The domestic sewage in large cities  
1. When treated in STPs does not really require the aeration step as the sewage contains adequate oxygen.
2. Has very high amounts of suspended solids and dissolved salts.
3. Has a high BOD as it contains both aerobic and anaerobic bacteria.
4. Is processed by aerobic and then anaerobic bacteria in the secondary treatment in sewage treatment plants (STPs). 

A good producer of citric acid is 
1. Aspergillus
2. Pseudomonas
3. Clostridium
4. Saccharomyces 

What gases are produced in anaerobic sludge digesters?  

1. Methane and CO₂.
2. Methane, Hydrogen sulphide and CO₂.
3. Methane, Hydrogen sulphide and CO.
4. Hydrogen sulphide and CO₂. 

Match the following list of microbes and their importance.

    (a) (b) (c) (d)
1. (iii) (i) (iv) (ii)
2. (iii) (iv) (i) (ii)
3. (iv) (iii) (ii) (i)
4. (iv) (ii) (i) (iii)

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

Select the mismatch:  
1. Rhodospirillum - Mycorrhiza
2. Anabaena - Nitrogen fixer
3. Rhizobium - Alfalfa
4. Frankia - Alnus 

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

1. Methanobacterium : Lactic acid
2. Penicillium notatum : Acetic acid
3. Saccharomyces cerevisiae : Ethanol
4. Acetobacter aceti : Antibiotics

Conversion of milk to curd improves its nutritional value by increasing the amount of        

1. Vitamin B₁₂
2. Vitamin A
3. Vitamin D
4. Vitamin E 

Probiotics are     
1. live microbial food supplement
2. safe antibiotics
3. cancer-inducing microbes
4. new kind of food allergens 

Common cold is not cured by antibiotics because it is
1. caused by a virus
2. caused by a Gram-positive bacterium
3. caused by a Gram-negative bacterium
4. not an infectious disease