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Biochemistry > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is the Industrial definition of fermentation?

A

Any process that utilizes chemical change induced by a living organism or enzyme to produce a product

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2
Q

What is fermentation?

A

A natural process achieved
by microorganisms

Chemical process by which molecules such as glucose are broken down anaerobically

  • Extracting energy from carbohydrates, without electron acceptors (e.g. O2)
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3
Q

What are the 3 core processes of fermentation

A
  1. Obtaining the best biological catalyst for a specific function or process
  2. Create the best possible environment for the catalyst to perform
  3. Product processing – separation and purification of the essential products from the fermentation process
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4
Q

What is genetic engineering

A

a process that uses laboratory based technologies to alter the DNA makeup of an organism

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5
Q

What is the best biological catalyst

A

Whole microbe or isolated enzyme(s)

Whole microbe is usually more stable/convenient. Why?

Processes can also use plant / animal cell culture. Why use these cell cultures?

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6
Q

What characteristics of microbes make them ideal for industrial purposes?

A

Different microbes can
– Create different products
– Grow in different environments
– Use different energy sources

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7
Q

What are the characteristics of an industrial microorganism

A

Produces useable substances or a desired effect
– e.g. penicillin from fungus, bioremediation

Available in pure culture (usually)

Amenable to genetic manipulation

Grows quickly

Can be separated from product (usually)

Nonhazardous

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8
Q

What is the best possible environment for the catalyst to perform

A

Typically, a containment system or a bioreactor provides the optimum environment for the catalyst

Include appropriate growth medium, optimum temperature, air, pH, etc.

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8
Q

What is needed for downstream processing

A
  1. Separate the product
  2. Purify the product
  3. Dispose of the waste safely and inexpensively

The process must be rapid, efficient and result in a stable product

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9
Q

What are cells generally filled with?

A

A matrix of primarily macromolecules: proteins, nucleic acids, lipids and polysaccharides

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10
Q

What are the Key Cellular Structures of a cell

A

Cytoplasmic membrane
- barrier that separates the inside the cell from outside

Cytoplasm
- part of the cell enclosed within the cell membrane

Nucleus/Nucleoid
- store the genetic information of the cell

Ribosomes
- part of the cell that make proteins from amino acid

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11
Q

What are considered prokaryotes and eukaryotes?

A

Prokaryotic: Bacteria, Archaea

Eukaryotic: Algae, fungi, protozoans

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12
Q

Explain archaea

A
  • Prokaryotes
    – Most live in extreme environment
    – Protein synthesis process similar to that of Eukaryotes
    (transcription and translation)
    – Physiologically very diverse
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12
Q

Compare eukaryotes and prokaryotes

A

Eukaryotes
– Larger, more complex than prokaryotic cells
– Membrane-enclosed organelles
(Nucleus, mitochondria, chloroplast, golgi, ER)
– Usually two copies of each gene
– Cell division by mitosis
– DNA present in linear chromosomes, several per cell

Prokaryotes
– Smaller, simpler than eukaryotes
– Lack membrane-enclosed organelles (Don’t have a nucleus)
– DNA usually in single circular
chromosome (May also have plasmid(s))
– Usually one copy of each
– Cell division normally by binary fission

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13
Q

What is the definition of microbial diversity?

How are the different kinds of microbes distinguished?

A

The range of different kinds of unicellular organisms, bacteria, archaea, protists, and fungi.

By their differing characteristics
of:
-cellular metabolism
-physiology and morphology
-various ecological distributions and activities
-distinct genomic structure

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14
Q

What are eubacteria

A

True bacteria
* Very diverse
* Divided into 12 subgroups

Almost all Industrial bacteria found in two groups:
– Proteobacteria (negative)
– Gram positive Eubacteria

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14
Q

What are the two major subdivisions of Gram positive Eubacteria composed of?

