Question 1

The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is

Accepted Answer

Microorganisms such as Lactobacillus and others commonly called Lactic Acid Bacteria (LAB) grow it milk and convert into curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins.A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperature multiply, thus, converting milk to curd, which also improves its nutritional quality by increasing vitamin-B12 .

Question 2

Rising of dough is due to

Accepted Answer

Inoculation of kneaded flour with baker yeast; Saccharomyces cerevisiae produce CO2​ during the process of fermentation, causes puffing up of the dough and make it soft and spongy. It is used to make foods like idli, dosa, bread, etc.

Question 3

Waste water treatment generates a large quantity of sludge, which can be treated by

Accepted Answer

Sludge is further treated by anaerobic digesters. These are large heated tanks in which its chemical decomposition is catalysed by microorganisms.The liquid is treated by bacteria which breakdown the organic matter remaining in solution. It is then sent to oxidation ponds where heterotrophic bacteria continue the breakdown of the organics and solar UV light destroys the harmful bacteria. Chemical are not used in this treatment.

Question 4

Methanogenic bacteria are not found in

Accepted Answer

Methanogenic bacteria (that produce methane) are not found in activated sludge. The microbes present in the activated sludge are aerobic bacteria that grow rapidly and form flocs.During secondary treatment of wastewater it is in the digestors where other kinds of bacteria which grow anaerobically, digest the bacteria and the fungi in the sludge producing mixture of gases such as methane, hydrogen sulphide and CO2​ which form the biogas.

Question 5

Match the following column of bacteria and their commercially important products.Codes            A     B     C    D

Accepted Answer

Following is the list of bacteria and their commercially important products

Question 6

Match the following column of bioactive substances and their roles.Codes             A   B   C   D

Accepted Answer

Following is the column of bioactive substances and their rolesStatins produced by the yeast Monascus purpureus have been commercialised as blood cholesterol lowering agents.Cyclosporin A, produced by the fungus Trichoderma polysporum is used as an immunosuppressive agent in organ transplant patients.Streptokinase produced by the bacterium Streptococcus and modified by genetic engineering is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infaction leading to heart attack.Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry.

Question 7

The primary treatment of waste water involves the removal of

Accepted Answer

The primary treatment of waste water involves physical removal of both larger and small particles (stable particles) from the sewage through filtration and sedimentation. These are removed in stages; initially, floating debris is removed by sequential filtration.Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge and the supernatant forms the effluent. The effluent is taken for the secondary treatment.The primary treatment does not remove the dissolved impurities (a), toxic substances (c) and harmful bacteria (d).

Question 8

BOD of waste water is estimated by measuring the amount of

Accepted Answer

BOD (Biochemical Oxygen Demand) refers to the amount of the oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria.Other options (a) (b) and (c) are incorrect.

Question 9

Which one of the following alcoholic drinks is produced without distillation?

Accepted Answer

Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.

Question 10

The technology of biogas production from cow dung was developed in India largely due to the efforts of

Accepted Answer

Cattle dung is used for the production of biogas, commonly called gobar gas.The technology of biogas production from cow dung was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC). Other options (a), (b) and (d) did not play any role is this.

Question 11

The free-livings fungus Trichoderma can be used for

Accepted Answer

Trichoderma species are free-living fungi that are very common in soil. They are effective biocontrol agents of several soil borne plant pathogens other options are incorrect.

Question 12

What would happen if oxygen availability to activated sludge flocs is reduced?

Accepted Answer

Activated sludge microorganisms need oxygen as they oxidise wastes to obtain energy for growth. Insufficient oxygen will slow down or kill off aerobic microorganisms, make facultative organisms work less efficiently and ultimately lead to the breakage of flocs.It will also result in the production of the foul-smelling byproducts of anaerobic decomposition. So, sufficient oxygen must always be maintained in the aeration tank to ensure complete waste stabilisation.

Question 13

Mycorrhiza does not help the host plant in

Accepted Answer

(d) Fungi form symbiotic association with the roots of higher plants called mycorrhiza (VAM) e.g, Glomus.The fungal hyphae symbiont in these associations absorb phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and draught, and an overall increase in plant growth and development. Mycorrhiza does not help the host plant in increasing its resistance to insects.

Question 14

Which one of the following is not a nitrogen-fixing organism?

Accepted Answer

Pseudomonas is a dentrifying bacteria, which convert ammonia and nitrates into free nitrogen, i.e., these denitrifying bacteria are responsible to liberate free nitrogen in the environment through nitrogen in the environment through nitrogen cycle.Other options (a), (b) and (c) show nitrogen fixing organisms.Azospirillum and Azotobacter are free-living bacteria, which absorb free nitrogen from soil, air and convert it into salts of nitrogen like amino acids and enrich soil nutrients.Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments, many of which can fix atmospheric nitrogen, e.g., Nostoc, Anabaena, Oscillatoria, etc.

Question 15

Big holes in Swiss cheese are made by a

Accepted Answer

The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2​ by a bacterium named Propionibacterium sharmanii. Other options are in correct.

Question 16

The residue left after methane production from cattle dung is

Accepted Answer

The raw material for biogas production is excreta (dung) of cattle. The biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed.A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. Methanobacterium in the dung act on the bio-wastes to produce bio-gas. The gas produced is supplied to nearby houses by an outlet. Through another outlet, the spent slurry is removed to be used as manure.

Question 17

Methanogens do not produce

Accepted Answer

In the digesters (during secondary treatment of waste water), heterotrophic microbes (methanogens) anaerobically digest bacteria and fungi in sludge producing mixture of gases such as methane, hydrogen sulphide and CO2​ which form the biogas. The O2​ is not produced by methanogens.

Question 18

Activated sludge should have the ability to settle quickly so that it can

Accepted Answer

In the secondary treatment of waste water, when BOD of sewage has reduced, the effluent is passed into setting tank. Here, the bacterial flocs settle and the sediment is called activated sludge.A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digesters. That's why activated sludge should have the ability to settle quickly.

Question 19

Match the following columns.Codes     A   B  C  D

Accepted Answer

Ladybird is the very familiar beetle with red and black markings, used to get rid of Aphids.Fungi form symbiotic association, with the roots of higher plants called mycorrhiza, e.g., Glomus.A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma.Methanogens, particularly Methanobacterium, are found in cow dung. These bacteria grow anaerobically on cellulosic material and produce large amount of methane along with CO2​  and H2​ .

Question 20

Why does ‘Swiss cheese’ have big holes?

Accepted Answer

The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2​  by a bacterium named Propionibacterium sharmanii.

Chapter 10 : Microbes in Human Welfare