CBSE Class 12 Biology Notes Chapter 10 Microbes in Human Welfare

Microbes are the smallest living things that are found everywhere and can only be seen with the help of a microscope. 

• These microscopic organisms are pathogenic in nature, but some microbes are considered useful for humans.
• Microbes include viruses, bacteria, fungi, protozoa and prions.
• Bacteria are unicellular microbes that are smaller in comparison to human body cells.
• These microorganisms are found in soil, water, air, human bodies, and the bodies of other animals and plants.
• There are various applications of microbes in human welfare, including usage in agriculture and environmental sustainability.
• These microorganisms are used for digestion, development of the immune system and the production of vitamin K.

According to the CBSE Syllabus 2023-24, the chapter on Microbes in Human Welfare comes under Biology and Human Welfare. Microbes in Human Welfare Notes will help students prepare for the CBSE Class 12 Biology Examination. The entire topic holds a weightage of 12 marks.

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Class 12 Biology Chapter 10 Notes – Microbes in Human Welfare

Microbes in Food Processing

• Microbes can be used in the preparation of various household food items.
• Saccharomyces cerevisiae is a type of yeast used for making bread in the home and in the food processing industry.
• Dough gets its fluffy appearance from the carbon dioxide generated during the fermentation process.
• Some of the microorganisms are used to prepare traditional drinks such as farm bear.
• Lactobacillus is the bacteria used in the preparation of curd from milk.
• Propionibacterium shermanii is the bacterium that produces Swiss cheese. 
• Most popular food items, idli and dosa, are prepared with the help of fermented rice by some bacteria.

Microbes in Industrial Production

• Microbes can be used in industries for a variety of purposes, which are as follows:

Beverage Production

• In beverage industries, microbes are used for the production of fermented beverages such as wine, beer, whiskey, brandy, and rum.
• Saccharomyces cerevisiae, also known as brewer yeast, is used for the fermentation of malted cereals and fruit juices to produce ethanol.

Antibiotics

• Antibiotics are a form of chemical substance that has revolutionized the healthcare industry.
• These substances are prepared on a large scale by inducing microorganisms in large tanks.
• They are prepared using microbes, which in turn are used to inhibit the growth of other microorganisms.
• Penicillin, the first antibiotic developed by Alexander Fleming, was used to treat soldiers during the Second World War.
• Cyclosporin, produced by trichoderma polysporum (fungus), is used as an immunosuppressive agent in organ-transplant patients.
• These antibiotics are used for the treatment of cholera, whooping cough, pneumonia and typhoid.

Microbes in Antibiotics

Microbes in Sewage Treatment

• Microbes in Human Welfare Notes will provide a thorough understanding of biogas and sewage treatment by the use of microorganisms.
• A large amount of sewage waste is produced every day in our country.
• This sewage waste contains various organic matter and pathogens.
• A large amount of sewage is treated in sewage treatment plants before discharging them into water bodies.
• The process is carried out in two stages, namely primary treatment and secondary treatment.

Primary Treatment

• Primary treatment is done to settle the particles by gravity and thus remove objects that can float.
• The process of filtration and sedimentation removes the small and large particles.
• Primary sludge and the supernatant are used to prepare sediments, which are then used to create the effluent utilized in secondary treatment.

Secondary Treatment

• In secondary treatment, effluent is kept in aeration tanks for agitation.
• During the process of agitation, aerobic microbes are converted into flocs.
• This will reduce the level of biological oxygen demand of the effluent.
• Biological oxygen demand refers to the amount of oxygen consumed by all organic matter, which corresponds to one litre of water consumed.
• After the reduction of BOD, the water is transferred to the settling tanks.
• The remaining sludge will be transferred to anaerobic sludge digesters.
• During the process, various gases like methane, hydrogen sulphide and carbon dioxide are produced.
• This mixture of gases is known as biogas or gobar gas.

Microbes in Sewage Treatment

Microbes as Biocontrol Agents 

• Biocontrol agents are used to control the growth of insects and pests.
• It is used to increase the production and yield of crops.
• Classical and biological bioagents are two types of biocontrol agents.
• Fungi, bacteria, predators, viruses and parasitoids are different types of agents.
• There are three ways by which microbes are used as biocontrol agents.
• First, determine the cause of disease in the host body, then fight with the germs in the host body.
• Lastly, biocontrol will kill the organisms within the host body.
• Bacillus thuringiensis is a type of biocontrol agent that is sprayed on vulnerable plants.
• B. thuringiensis is a type of agent used by genetic engineering to fight against insect pests.

Microbes as Bio-fertilizers

• Biofertilizers are organisms that are used to increase the nutrient quality of the soil. 
• They are used by farmers to increase growth-promoting substances in the soil.
• Bacteria, algae and fungi are the main source of biofertilizers.
• Rhizobium is used for the fixation of atmospheric nitrogen, which the leguminous plants later use.
• Azotobacter is used for nitrogen fixation, the development of antibiotics, and the increase of important plant substances.
• Cyanobacteria is another form of biofertilizer that is used in paddy crops.

There are Some important List Of Top Biology Questions On Microbes in Human Welfare Asked In CBSE CLASS XII