A

Low guanine + Cytosine group:
– Proportion of this base pair in their DNA
Industrial eg. Bacillus, Clostridium, Lactobacillus, Staphyloccocus, Streptococcus and Mycoplasma

High guanine + Cytosine group:
– Contains the Actinomycetes
– Filamentous bacteria
Industrial eg. Streptomycetes, Corynebacterium, Mycobacterium,
Micrococcus

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15
Q

What are the 3 basic physiological types of archaea

A

– Halophiles : adapted to high salt concentrations
– Methanogens : methane producers
– Thermophiles : adapted to high temperatures
(Includes Barophiles: adapted to high pressure)

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16
Q

What is the difference between gram positive and gram negative bacteria

A

Positive:
-doesnt have an outer membrane
-thick peptidoglycan layer
-doesnt stain

Negative:
-contains a thin layer of peptidoglycan
-lipopolysaccharides
-contains an outer membrane
-stains purple

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17
Q

What are the different types of prokaryotic diversity

A

Structural:
– Fimbriae, pilli, capsules, slime layers (Attachment to solid surface, other cells or providing protection)

Spore (endospore) formation
– eg Bacillus,Clostridium

Metabolism
-use inorganic and organics sources for energy

Ecological
-exist in extreme and normal environments (ocean, ice, plants, animals, lakes , atmosphere, hot springs etc)

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18
Q

Explain the key features of Bacillus subtilis

A
  • Rod shaped chemoheterotrophs

– Facultative aerobes(gram positive)
(Soil, water, air, composing plant residue)

– Widely used for the production of industrial enzymes
* Amylase- starch modification
* Proteases- cleaning aids in biological detergents

  • Used for production of fine chemicals (Nucleosides, vitamins and amino acids)

-Some strains used in crop protection against fungal pathogens

-Cloning host for production of heterologous proteins

-Cells walls – 20-50 nm thick , Have 20-25 layers of peptidoglycan, May have flagellate

-Produce capsules containing D and L-glutamic acid units

-Form spores

-Vegetative cells divide by binary fission

-Nutrient deprivation initiate sporulation
(Spores dormant, Highly resistant to heat, radiation, harsh chemical treatments)
(Spores can remain viable for long time, germinate when conditions are favourable)

-Several members of the Bacillus genus have important industrial roles :Source of enzymes, insecticide, antibiotics (bacitracin, gramicidin and polymixin)

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19
Q

Explain the key features of E. coli (bacteria)

A

– Facultative anaerobes (gram neg.)

– Some strains caused food and water borne diseases

– Have rapid growth rate
(Population can double in approx 30 minutes)

– Cells short straight rods

– Used in molecular biological studies

– Used for the production of heterologous proteins

– Ideal host in gene cloning

– Carry out mix acid fermentation producing mainly lactate,
acetate, succinate and formate

– Outer Membrane
* More permeable than cell membrane
* Protect cells from detergents and antimicrobial agents

– Peptidoglycan and periplasmic space
* Have 1-3 peptidoglycan layer
* Periplasmic space contain proteins, chemoreceptors and enzymes
* Defense enzymes present here (penicillinase)

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20
Q

What are the general characteristics of Fungi (Chromosomes)

A
  • Fungal chromosomes:
    – relatively small
    – haploid except for diploid stage in sexual life cycle
  • Reproduce both sexually and asexually
  • Reproduce by spores
  • Spores may be blastospores, sporangiospores, conidiospores,
    zoospores, ascospores
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20
Q

What is the main eukaryote in the industry? What are its uses?

