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1. MULTIPLE CHOICE QUESTIONS (MCQS) BANK
ON
Industrial Microbiology and
Fermentation Technology
By
Asst. Prof. Santosh Napte
Sambhajirao Kendre
Mahavidhyalaya, Jalkot
Microbiology By Santosh Napte

2. 1. Which of the following is not a criterion to create a media?
a) It should be able to produce the maximum yield of product
b) It should be able to produce the maximum concentration of product
c) It should be easily sterilized
d) It should permit the maximum rate of product formation, no matter how costly it is
Answer: d The medium should permit the maximum rate of product formation and it should be
cheap and easily available throughout the year. It should be able to produce high yield and high
concentration of the desired product.
2. Which of the following is absent in fermentation media?
a) Carbon b) Nitrogen
c) Agar d) Water
Answer: c The fermentation media consists of carbon sources, nitrogen sources, water, minerals,
antifoams, buffers, chelating agents, etc. Agar is the constituent of the nutrient media of the Petri
plate.
3. Which of the following is not a Carbon source?
a) Blackstrap molasses b) Corn molasses c) Beet molasses d) Yeast extract
Answer: d The yeast extract is a nitrogen source. Blackstrap, corn, beet molasses are the carbon
sources.

3. 4. Which of the following raw material is useful for the production of alcohol?
a) Waste liquor b) Molasses c) Starch d) Alkanes
Answer: b The molasses-like blackstrap molasses, beet molasses, corn molasses are useful in the
production of alcohol. Waste liquor, molasses, alkanes, etc. belong to the group of carbon sources.
5. Sulphite waste liquor is obtained from _______
a) Paper pulp industry b) Wood industry c) Liquor industry d) Sulphur production
Answer: a Sulphite waste liquor is obtained from the paper pulp industry which is useful for the production
of ethyl alcohol from Saccharomyces cerevisiae. It is the most important yeast for the production of
alcohol.
6. Which of the following is a by-product after starch extraction from maize?
a) Blackstrap molasses b) Hydrol molasses c) Corn steep liquor d) Beet molasses
Answer: c Corn steep liquor is a by-product after starch extraction from maize. It is also useful in alcohol
production. It was used in the production of penicillin while culturing Penicillium.
7. The screening is isolation and detection of microorganisms of interest.
a) True b) False c ) Not part of Microbiology d ) None of these
Answer: a Screening is the use of highly selective procedures to allow the detection and isolation of only
those microorganisms of interest from a large microbial population.

4. 8. Which of the following is NOT a criterion for the choice of an organism?
a) The organism must be genetically stable
b) The organism must be able to produce a high yield of product
c) The optimum temperature for the growth of an organism must be above 50°C
d) The organism must be able to grow in an easily available nutrient medium
Answer: c
The optimum temperature for the growth of an organism should be above 40°C. This reduces the
cooling costs in large scale fermenters. The microorganisms are chosen based on the rest three
criteria.
9. Full-form of ATCC is _________
a) American Type Culture Collection
b) Automatic Type Counter & Classifier
c) American Type Counter Collection
d) American Type Classifier and Collection
Answer: a
ATCC stands for American Type Culture Collection. It is a non-profit organization and a key
resource for medical research. It is the organization which has the largest department of Research
and Development.

5. ATCC's collections include a wide range of biological
materials for research, including cell lines, microorganisms
and bioproducts. The organization holds a collection of
more than 3,000 human and animal cell lines and an
additional 1,200 hybridomas. ATCC's microorganism
collection includes a collection of more than 18,000 strains
of bacteria, as well as 3,000 different types of animal
viruses and 1,000 plant viruses. In addition, ATCC
maintains collections of protozoans, yeasts and fungi with
over 7,500 yeast and fungus species and 1,000 strains
of protists.

7. 10. Which of the following method is not used in isolation and screening of desired
microorganisms?
a) Crowded plate technique b) Auxanographic technique
c) Enrichment Culture technique d) Hanging Drop technique
Answer: d
Hanging drop technique is used for motility testing of bacteria. The methods for isolation and
screening are a crowded plate, auxanography, enrichment culture and use of indicator dyes.
11. Which of the following method is useful for the isolation and detection of organisms having
the ability to produce antibiotics?
a) Crowded plate technique
b) Auxanographic technique
c) Enrichment Culture technique
d) Indicator dye technique
Answer: a
The Crowded Plate Technique is used for the detection and isolation of the organisms which are
antibiotic producers. The serial dilutions of soil are performed and spread on a Petri plate and
allowed to grow. The well-isolated colonies are antibiotic producers with the zone of inhibition.

9. 12. Which of the following shows the zone of inhibition when a particular organism is grown on a Petri
plate?
a) Growth Factor producers
b) Antibiotic producers
c) Organic acid producers
d) Amino acid producers
Answer: b
The Antibiotic producers show the zone of inhibition. It is the zone where only the growth of a particular
colony is observed whereas rest all colonies get degraded by antibiotics.
13. Which of the following method is useful for isolation and detection of organisms having the ability to
produce growth factors?
a) Crowded plate technique
b) Auxanographic technique
c) Enrichment Culture technique
d) Indicator dye technique
Answer: b
The Auxanographic technique is used for the detection and isolation of the organisms which are growth
factor producers. The growth factor-like amino acids, vitamins promotes the growth of auxotrophic
mutants.

