Microbes in Human Welfare Notes

CBSE Class 12 Chapter 8 Microbes in Huaman Welfare: Microbes are the smallest living organisms that can only be seen under the microscope. Microbes are found everywhere. Examples- are air, water, soil, inside and outside the bodies of plants and animals, thermal vents (1000 degree Celsius), under the layers of snow, and in acidic environments. All microbes are not harmful, some are very useful. Microbes are pathogenic in nature but some microbes are beneficial for humans.

Microbes in Household Products

Microbes can be used in many household products. Lactic acid bacteria/ LAB (Lactic Acid Bacteria) are used for curdling milk and to keep the fauna (healthy bacteria) of our gut healthy. Baker’s yeast (Saccharomyces cerevisiae) is used to ferment various foods eg. idli, dosa, bread, jalebi, etc. They are puffed and give a net-like appearance because of the production of carbon dioxide gas (the end product of fermentation). 

Toddy is a traditional drink which is consumed in some parts of southern India, made by the fermentation of sap in plants like palms. Large holes in ‘Swiss cheese is due to the production of carbon dioxide, released by Propionibacterium sharmanii (a bacterium)

Microbes in Industrial Products

Microbes are used in industries for various processes. Such as:

Fermented Beverages

In industries, the microbes are grown in fermentors (large vessels). Production of fermented beverages like wine, beer, whisky, etc. is done by a baker’s or brewer’s yeast- Saccharomyces cerevisiae. Ethanol production is done by the fermentation of malted cereals and fruit juices.

Antibiotics

These are the chemical substances, produced by some microbes and can kill/check the growth of other microbes. These control diseases like cholera, whooping cough, pneumonia, typhoid, etc. by killing the microbes responsible for such diseases. These are also used to preserve food like fresh meat/fish. The term antibiotic was first coined by Selman Waksman. Penicillin was the first antibiotic, discovered by Alexander Fleming which was used to treat the wounds of the American soldiers in World War II

Antibiotics	Microbial sources	Diseases which are treated
Penicillin	Penicillium notatum	Asthma
Erythromycin	Streptomyces sp.	pneumonia, TB
Streptomycin	Streptomyces griseus	Eye infections
vancomycin	Amycolotatepsis sp.	Diarrhoea
Chloromycin	Streptomyces Venezuela	Typhoid

Chemicals, Enzymes and Other Bioactive Molecules

There are various microorganisms are used to produce different enzymes and bioactive molecules:

Name of the Acid Producer	Classification	Acid/acids produced
Aspergillus niger	fungus	citric acid and oxalic acid
Acetobacter aceti	bacterium	acetic acid
Clostridium butylicum	bacterium	acetic acid
Lactobacillus	bacterium	butyric acid
Saccharomyces cerevisiae	yeast	ethanol

 Production and Uses of Enzymes

Name of the products/enzymes	Uses
Lipases	In detergent formulations To remove oily stains- used in laundry
Pectinases and proteases	To clarify juices(tetra-packs)
Streptokinase	Used as a ‘clot buster’ for removing blood clots in patients having heart diseases
Cyclosporin A (produced by a yeast- Monascus purpureus)	Used as an immunosuppressive agent in organ-transplant patients
Statins (produced by a yeast- Monascus purpureus)	Used as blood-cholesterol lowering agents (inhibits cholesterol producing enzyme)

Microbes in Sewage Treatment

Human excreta is the major component of wastewater. Sewage is municipal wastewater which contains organic matter and pathogens. Pathogens are disease-causing organisms. Sewage is treated in sewage treatment plants (STPs) before releasing into any water body. Two stages of sewage treatment:

1. Primary
2. Secondary

Primary Treatment

This treatment is done to settle material by gravity, removing objects which are floatable. In this treatment, small and large particles eg. floating debris are removed by filtration and in sedimentation, soil and small pebbles are allowed to settle for removal later. The settled solids form primary sludge and supernatants form effluents.

