increasing rate of growth in the population.
unicellular organisms
A bacterial culture undergoing balanced growth mimics a
first-order autocatalytic chemical
reaction
the rate of the cell population increase at any particular time is proportional to the ____________ of bacteria present at that time
number density (CN)
The specific growth rate of the cells depends on the _________________ during growth and decline phases of batch culture
concentration of nutrients in the medium
a single substrate exerts a dominant influence on the rate of growth
growth-rate limiting substrate or, growth-limiting substrate
often the carbon or nitrogen source, although in some cases it is oxygen or another oxidant such as nitrate
growth-limiting substrate
the specific growth rate is related to the concentration of the growth limiting substrate by
Monod equation
Monod equation is proposed by _____ in ________
French biochemist Jacques Monod in 1942
this ________ type of equation was used to relate the growth rate of a microorganism culture to the prevailing feed concentration.
saturation isotherm
one of the most widely employed expressions for the effect of substrate concentration on specific growth rate
Monod equation
an empirical expression based on the form of
equation normally associated with enzyme kinetics or gas adsorption.
Monod equation
Monod equation has same form as the rate equation for an enzyme catalyzed reaction _________ and ________
Michaelis-Menten equation, Langmuir adsorption isotherm:
intrinsic parameters of the cell-substrate system
ππππ₯ and πΎs
According to the Monod equation, further increase in the nutrient concentration after π reaches ππππ₯ __________
does not affect the specific growth rate
Typical values of πΎπ are very small of the order of ________for carbohydrate substrates and
___________ for other compounds like amino acids
mg per liter, ππ per liter
The concentration of the growth-limiting substrate [S] in culture media is normally ________ than πΎs
much greater
_____ is assumed to be insignificant
πΎπ
___________ and ____________ as long as S remains greater than about ____, which is usually for most of the culture period
π β ππππ₯ and growth follows exponential kinetics, 10 πΎS
most frequently used expression relating growth rate to substrate concentration
Monod equation
Monod equation is valid only for _________ and should not be applied when growth conditions are changing rapidly.
balanced growth
At __________ levels, the Monod equation has limited applicability
low substrate
When growth is inhibited by ___________, extra terms can be added to the Monod equation to account for these effects.
high substrate or product concentrations
Alternative equations to Monod equation
Blackman equation, Tessier Equation, Moser equation, Contois equation
This refers to the metabolic needs of a cell to stay viable by consuming nutrients or converting intercellular materials
Endogenous Metabolism
During the _________, the cell catabolizes cellular reserves for new building blocks and for energy-producing monomers
stationary phase
an extension of the Monod model which gives way for a maintenance energy
Cell Maintenance
recognizes that generated energy by substrate consumption is not solely used in cell growth, but also in different functions
Cell Maintenance
represents the amount of substrate diverted from growth
π = specific maintenance rate
Other related forms of specific growth rate dependence
Tessier, Moser, and Contois
A model that describes the specific growth rate as a function of continuous substrate concentration.
Tessier Model
A model based on substrate concentration only
Moser Model
A model based on both substrate and biomass concentration.
Contois Model -
saturation constant
Ks
For Monod, the constants for the differential equation, a,b,k
0 2 1/πΎπ
For Tessier, the constants for the differential equation, a,b,k
0 1 1/K
For Moser, the constants for the differential equation, a,b,k
1 β1/π
1 +1/π
1/(πΎπ ^(1/n))
For Contois,the constants for the differential equation, a,b,k
0 2 1/πΎπx
binds to the active site and prevents the substrate from binding there
competitive inhibitor
binds to a different site on the enzyme; it
doesnβt block substrate binding, but it causes other changes in the enzyme so that it can no
longer catalyze the reaction efficiently
noncompetitive inhibitor
There are two main types of mathematical models of growth kinetics
structured and unstructured
simplest types of product formation kinetics arise when there is a simple stoichiometric connection between product formation and substrate utilization or cell growth
Unstructured models (UKM)
represent, from a simple global point of view, the metabolic behavior of
biomass cell production
Unstructured models (UKM)
In unstructured models, products are categorized into various types based on their relationship with microbial growth
Growth-associated products followed by Non-growth- associated products and Mixed-mode product formation.
The product is formed along with the growth of the microbial cells and product concentration is almost directly proportional to microbial
growth rate
growth-associated products
Formed by growing cells and hence primary
metabolites
Growth-linked products
In growth associated, That is product concentration __________with cell concentration
increases
In _____________, product formation is nowhere related to the growth rate of microbial cells but itβs a function of cell concentration and we can say that product formation and microbial growth rate are almost ___________to each other
non-growth associated products, inversely proportional
In many fermentations, especially those involving ___________, significant
product formation does not occur until relatively late in __________, perhaps
approaching or into the stationary phase.
secondary metabolites, batch cultivation
Fermentation of _________ follows the non-growth associated product
penicillin
In mixed mode, The product formation from the microorganism depends on both ____________
growth and non-growth associated
It takes place during growth and stationary phases
Mixed-mode
Mixed-mode is evident, especially in the
Leudeking Piret Model.
empirical relationship widely used to evaluate specific production rates of
some metabolites or other products in cultured cell
Leudeking Piret Model.