A

Fungi
– Diverse group of Eukaryotes
* Saprophytes, symbionts, animal and plant parasites

Industrial Uses:
– Few filamentous fungi used for industrial purposes
– Many secrete degradative enzymes-degrade polymers

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21
Q

What are the general characteristics of Fungi (hyphae)

A

Filamentous fungi:
– originate from hyphae or spores
– Hyphal mat= mycelium

– Hyphal cell wall
* 80-90% polysaccharide, lipids, protein
* Polysaccharide is mostly chitin; glucan, mannan

  • Septate hyphae
  • have cross walls
  • Aseptate mycelium
  • lack cross walls
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22
Q

What are the 4 classes of fungai

A

– Phycomycetes
– Ascomycetes
– Basidiomycetes
– Deuteromycetes

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23
Q

what are Phycomycetes

A
  • Simplest fungi
  • Subdivided into
    – Mastigomycotina: produce zoospores, motile spores
    – Zygomycotina: produce zygospores- not motile
  • Aseptate
  • Cell wall- cellulose, glucan or chitin
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24
Q

What are some of the Industrially important Phycomycetes

A
  • Mastigomycotina
    – Water molds, plant pathogens
  • Phythium and Phytophthora
  • Zygomycotina
    – Mucor, Rizomucor, Rhizopus species
    – All used in some traditional food fermentation
  • Whole cell and enzyme bioconversion
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25
Q

What are Ascomycetes

A
  • Largest group of fungi
  • Hyphae is septate
  • Asexual reproduction-have haploid conidiospores
  • Sexual spores – ascospores in an ascus (sac)
  • Include yeast
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26
Q

What are some industrial Ascomycetes

A
  • Yeast-used in many industrial fermentation process, baking
  • Other commercial/industrial members:
    – Neurospora -model organism in biology
    – Clavicep - alkaloids-ergot species
    – Edible species: Morchella species- morels,
  • Tuber species (truffles)
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26
Q

What are Deuteromycetes

A
  • Lack define sexual stage
  • Demonstrate parasexuality in some species
    – Important in genetic study and strain development
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26
Q

What are Basidiomycetes

A
  • Club fungi
  • Sexual spores: haploid basidiospores in basidia
  • Produce septate hyphae
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27
Q

What are some Industrially important Basidiomycetes

A
  • Agaricus bisporus
  • button mushroom
  • Edible mushroom
  • Smuts and rusts
    – Important plant pathogens
  • white rot
    – Wood rotting fungi
    – Used in biodeterioration and biodegradation
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28
Q

What are some Industrially important Deuteromycetes (aspergillus)

A
  • Many industrially important species
    – Aspergillus
    –molds on food etc
  • Animal and plant pathogens
    – A. flavus , Aflatoxins :toxic and cancerous
    – Para nasal sinus infection
  • Used in industrial fermentation eg sake production to break down starch to simple
    sugars for yeast to ferment into alcohol
  • Major source of citric acid
  • Used in the production of native and foreign enzymes eg glucose oxidase
    – Cephalosporium – plant pathogen, mostly wheat
    – Fusarium- plant pathogen, huge in barley
  • F. venenatum used as human food-microprotein in vegetarian diets
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28
Q

What are some Industrially important Deuteromycetes (Penicillium)

A
  • Antibiotic production
  • Cheese production
  • Used to improve the taste of sausage and ham
  • Used to produce enzymes-cellulase, protease, lipase,
    amylase
  • Used to produce citric, gluconic and tartaric acids
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29
Q

What are yeast

A
  • Unicellular
  • Heterotrophic-found in many habitats especially flowers
  • Use reduce carbon- acetate, inorganic N2 , mineral as energy source
29
Q

What are some Industrially important Deuteromycetes (Trichoderma)

A
  • Develop as a biocontrol agent against several plant pathogenic fungi
  • Use in the production of several enzymes – Cellulase, hemicellulase, chitinase, xylanas
30
Q

Explain the Yeast Life cycle

A

Asexual cell division – Involves budding of a daughter cell from a mother cell

31
Q

Explain the Yeast sexual reproduction

A
  • Involves haploid cells of 2 mating types
  • Mating pheromone mediated
  • Cells elongate/differentiating becoming specialize pear shaped gametes
  • Cells of opposite mating types in contact undergo plasmogamy and karyogamyforming diploid cell
  • Meiosis occurs- if conditions suitable
  • Producing 4 haploid nuclei
  • Nuclei incorporated into stress resistant ascospores with an ascus
32
Q

