Microbiology: An Introduction, 13e (Tortora et al.)
Chapter 28 Applied and Industrial Microbiology
28.1 Multiple-Choice Questions
1) A baker forgets to put yeast in his bread dough. Which of the following do you expect to
happen to the bread as a result?
A) It will take longer to bake.
B) Bacterial contaminants will now be able to grow.
C) The bread will not rise.
D) The bread will look normal but will be tough.
E) The bread will have a sour taste.
2) Spoilage of canned foods stored at high temperatures, accompanied by gas production, is
A) thermophilic anaerobic spoilage.
B) flat sour spoilage.
C) spoilage by mesophilic bacteria.
D) caused by acid-tolerant fungi.
E) putrefactive anaerobic spoilage.
3) Spoilage of canned foods due to inadequate processing, NOT accompanied by gas production,
is
A) thermophilic anaerobic spoilage.
B) flat sour spoilage.
C) spoilage by mesophilic bacteria.
D) caused by acid-tolerant fungi.
E) putrefactive anaerobic spoilage.
4) Which one of the following pairs is mismatched?
A) Propionibacterium – Swiss cheese
B) Penicillium – blue cheese
C) Lactobacillus – yogurt
D) Acetobacter – vinegar
E) Bacillus – beer
5) Which one of the following pertains to an improperly canned food product on a store shelf
that has a bad odor and putrefaction of the canned material?
A) mesophilic spoilage
B) flat sour spoilage
C) bacterial soft rot
D) thermophilic anaerobic spoilage
E) hydrogen sulfide spoilage
6) All of the following are fuels produced by microorganisms EXCEPT
A) cellulose.
B) ethanol.
C) hydrogen.
D) methane.
E) oil from algae.
7) Microorganisms play an active role in the formation of industrial products. Which one of the
following is mismatched?
A) Penicillium – treatment of disease
B) Saccharomyces cerevisiae – for fermentation
C) Rhizobium – increases nitrogen in the soil
D) Bacillus thuringiensis – insecticide
E) algae – citric acid
8) Which one of the following is an undesirable contaminant in wine-making due to its
production of vinegar rather than ethanol?
A) Acetobacter
B) lactic acid bacteria
C) Clostridium botulinum endospores
D) Saccharomyces
9) Commercial sterilization differs from complete sterilization in that commercial sterilization
A) kills all microorganisms.
B) kills only bacteria.
C) may result in the survival of thermophiles.
D) employs a higher temperature.
E) may result in the survival of fungal spores.
Figure 28.1
10) In Figure 28.1, assume the cells are your desired product and you want to maintain a
continuous culture. Remember, the top lines/markings indicate the different phases observed in
the curve below them. When would you harvest cells to maximize your yield?
A) a
B) b
C) c
D) d
11) In Figure 28.1, assume that a secondary metabolite is your desired product. Remember, the
top lines/markings indicate the different phases observed in the curve below them. When would
you be able to obtain it?
A) a
B) b
C) c
D) d
12) In Figure 28.1, assume the cells are producing penicillin which is collected during the
idiophase. Remember, the top lines/markings indicate the different phases observed in the curve
below them. When would you be able to collect the penicillin?
A) a
B) b
C) c
D) d
13) Which one of the following reactions is performed by yeast in wine-making?
A) sugar → ethanol
B) ethanol → acetic acid
C) malic acid → lactic acid
D) carbon dioxide → sucrose
E) sugar → CO2 + H2O
14) Which one of the following reactions makes wine less acidic, and is important for good
flavor when grapes with higher acidity are used?
A) sugar → ethanol
B) ethanol → acetic acid
C) malic acid → lactic acid
D) carbon dioxide → sucrose
E) sugar → CO2 + H2O
15) Commercial sterilization of processed canned foods uses a 12D treatment which is based
upon a theoretical population of 1012 C. botulinum endospores in a can of food. After treatment,
there would theoretically be how many endospores left?
A) 120 endospores
B) 10 endospores
C) 100 endospores
D) 12 endospores
E) 1 endospore
16) All of the following are advantages of a bioreactor instead of a flask culture EXCEPT
A) larger culture volumes can be grown.
B) instrumentation for monitoring environmental conditions.
C) uniform aeration and mixing.
D) aseptic sampling.
E) None of the answers is correct; all of these are advantages of using a bioreactor instead of a
flask culture.
17) Microbial products can be improved by all of the following EXCEPT
A) isolating new strains.
B) mutating existing strains.
C) genetically modifying strains.
D) modifying culture conditions.
E) sterilization.
18) Which of the following microorganisms is usually used in the fermentation of alcoholic
beverages?