Leudeking Piret model is developed in _______ for ________ production in batch and continuous culture
1959, lactic acid
has proved extremely useful and versatile in fitting product formation data from many different fermentations
Leudeking Piret kinetics
This is the expected kinetic form when the
product is the result of energy-yielding metabolism, as in several anaerobic
fermentations
Leudeking Piret kinetics
The values of πΌ and π½ in _____________ determine the product formation kinetics of the cell.
Leudeking Piret kinetics
If πΌ = 0, the product is
non-growth associated
If π½ = 0, the product is
growth-associated
If πΌ β 0 and π½ β 0, the product is
mixed growth associated
introduced a classification of many of these
possibilities which serves to illustrate some possible cases
F. H. Deindoerfer
Deindoerferβs classification of fermentation patterns
simple, simultaneous, consecutive, stepwise
Nutrients converted to products in a fixed stoichiometry without accumulation of intermediates
Simple reactions
Nutrients converted to products in a variable stoichiometry without accumulation of intermediates.
Simultaneous reaction
Nutrients converted to a product with an
accumulation of an intermediate
Consecutive reactions
Nutrients completely converted to intermediate before conversion to product, or selectively converted to product in preferential order.
Stepwise reactions
Two important guidelines in writing structured product formation kinetics model
- all reactions should be expressed in terms of intrinsic concentrations
amount of a compound per unit cell mass or cell volume
intrinsic concentration
amount of a compound per unit reactor volume
extrinsic concentration
____________ concentrations cannot be used in kinetic expressions
Extrinsic
Synthesis of several microbial antibiotics and other secondary metabolites is inhibited by
high concentrations of phosphate.
The more accurately a kinetic description describes the actual chemical events that occur, the __________the kinetic model
more robust
the model is more likely to produce good results when applied to conditions other than those used to evaluate the model and determine its parameters
Robust
process by which cells make proteins.
Protein synthesis
Two stages of protein synthesis
transcription and translation
the transfer of genetic instructions in DNA to
mRNA in the nucleus
Transcription
Three steps under transcription
initiation, elongation, and termination.
After the mRNA is processed, it carries the instructions to a _____________ in the cytoplasm.
ribosome
Translation occurs at
ribosome
Assuming balanced growth, the rate of mRNA synthesis and rate of protein
synthesis are both
zero
To account for gene transcription modulation by an operator system, the __________ is introduced
promoter utilization efficiency
The rate of synthesis is proportional to the _________ and _________ with which this mRNA is utilized at the
ribosomes
concentration of mRNA coding for the protein and the efficiency
are those whose cells are not separated following cell division and so tend to grow in the form of βfilaments
Filamentous organisms
Example of filamentous organisms
molds
often form microbial pellets at high cell densities in suspension culture
Filamentous organisms
The growth models of molds should include the ___________ and
consumption of nutrients within the pellet at large pellet sizes.
simultaneous diffusion
can grow on the surface of a moist solid
filamentous cells
common example of kinetics of product formation and substrate utilization of molds and those of other filamentous microbes
Penicillin batch fermentation
For ___________ in a fixed batch time, there is an optimal initial substrate
concentration
maximum product yield
When there is an abundance of substrate, _______ occurs
fast fermentation
little product is formed and the substrate is primarily used for biomass production
fast fermentation
By minimizing branching in actively growing hyphae in the inoculum, product formation is
__________.
maximized
The__________ the degree of branching, however, the longer the lag phase and thus the
required batch time
smaller
substantially capable of predicting product formation
kinetic model of cell growth
Cell populations are typically _________with respect to individual cell size, age, growth
rates, and other properties
heterogeneous
The major disadvantage of ______________ models is their mathematical complexity
segregated kinetic
Cell division ___________ result in the production of two viable progeny.
does not always
if π© is ___________ then doubling time for a single cell is less than overall doubling time
not zero
may be used to calculate other frequency functions and average population properties with direct physical significance
age density function
Single cells may increase in mass while the total mass of the cell population increases
exponentially
The volume distribution which could be measured experimentally using a
Coulter counter or light-scattering flow cytometry measurements
Expresses the
specific product formation rate by cells that have spent a total time ΞΈ in the reactor by β π΄ππ
π βππΞΈ
π=1
.
product formation model of Ping Shu