Explain Yeast as industrial organism

A

S. cerivisiae have GRAS status:
– Generally regarded as safe
– Use to produce alcoholic beverages, leaven bread
– Use as a model system in molecular genetic research

  • Replication, recombination, cell division, metabolism
  • Similar to higher Eukaryotes
    – Also used to produce fuel ethanol, single cell proteins
    Enzymes, heterologous proteins eg human insulin
33
Q

Environmental factors that
affect microbial growth

A
  • pH
  • Temperature
  • Oxygen
  • Solute and water activity
  • Pressure
34
Q

Environmental factors that
affect microbial growth (pH)

A

-Fungi tends to grow at lower pH (4-6) than most bacteria

-Most microbes are neutrophils
- 5.5 - 8.5

-Acidophiles:
- 1 - 5.5

-alkaliphiles:
- 7.5 - 11.5

35
Q

Environmental factors that
affect microbial growth (Temp)

A
  • Mesophiles:
    – optimum range 20-45 oC
    – minimum 15-20 oC
  • Psychrophiles:
    – optimum below 15 oC
    – often killed by room temperature
  • Thermophiles:
    – optimum above 50 oC
    – several algae, protozoan and fungal species have temperature
    maxima up to 55 oC
36
Q

Environmental factors that
affect microbial growth (oxygen)

A

Obligate aerobes:
-grow only in the presence of O2

Obligate anaerobes:
-cannot tolerate O2, exposure result in their death

Facultative anaerobes:
-function with or without O2, does best when O2 present

Aerotolerant:
-grow well in the presence or absence of O2 (ignore O2)

Microaerophiles:
-require some O2 for the biosynthesis of certain compounds, cannot grow at normal atmospheric O2 concentration (21%), require lower O2 levels of 2-10%

37
Q

Environmental factors that
affect microbial growth (Solutes and water activity)

A

Water available to microbes is measured as water activity (Aw)

– Ratio of vapour pressure of water surrounding the microbe / vapour pressure of pure water

– Represents water that is not bound to other molecules, which can support microbial growth

-Most bacteria cannot grow below an Aw of 0.9

-Most fungi grow between Aw of 0.6 and 0.7

38
Q

Environmental factors that
affect microbial growth (Pressure)

A
  • Microbes normally experience pressure of 1 atm (101.3kPa)
  • Higher pressures inhibit growth
  • Exception: many marine microbes, such as deep sea bacteria or archaea
    – Barophile (or piezophile):
    needs high pressure to grow
    – Barotolerant:
    survives at high pressure and less extreme environments
39
Q

Composition of a typical microorganism

A

Water 70–80%

Protein 15–18%

Polysaccharide 1–3%

Lipid 1–2%

Nucleic acids 3–7%

Inorganic salts 1–2%

40
Q

How is nutrient uptake done

A

-Nutrients must cross the membrane

-Rate limiting step in the conversion of raw materials to products

-Can be passive or active transport

41
Q

What is the utilization of high molecular weight materials

A

e.g. Lipids, polysaccharides

  • Some eukaryotes use phagocytosis
    – Polymer is engulfed into the vacuole
    – Not possible in microbes with rigid cell walls
42
Q

Explain the microbial growth curve phases

A

Lag phase
- no overall population growth
- cells adapting to new environment
- influenced by media composition, stress, inoculum characteristics
- age, concentration, viability

Exponential
- population doubling
- nutrients in excess
- log phase

Stationary
- rate of cell division = rate of cell death
- nutrients are limited
- some cells produce secondary metabolites (idiophase)
- not needed for primary growth (e.g. antibiotics)

Deceleration / death
- lack of nutrients or buildup of toxic metabolites

Long-term stationary
- environment continues to support a small population

42
Q

What is binary fission

A
  • Cell division produces identical daughter cells
  • Each time a cell divides is called a generation
    – generation time is an average
    – not all cells are in the same stage of growth
  • Both microbial cell population and biomass concentration have doubled
43
Q

What are the two types of fermentation systems?