A) Propionobacterium
B) Lactobacillus
C) Rhizopus
D) Saccharomyces
E) Penicillium
19) All of the following are true of irradiation methods used for food preservation and
sterilization EXCEPT
A) they prolong shelf-life of fruits and vegetables.
B) residual radioactivity is left behind on many foods.
C) ionizing radiation such as X rays or gamma rays is used.
D) they are used for the sterilization of many spices.
E) they greatly reduce the number of pathogens present in meats and poultry.
20) All of the following are industrial products produced in very large amounts by microbes and
then purified for use EXCEPT
A) amino acids in food supplements.
B) antibiotics.
C) industrial enzymes.
D) wine.
E) vitamin B12 and riboflavin.
21) All of the following are industrial products produced using microbial fermentations EXCEPT
A) aspartic acid.
B) citric acid.
C) glutamic acid.
D) riboflavin.
E) saccharin.
22) All of the following foods are produced using microbial fermentations EXCEPT
A) sauerkraut.
B) ketchup.
C) sour cream.
D) yogurt.
E) coffee.
23) Which of the following microbes produces a natural biopesticide?
A) Penicillium chryssogenum
B) Saccharomyces cerevisiae
C) Bacillus thuringiensis
D) Lactobacillus buggaricus
E) Thiobacillus ferroxidans
24) Biomass is a renewable energy source derived from the organic matter produced by living
organisms. All of the following are sources of biomass EXCEPT
A) oxidation of metals.
B) crops.
C) bacteria.
D) landfill sites.
E) algae.
25) All of the following are industrial enzymes made by microbial fermentations EXCEPT
A) glucose isomerase.
B) rennin.
C) proteases.
D) amylases.
E) vitamin C.
26) What process does yeast use to produce ethanol for automobile fuel from corn?
A) anaerobic respiration
B) fermentation
C) the Krebs cycle
D) oxidation
E) photosynthesis
27) The following steps are required for making cheese. What is the second step, which helps to
provide the characteristic flavors and aromas of the cheese?
A) enzymatic coagulation of milk
B) fermentation of curd
C) inoculation with lactic acid bacteria
D) inoculation with Penicillium
E) separation of curds and whey
28) As cheese ages, it gets
A) more acidic.
B) more whey.
C) more protein.
D) saltier.
E) more alcoholic.
29) Acidithiobacillus ferrooxidans is used for the recovery of ________ from ore.
A) sulfur
B) copper
C) iron
D) sulfuric acid
E) gold
30) What role do lactic acid bacteria play in cheese production?
A) curd formation
B) production of holes in Swiss cheese
C) ripening the cheese
D) providing characteristic flavor and smell
E) Lactic acid bacteria carry out each of these roles in cheese production.
31) You are growing Bacillus subtilis, an aerobic bacterium that can also carry out fermentation,
when required, in a bioreactor and notice that the growth rate has slowed and the pH has
decreased. You suspect the bacteria are
A) using the Krebs cycle.
B) fermenting.
C) photosynthesizing.
D) using proteins.
E) dead.
32) You are growing Bacillus subtilis, an aerobic bacterium that can also carry out fermentation,
when required, in a bioreactor and notice that the growth rate has slowed and the pH has
decreased. What could you add?
A) glucose
B) lactose
C) peptides
D) oxygen
E) lactic acid
33) Aseptic packaging utilizes which of the following to sterilize laminated paper or plastic prior
to filling with food?
A) hot HCl solution
B) gamma radiation
C) hot hydrogen peroxide solution
D) X rays
E) autoclave
34) All of the following are uses for ionizing or ultraviolet radiation EXCEPT
A) heating cold food.
B) sterilizing spices.
C) inactivation of Trichinella larvae.
D) killing of insect eggs and larva.
E) prevention of sprouting.
35) Canning preserves food
A) through use of aseptic packaging.
B) by exposure to chemicals.
C) by exposure to high heat.
D) by exposure to radiation.
E) by exposure to high pH.
36) Microorganisms themselves are commercial products. Which of the following microbes is
available as (or in) a product sold in retail stores?
A) Bacillus thuringiensis
B) Lactobacillus
C) Rhizobium
D) Saccharomyces
E) All of these organisms can be found in various commercial products.
Figure 28.2
37) Figure 28.2 shows the growth curves of Acetobacter under different conditions. Which
culture would produce the highest amount of the primary metabolite acetic acid?
A) a
B) b
C) c
D) d
E) e
38) Which of the growth curves in Figure 28.2 will give the highest yield of a secondary
metabolite?
A) a
B) b
C) c
D) d
E) e
39) Which of the growth curves in Figure 28.2 is indicating the culture has reached the
trophophase?
