Free Man and His Environment MCQs with Answers

41. Which of the following is correctly matched for the product produced by them?

• A. Methanobacterium: Lactic acid
• B. Penicillium notatum: Acetic acid
• C. Saccharomyces cerevisiae: Ethanol
• D. Acetobacter aceti: Antibiotics

Explanation: S. cerevisiae is the primary industrial ethanol producer and is the most ethanol-tolerant natural yeast known, however, cannot metabolize xylose. S. stipitis can effectively ferment both glucose and xylose and, however, has low ethanol tolerance and requires oxygen for growth.

42. Which of the following is wrongly matched in the given table?

• A. (a)
• B. (b)
• C. (c)
• D. (d)

Explanation: Clostridium butylicum helps in the production of butyric acid. Candida lipolytic and Geotrichum candidum help in the production of lipases that are added to detergents for removing oily stains from laundry.

43. The guts of cow and buffalo possess

• A. Methanogen
• B. Cyanobacteria
• C. Fucus sp.
• D. Chlorella sp.

Explanation: Methanogens like Methanobacterium are found in the rumen (a part of the stomach) of cattle. A lot of cellulosic material is also available in the rumen. In the rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.

44. An alga that can be employed as food for human beings is

• A. Ulothrix
• B. Chlorella
• C. Spirogyra
• D. Polysiphonia.

Explanation: Chlorella is a single-celled chlorophycean alga with rich protein content. It is considered a source of SCP (single-cell protein) and also a food source during long space travel.

45. What gases are produced in anaerobic sludge digesters?

• A. Methane and CO2 only
• B. Methane, Hydrogen sulfide, and CO2
• C. Methane, Hydrogen sulfide, and O2
• D. Hydrogen sulfide and CO2

Explanation: The type of gases produced by microbial activity depends upon the microbes and the organic substrates they utilize. Certain bacteria, called methanogens, grow anaerobically on cellulosic material and produce a large amount of methane along with carbon dioxide. These bacteria are commonly found in the anaerobic sludge during sewage treatment. Other anaerobic bacteria involved in the process of anaerobic digestion produce other gases like ammonia and hydrogen sulfide.

46. A good producer of citric acid is:

• A. Clostridium
• B. Saccharomyces
• C. Aspergillus
• D. Pseudomonas

Explanation: Aspergillus niger produces citric acid, Clostridium butylicum produces butyric acid, Saccharomyces is used for the commercial production of ethanol and Pseudomonas produces alkaline proteases.

47. Microbe used for biocontrol of pest butterfly caterpillars is

• A. Saccharomyces cerevisiae
• B. Bacillus thuringiensis
• C. Streptococcus sp
• D. Trichoderma sp

Explanation: Biopesticides are those biological agents that are used for the control of weeds, insects, and pathogens. The microorganisms used as biopesticides are viruses, bacteria, protozoa, fungi, and mites. Some of the biopesticides are being used at a commercial scale. The most important example is the soil bacterium, Bacillus thuringiensis (Bt). Spores of this bacterium produce the insecticidal cry protein. Therefore, spores of this bacterium kill larvae of insects which eat them.

48. Monascus purpureus is a yeast used commercially in the production of

• A. Ethanol
• B. Streptokinase for removing clots from the blood vessels
• C. Citric acid
• D. Blood cholesterol-lowering statins.

Explanation: Statins are produced by the yeast Monascus purpureus which have been commercialized as blood­ cholesterol-lowering agents. It acts by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

49. A patient brought to a hospital with myocardial infarction is normally immediately given

• A. Penicillin
• B. Streptokinase
• C. Cyclosporin-­A
• D. Statins.

Explanation: Streptokinase (Tissue Plasminogen Activator or TPA) is an enzyme obtained from the culture of some haemolytic bacterium Streptococcus which is modified genetically to function as a clot buster. Therefore, it helps in clearing blood clots inside the blood vessels through the dissolution of intravascular fibrin during myocardial infarction.

50. A nitrogen­-fixing microbe associated with Azolla in rice fields is

• A. Spirulina
• B. Anabaena
• C. Frankia
• D. Tolypothrix.

Explanation: Azolla plays a very important role in rice production. Azolla and its nitrogen­-fixing partner, Anabaena, have been used as green manure to fertilise rice paddies and increase production. With the help of Azolla, rice can be grown year after year, several crops a year, with little or no decline in productivity; hence no rotation of crops is necessary.