A

Batch Culture:
-fresh medium or components fed
continuously or intermittently, batch volume increase with time
-subtrates start high and decrease over time
-products start small and increase over time

Continuous Culture:
-both remain the same concentration over time, substrates are always higher than products

44
Q

What are the limitations of batch vs. continuous cultures

A

Batch System:
- Never steady-state
- Downtime (cost) and labor (cost) for:
- adding fresh medium
- Sterilizing medium and fermenter
- Inoculation
- Harvest
- cleaning

Continuous System:
-More prone to infection
- More prone to spontaneous mutations

45
Q

What are the Microscopic counting methods

A
  • Hemocytometer (Petroff-Hauser or Neubauer chambers)
  • Used to measure cells in a suspension
  • Rapid method of counting microbes per mL
  • Does not distinguish living from dead cells
  • Samples must contain relatively high cell concentrations
46
Q

What are the two methods for monitoring microbial growth

A

– Direct methods:
* dry weight determination, cell counting

– Indirect methods:
* turbidity, spectrophotometry, estimation of cell components (RNA, DNA, or ATP), monitoring of carbon dioxide production or oxygen utilization

47
Q

What are the Turbidity or spectrometric techniques

A
  • Simple and rapid
  • Light scattered or absorbed is proportional to biomass
  • Construction of calibration curves from a standard cell suspension of known concentration is required
  • Particulate matter or highly coloured broth can interfere with results, interpretation
48
Q

What is Dry weight estimation (limitations)

A
  • Measures weight of both living and dead cells
    – Start with a known volume
    – Filter under vacuum through 0.2 – 0.45µm pore size
    – Rinse filter to remove media
    – Dry at 105°C
    – Results expressed as mg of cells/mL of culture
  • Limitations:
    – Non cellular material can be collected in the filter
    – Time consuming
    – Large sample volume needed
49
Q

What is a Electronic cell counter

A
  • Draw cells in
  • As cells flow through opening in the sensor,
    resistance increases
  • Voltage = current x resistance (V=IR)
  • Records a spike in voltage as each cell passes
  • Works better with larger cells
50
Q

What is ATP Bioluminometry

A
  • Enzyme–substrate complex uses ATP from cells
  • Generates a photon of light for each molecule of ATP
    – Amount of ATP correlated to amount of viable cells
  • Light detected by bioluminometer
  • Coloured suspensions can interfere
51
Q

What does a good medium need for growth

A
  • Promote synthesis of product
    – Biomass
    – Primary metabolite
    (carbs, lipids, proteins, nucleic acids)
    – Secondary metabolite
    (alkaloids, phenolics, sterols, steroids, essential oils, lignins)

-makes up 80% production cost

51
Q

What is Online estimation

A
  • Most industrial microbes use O2 and produce CO2
  • Amount of biomass or can be estimated by measuring O2 and CO2 using detectors attached to a computer
  • Accuracy depends on reliable mathematical algorithms
52
Q

What are the 2 types of Isolation of suitable microorganisms from the environment

A
  • Shotgun approach
  • Objective approach
53
Q

What do cost effective substrates need to be?

A

– Inexpensive
– Readily available at consistent quality
– Easy and inexpensive to handle, transport, store (includes safety)
– Easy and inexpensive to sterilize (preferably by autoclave)
– Low foam
– Impurities do not generate undesired products

54
Q

Why is foam bad?