A) a
B) b
C) c
D) d
E) e
40) Which of the growth curves in Figure 28.2 is indicating the culture has reached the
idiophase?
A) a
B) b
C) c
D) d
E) e
41) Canning works to preserve foods through
A) creation of an anaerobic environment.
B) creation of an anaerobic environment and exposure to high heat.
C) exposure to high heat.
D) mutation of bacterial DNA.
E) increasing pH.
42) Aseptic packaging of non-metal containers (where the packaging itself is rendered sterile)
helps to preserve foods through
A) creation of an anaerobic environment in the packaging.
B) creation of an anaerobic environment in the packaging and exposure of the packaging to high
heat/hydrogen peroxide.
C) exposure of the packaging to high heat/hydrogen peroxide.
D) mutation of bacterial DNA by exposure to the packaging material.
E) increasing pH in the food contained in the packaging.
43) Radiation works to preserve foods through
A) creation of an anaerobic environment.
B) creation of an anaerobic environment and high heat.
C) exposure to high heat.
D) lethal mutation/destruction of bacterial DNA.
E) increasing pH.
44) All of the following are reasons for utilizing algae for biofuel production EXCEPT
A) they do not take up land needed for food production.
B) they produce more energy per acre than corn.
C) their main requirement is abundant light.
D) they can utilize agriculturally poor land.
E) they produce a nondegradable waste product.
45) What will be produced if wine is aerated and inoculated with bacteria of the genera
Acetobacter and Gluconobacter?
A) ethanol + CO2
B) CO2 + H2O
C) CH4
D) acetic acid
E) None of the answers is correct.
46) Bioreactors are widely used for industrial fermentation. Which of the following conditions
must be closely monitored for optimal fermentation?
A) temperature
B) oxygen levels
C) pH
D) both temperature and pH
E) temperature, pH, and oxygen levels
47) Xanthan used in household products is produced by bacteria
A) that were genetically modified.
B) that were irradiated to mutate them.
C) selected for their ability to utilize lactose rather than glucose.
D) that are plant pathogens.
E) selected for their ability to utilize lactose rather than glucose and that are plant pathogens.
48) The field of study related to study of small molecule chemical fingerprints of cellular
processes is known as
A) metabolomics.
B) bioconversion.
C) fermentation.
D) food preservation.
E) biofuel production.
49) Pascalization is
A) the use of extremely low pressure as a food preservation method.
B) the leeching of valuable metals out of ore via microbial processes.
C) use of damaging ionizing radiation for sterilization of food or other items.
D) the use of extremely high pressure as a food preservation method.
E) a microbial process that allows for production of biofuels.
50) Which one of the following is NOT an advantage of the food preservation method known as
pascalization?
A) It prevents concerns regarding irradiation.
B) It requires strong regulatory approval and oversight.
C) It preserves colors of foods well.
D) It preserves tastes of foods better than other methods.
E) It kills many pathogenic and nonpathogenic strains of microbes, improving food safety and
shelf life.
28.2 True/False Questions
1) The blue-green clumps observed in Roquefort cheese are a result of mold growth.
2) The longer interior-ripened cheeses are permitted to ripen, the milder the taste of the cheese.
3) Mesophilic bacteria grow best at temperatures of 60°C.
4) High-pressure processing of foods such as deli meats and precooked chicken strips targets
pathogens such as Salmonella and Listeria.
5) Rhizobium and Bradyrhizobium are mixed with peat moss to increase nitrogen fixation.
6) The production of vinegar relies on the microbial oxidation of ethanol to acetic acid.
7) Industrial canning, as opposed to home canning, is achieved using a pressure cooker which
operates in a manner similar to an autoclave.
8) A large industry exists based on the synthesis of amino acids by microorganisms.
9) If an industrial microbiologist works with Acidithiobacillus ferrooxidans, he is likely to be
involved in copper mining.
10) Vitamins C and B12 are commonly produced by microorganisms.
28.3 Essay Questions
1) Discuss the production of four different foods that require microbial fermentation in their
products. In your discussion, name the specific microorganisms used and describe the
fermentation by-product(s) needed for the production of each food item.
2) Discuss the production of three different non-food/beverage substances that utilize
microorganisms in their production. Your discussion should include the specific microorganisms
involved and their role in the production of each substance.
3) Explain how ionizing radiation can be used to preserve foods. Discuss its advantage over
canning as a method of preservation.
4) Vessels used for industrial fermentation reactions are known as bioreactors. Explain the
difference between batch production and continuous flow production using a bioreactor.
5) Use of fossil fuels is beginning to change in modern society. Describe what a biofuel is, and
identify/discuss the pros and cons of biofuels.