Question

Which is not a bacterial action?
A. Nitrogen fixation
B. Emulsification of fat
C. Sewage disposal
D. Ripening of cream

Answer 1

Microbes like Bacteria serve a variety of beneficial uses and are considered to be economically important microorganisms which are used by humans effectively. These microbes play a significant role in the field of producing traditional food, agriculture and also for medical purposes. Thus the occurrence of microbial action is one of the essential components for life.

Complete answer:
Nitrogen fixation is a biological process which occurs when atmospheric nitrogen is converted into ammonia or related nitrogenous compounds in soil by an enzyme called nitrogenase with the help of nitrogen fixing bacteria such as species of Bacillus, Rhizobium or Azotobacter and thus made available for plants.
There are various bacteria which are also involved in the process of sewage disposal. Most importantly saprophytic aerobic bacteria helps to break down the dead organic substances into inorganic and organic byproducts. Such bacteria are commonly used in treatment of sewage by facilitating the decomposition process of organic matter.
During the process of ripening the cream, the bacteria from the species of Bacilli called Lactobacillales and other Lactic acid bacteria which is growing in the cream of milk are used. These bacteria help to convert lactose into acid and eventually results in the production of cultured butter as well as curdling of cream.
Bile salts are used as emulsifying agents in the process of digestion and emulsification of fat molecules which take place in the small intestine.

Hence, the correct answer is option (B).

Note: Currently, microorganisms are widely used in modern medicines for the manufacture of antibiotics, drugs, and vaccines. Most of the antibiotics that are made by bacteria such as Streptomyces are used in the production of vaccines for immunization against infectious diseases such as cholera, whooping cough, tetanus, diphtheria and typhoid fever.