A
  • Usually caused by proteins in the medium
  • Undesirable:
    – Takes up space
    – Nutrients/products/microbes may float on the foam
    – Can block air filters
    – Can lead to contamination
54
Q

What is defined media vs undefined media

A
  • Defined medium
    – has known quantities of all ingredients
  • Undefined medium
    – contains some complex ingredients, which consists of mixtures in unknown proportions
    – Lower cost than pure chemicals
    – Often by-product of other processes
55
Q

How do you control foam?

A
  • Modify medium components
  • Mechanical foam breakers
    – Stir the foam above the liquid
    surface to break bubbles
  • Chemical antifoams
    – Plant oils
    – Silicon oils
    – Polyalcohols
    – Must be compatible
56
Q

What is a bioreactor?
Features?
Type?

A
  • A vessel ( closed system or culture system) that provides an optimal growth environment for cells
    – microorganisms, plant cells, animal cells
  • Features:
    – Can be sterilized (in place)
    – Control pH, temperature, oxygen, pressure, etc
  • Type depends on the fermentation process:
    – Aerobic vs Anaerobic
    – Stirred or Not Stirred
    – Batch vs Fed-Batch vs Continuous
    – Free Floating or Immobilized
57
Q

What is an inoculum

A

*“starter” culture

*May be 5-20% of the final size of the production fermentation

*Not usually in the same media as the production media

*Usually stored cells (lyophilized) used as initial starter, then slowly scale-up to final inoculum size

58
Q

Why use baffles?

A

Baffles are long, flat plates that attach to the side of the tank to prevent swirling & promote top to bottom fluid movement.

Baffles are used to prevent the undesirable flow pattern of swirling

58
Q

What are stirred tank reactors

A

Mixing method: Mechanical
agitation
* Require high energy input
* High shear forces may damage cells
* Baffles are usually used to reduce vortexing

59
Q

What are pneumatic systems (bubble column and airlift)

A

Mixing method: Gas sparging
* Low energy input
* Less shear than stirred tank
* Not good for viscous or foamy
liquids, or filamentous fungi

Mixing method: airlift
*Similar to bubble column, but with 2 distinct liquid steams: up-flowing and downflowing steams.

60
Q

What are hydrodynamic systems (packed-bed, trickle-bed and fluidized-bed)

A

Packed-Bed:
-Used with immobilized or particulate biocatalysts

-Medium can be fed either at the
top or bottom and forms a continuous liquid phase

Trickle-Bed:
-Variation of the packed bed reactor. Liquid is sprayed onto
the top of the packing and trickles down through the bed in small rivulets.

Fluidized-Bed:
-When the packed beds are operated in upflow mode, the bed expands at high liquid flow rates
due to upward motion of the particles.

61
Q

What are Photobioreactors

A
  • For photosynthetic culture
    – cyanobacteria, micro algae, plants
  • Need high surface to volume ratio for light access
  • May be open to atmosphere
    – e.g. open ponds etc
62
Q

what are solid state bioreactors

A
  • Little water
  • No continuous aeration
63
Q

How is Temperature Control done in bioreactors (refer to slide 3: 32)

A

Heat transfer surface area:
-Low in (a) external jacket and (b) external coil (for small biorecators)

-High in (c) internal helical coil and (d) internal baffle coil (for large reactors)

  • Easily adjustable in (e) a separate external heat exchange unit
64
Q

How is sterilization done in bioreactors

A
  • Thermal (preferred)
  • Chemical (for heat-sensitive equipment)
    – Alcohol
    – Bleach
    – Ethylene oxide gas
  • Radiation (for surfaces and liquids, expensive)
  • Filtration
65
Q

What are bioreactor materials?

A
  • Depends on purpose
  • Open tank made of wood… stainless steel
  • Lab scale – made of glass, so autoclavable
  • Pilot/Production scale – stainless steel so can withstand pressure
  • May be lined with coating so metals do not dissolve in media (corrosive product)
  • Welded well and free of pockets (cleaning)
66
Q

How do microbes utilize organic carbon?