10. 14. Which of the following method is useful for isolation and detection of organisms having the
ability to produce organic acids?
a) Crowded plate technique b) Auxanographic technique
c) Enrichment Culture technique d) Indicator dye technique
Answer: d
The use of Indicator Dye Technique is used for detection and isolation of the organisms which are
organic acid producers. The organic acid producers produce acid which changes the colour of
media and is thus detected easily.
15. Which of the following method proceeds with 2-plate preparation?
a) Crowded plate technique b) Auxanographic technique
c) Enrichment Culture technique d) Indicator dye technique
Answer: b
Auxanographic technique proceeds with 2-plate preparation. The 1st plate is used to isolate and
detect prototrophs whereas 2nd plate is used for identification of auxotrophs.
16. Which of the following plate is used to detect and isolate organic acid producers?
a) Phenol red plate b) Potato Dextrose Agar plate
c) MacConkey’s Agar plate d) Rose Bengal Agar plate
Answer: a Phenol Red plate is used to detect and isolate organic acid producers. The colour of
plate changes from red to yellow in the zone of organisms producing organic acid.

11. 17. Which of the following method is useful for detection and isolation of those microorganisms which are
capable of growing on a particular nutrient medium?
a) Crowded plate technique
b) Auxanographic technique
c) Enrichment Culture technique
d) Indicator dye technique
Answer: c
The Enrichment culture technique is useful for the detection and isolation of those microorganisms which
are capable of growing on a particular nutrient medium. For e.g., cellulose producers grow on nutrient
medium supplied with cellulose.
18. Which of the following procedure has a great application in strain improvement?
a) rDNA Technology b) Conjugation
c) Transformation d) Transduction
Answer: a The applications of rDNA Technology have resulted in the improvement of strains and it has
helped the organisms in producing products which they were not able to produce earlier.
19. The Induced mutations results in _________ formation.
a) A-A dimer b) C-C dimer c) T-T dimer d) G-G dimer
Answer: c
The mutations which are not spontaneous and are induced purposely on strain are called Induced
mutations. It results in the formation of T-T dimers. T-T dimer results in the formation of hydrogen bonding
between thymine bases.

16. 20. The Replica plate technique was used for _________
a) Isolation of auxotrophs b) Isolation of revertants
c) Isolation of analogue-resistant mutants d) Isolation of prototrophs
Answer: a
The Replica plate technique was used for the isolation of auxotrophs.
21. Which of the following is NOT the technique of preservation?
a) storage on agar slants
b) storage under liquid nitrogen
c) dried cultures
d) storage in water
Answer: d
The techniques of preservation include – storage on agar slants, storage under liquid nitrogen,
dried cultures, lyophilization. Storage in water is not a technique for the preservation of microbes.

17. 22. The preservation of agar slopes has an expiration of 6 months and the agar needs to be changed every
6 months. Which of the following can be used to extent sub-culturing to 1 year?
a) Paraffin oil
b) DMSO
c) Glycerol
d) Loamy Soil
Answer: a The agar slants can be covered by paraffin oil and the extension time can be increased from 6
months to 1 year. DMSO, Glycerol, Loamy soil are used in the preservation techniques for the preservation
of microbes more than decades.
23. What is the temperature of liquid nitrogen (°C)?
a) -150°C b) -122°C c) -194°C d) -196°C
Answer: d The temperature of liquid nitrogen is -196°C. It is used to store and preserve the microbial
culture for a decade or even more. The cryoprotectants are added to the culture suspension before adding
to liquid nitrogen.
24. Which of the following is NOT a cryoprotective agent?
a) DMSO b) Glycerol c) Ethylene Glycol d) Paraffin wax
Answer: d The cryoprotective agents like DMSO, 10% Glycerol, Glycol are the agents that are added to
microbial cell culture to protect the cells at a lower temperature or in liquid nitrogen at -196°C.

18. 25. Which of the following is NOT the technique of preservation?
a) storage on agar slants
b) storage under liquid nitrogen
c) dried cultures
d) storage in water
Answer: d
The techniques of preservation include – storage on agar slants, storage under liquid nitrogen, dried
cultures, lyophilization. Storage in water is not a technique for the preservation of microbes.
26. During the preservation of microbial cell culture ______
a) metabolism stops b) metabolism continues
c) metabolism changes d) physiology changes
View Answer
Answer: b
The preservation of microbial cell culture does not alter the metabolism of microbes. Metabolism
continues. The microbial culture is active viably and dividing during the preservation.
27. Which of the following method of preservation is more suitable and used widely?
a) Dried Cultures b) Lyophilization
c) Salt Storage d) Storage in liquid Nitrogen
Answer: b
Lyophilization is the process of freeze-drying which involves sublimation of cell water and can be used to
store culture for about 25 years.