Secondary/Biological Treatment

In this treatment, the effluents produced in the primary treatment, are separated and kept in aeration tanks. Agitation is done mechanically and air is pumped into it. Aerobic microbes are grown in the form of flocs (mesh-like appearance when bacteria are grown with some fungi). Biochemical oxygen demand (BOD) is reduced because of the consumption of organic matter in the effluents by microbes. BOD is the amount of oxygen which is consumed when all the organic matter in one litre of water is oxidised/consumed by bacteria. If the BOD of waste water is more, it shows its pollution potential i.e. more polluted. When the BOD is reduced, effluent is passed into a settling tank where bacterial flocs settle down. This is called activated sludge. Some amount of activated sludge, the inoculum is pumped back into the aeration tank. These are known as anaerobic sludge digesters. Bacteria produce a mixture of gases (biogas/gobar gas) like Methane, hydrogen sulphide and carbon dioxide. After being treated, water is released into any of the water resources like ponds, rivers, streams, etc.

The Ministry of Environment and Forests has initiated some plans like the Ganga Action Plan and Yamuna Action Plan to save major rivers of our country from being polluted.

Microbes in the Production of Biogas

Some bacteria that produce methane are called methanogens eg. Methanobacterium which grows anaerobically (in the absence of air) on cellulosic material and produces a large amount of methane along with CO₂ and H₂

Location of Methanogens 

They are found in the anaerobic sludge (sewage treatment). They are also present in the rumen, a part of the stomach of cattle eg. cows, and buffalo. They break down cellulose and play an important role in the nutrition of cattle. Along with these, methanogens are also present in marshy areas.

Biogas Plant

It consists of a concrete tank in which bio-wastes are put and slurry is made. It has an outlet, which is connected to a pipe to supply biogas to nearby stations/houses for cooking and lighting. The spent slurry is removed through the second outlet and used as fertiliser. The technology of biogas production was developed by the efforts of the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC)

Microbes as Biocontrol Agents 

Biological methods are used to control plant diseases and pests. In modern days, it is done by the use of insecticides and pesticides which are toxic as well as harmful.

Biological control of pests and diseases

Integrated pest management programme (IPM)-some beneficial insects are being conserved to help in a programme

Name of the Microorganisms	Used to get rid of/control
Beetles with red and black dots (Ladybirds)	Aphids
Dragonflies	Mosquitoes
Bacillus thuringiensis (Bt- bacterium)	butterfly caterpillars
Trichoderma (fungus)	plant pathogens

Microbes as Biofertilizers

Biofertilizers are the organisms that enrich the nutrient quality of the soil. Their main sources are bacteria, fungi and cyanobacteria (algae)

Name of the microorganisms	Uses
Rhizobium bacteria	Fix atmospheric nitrogen into organic forms which are used by the leguminous plants
Azospirillum and Azotobacter (free living bacteria)	Fix atmospheric nitrogen
Fungi form symbiotic associations with plants (mycorrhiza)	Absorbs phosphorus from soil and provides to the plant
Cyanobacteria-  Anabaena, Nostoc, Oscillatoria (autotrophic microbes)	fix atmospheric nitrogen
cyanobacteria	Used in paddy fields as it is an important fertilizer that increases soil fertility

FAQs on Microbes in Human Welfare

Q1: Why are fruit juices brought from the market clearer as compared to those which are made at home?

Answer:

This is because of the action of Pectinases and proteases enzymes used to clarify juices (tetra-packs).

Q2: What are anaerobic sludge digesters?

Answer:

In secondary/biological treatment some amount of activated sludge (inoculum) is pumped back into the aeration tank. These are anaerobic sludge digesters.

Q3: Write the importance of microbes in household products.

Answer:

• Lactic acid bacteria/ LAB (Lactic Acid Bacteria) are used for the curdling of milk.
• Baker’s yeast (Saccharomyces cerevisiae) is used to ferment various foods.
• They are puffed and give a net-like appearance because of the production of carbon dioxide gas (the end product of fermentation)