A

– Glycolysis

  • Different glycolytic pathways can be used by different organisms:
    – Embden‒Meyerhof‒Parnas (EMP)
    – Entner‒Duodoroff
    – Pentose phosphate
  • Each is capable of generating energy and/or precursor molecules for use in other metabolic pathways.
67
Q

Microbial metabolism can be divided into primary and secondary processes. Explain each.

A

Primary Metabolism
* Req’d for growth and maintaining life
* Max production in log phase

Secondary Metabolism
* Not req’d for growth
* Usually end of log or stationary phase
* May be triggered by inducers (ex. AHL)
* Characteristic of a species
* Often coded on plasmids…can be lost (strain degeneration)
* Often many closely related pathways, complex structures

Other products
* In addition to primary and secondary metabolites:
– microbial cells or biomass (baker’s yeast)
– Enzymes
– Recombinant products
– Biotransformation
– Biopolymers

68
Q

Explain the EMP pathway of glycolysis

A
  • Divided into 2 phases
    – 6-carbon phase
    – 3-carbon phase
  • Produces ATP
  • Produces small precursor molecules for biosynthetic
    reactions
  • Found in all three domains; Bacteria, Archaea, and Eukarya

*producecs 2 pyruvate, 2 atp, and 2 NADH

69
Q

Explain the entner-duodoroff pathway in glycolysis

A
  • Useful for catabolism of carbohydrates that can’t be processed by EMP
  • Produces less ATP than the EMP pathway
  • Works sugars through a 6- carbon intermediate known as KDPG
  • Has been found in several aerobic and anaerobic bacterial species

*produces 2 pyruvate, 1 atp, 1 NADH and 1 NADPH

70
Q

Explain the Pentose phosphate
pathway of glycolysis

A
  • Technically NOT glycolysis
    – Doesn’t produce pyruvate
  • Produces carbon precursors for other pathways
  • Produces NADPH electron carriers for later use
  • Found in most microbial organisms

*produces 1 atp and 2 NADPH

71
Q

What are the final productions in each glycolysis method?

A

EMP:
-2 pyruvate
-2 ATP
-2 NADH

Entner-Duodoroff:
-2 pyruvate
-1 ATP
-1 NADH
-1 NADPH

Pentose Phosphate:
-1 ATP
-2 NADPH

72
Q

Respiration leads to the generation of much more ATP from the oxidation of NADH and FADH2. It requires oxygen or, as in some facultative and obligate anaerobic prokaryotes, another compound or ion that has a low redox potential, to act as the terminal electron acceptor.
What are the 3 possible compounds?

A

Nitrate respiration

Sulphate respiration

Carbonate respiration

73
Q

What happens when respiration is not an option?

A

Organisms must use an alternative
mechanism for the regeneration of the limited supply of coenzymes.
ex. Fermentation

74
Q

Explain how fermentation can be used instead of respiration.

A
  • Fermentation uses organic molecules to “get rid” of the electrons carried by NADH.
75
Q

Explain Lactic acid Fermentations

A

Lactic acid fermentation

  • Carried out by Gram-positive microbes known as “lactic acid
    bacteria” (LAB)

– Includes pathogens, normal flora of intestines, and microbes used to
make yogurt/sour cream

  • Heterolactic fermentation is slightly different.
  • It generates both lactic acid AND ethanol.

*Carried out by the LAB Leuconostoc

76
Q

Explain alcoholic fermentation

A
  • Carried out by yeast and some bacteria
  • Produces largely ethanol and CO2
  • Used for centuries by humans to
    produce beer and wine
  • Microbes die off as ethanol
    concentrations reach 12 to 15%
77
Q

Explain mixed acid fermentation*

A
  • Several bacteria and fungi produce a mixture of fermentation products.
  • Several have been adapted for
    commercial purposes:
    – Acetone production (nail polish remover)
    – Butanol production

Biochemistry (2 decks)

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