22. 28. What is the basic function of the fermenter?
a) To sterilize the medium
b) To recover the product
c) To provide optimum growth conditions to organisms and obtain the desired product
d) To purify the product
Answer: c
The main function of the fermenter is to provide the optimum growth conditions for the growth
of microorganisms and obtain the desired product. The recovery and purification of the product
are the parts of downstream processing.
29. While constructing the fermenter, which of the following is not required?
a) High-speed Agitation and Aeration system
b) Temperature control system
c) pH control system
d) Sample facilities
Answer: a
In designing and constructing the fermenter, the fermenter must be provided with adequate
aeration and agitation system. The agitation speed should not be higher and must not cause
damage to the microorganisms.

23. 30. The purpose of aeration is to provide ___________
a) The medium to organisms
b) The carbon dioxide to organisms
c) The oxygen to organisms
d) The water to organisms
Answer: c
The main function or purpose of aeration is to provide oxygen to the microorganisms for
metabolic requirements. It is the major process of the fermentation process.
31. The Aeration is mainly provided to organisms present in _______
a) Submerged culture
b) Solid State culture
c) Surface culture
d) Batch culture
Answer: a
The aeration is mainly provided to the microorganisms present in submerged culture. The
microorganisms in the submerged culture grow beneath the fermentation media and thus are in
less contact with oxygen. Therefore, aeration system is required.

24. 32. The agitator is required to _________
a) Provide air b) Mixing objectives
c) Purify the product d) Sterilize the media
Answer: b The agitator is required to achieve a number of mixing objectives, e.g. oxygen transfer, heat
transfer, fluid and gas-mixing, and maintaining a uniform environment throughout the vessel contents.
33. Which of the following is not the component of aeration and agitation system?
a) Impeller b) Baffles c) Stirrer gland and bearing d) Thermometer
Answer: d The structural components of the fermenter involved in aeration and agitation are Impeller or
agitator, Baffles, Stirrer glands and bearing, and the sparger or the aeration system.
34. Which of the following is not the use of baffles?
a) Increase the effect of agitation
b) Improve aeration efficiency
c) Improve cooling capacity
d) Improve the fermenter capacity
Answer: d The Baffles are metal strips about one-tenth of vessel diameter attached to the wall. They
prevent vortex and improve aeration efficiency. Agitation effect is also increased using wider baffles. The
cooling coils are attached to the baffles to increase the cooling capacity.

25. 35. Which of the following additives are required for a better yield of the desired product?
a) Precursors
b) Regulators
c) Inhibitors
d) Growth Factors
Answer: a
Precursors are the components added in the medium for better yield of the desired product. It was
helpful in improving penicillin yields.
36. Which of the following is not a property of antifoams?
a) It should be active at low concentrations b) It should have fast action on an existing foam
c) It should be non-toxic to micro-organism d) It need not be sterilized
Answer: d
The antifoam should be active at low concentration, should have fast action on an existing foam and
should be non-toxic to the micro-organism and must be sterilized.
37. Which of the following is not a defoamer?
a) Amide waxes b) Oleic acid c) Organic phosphates d) Propanoic acid
Answer: d
Amide waxes, Oleic acid, Organic phosphates, Sulphonated oils, Silicone oils, etc. are the antifoaming
agents which are added to the medium.

27. 38. The Batch culture is a/an ______ culture system.
a) Open
b) Closed
c) Isolated
d) Semi-closed
Answer: b
The Batch culture is a closed culture system that contains an initial, limited amount of nutrients.
The Continuous culture is an open system where nutrients are added continuously whereas the
Fed-Batch culture is a semi-closed system.
39. A period during which the growth rate of cells gradually increases is known as _____
a) Lag phase
b) Log phase
c) Stationary phase
d) Deceleration phase
Answer: b
A period during which the growth rate of cells gradually increases is known as a log or exponential
phase. This is the period of maximum growth rate. This is usually the longest phase of the
microbial growth period.

28. 40. During batch fermentation, in which phase the microbes in the fermenter are adapting to the new
environment?
a) Lag phase b) Log or exponential phase
c) Stationary phase d) Death phase
Answer: a
Microbes in the fermenter show lag phase when they are introduced in the fermenter where they adapt
themselves for a particular environment. This is the phase where microorganisms prepare themselves and
produce necessary enzymes or the metabolites necessary for their growth.
41. The following figure shows the growth of typical microbial culture in batch conditions. What is A, B, C
and D?
a) A-lag phase, B-log phase, C-stationary phase, D-deceleration
b) A-log phase, B-lag phase, C-stationary phase, D-deceleration
c) A-deceleration, B-log phase, C-lag phase, D-stationary
d) A-lag phase, B-log phase, C-deceleration, D-stationary
Answer: d
The growth of microbial culture initiates with lag phase followed by a log phase followed by deceleration
phase and finally stationary phase. The microorganism has to pass through all these phases for normal
metabolism.