NEET Biology Microbes in Human Welfare Notes

Microbes such as bacteria, fungi, protozoa and viruses are used in households, industry, sewage treatment, biogas production, pest control and agriculture. This NEET Biology notes page on Microbes in Human Welfare covers curd, yoghurt, cheese, toddy, fermented beverages, antibiotics, organic acids, enzymes, statins, sewage treatment, biogas plants, biocontrol agents and biofertilizers, with check point questions and answers.

While going through the chapter pay special attention to the following -

Terms -
1. Inoculum 2. Toddy 3. Arrack
4. Statin 5. Sludge 6. Flocs

Tables -
1. Types of antibiotics with their source and action.

- Microbes, also known as micro-organisms (like protozoa, bacteria, fungi, plant viruses, viroids and prisons) can be observed under microscopes. Microbe is a minute life form which have a size of less than 0.1 mm.
- Microbes are present everywhere - in soil, water, air, inside our bodies and that of other animals and plants. They are present even at sites where no other life form could possibly exist-sites, deep in the soil, under the layers of snow several meters thick and in highly acidic environment.
- Microbes can be grown on culture nutritive media to form colonies which are used for mass production of certain desirable products and for scientific study of metabolism, genetics and structure of micro-organism.
- During their metabolism, microbes produces chemicals, some of which have been in use by human beings since ages. Microbes can be modified genetically to produce many type of chemicals. Therefore, microbes are ideal for biotechnology.

MICROBES IN HOUSEHOLD PRODUCTS

- Humans share a close relationship with a surprising variety of microscopic organism.

Microbes play an important role in the preparation of household products & industrial products valuable to human beings.

Microbes in food prepossessing products

- LAB is lactic acid bacteria which produce acids that coagulates and partially digest the milk proteins. Milk is changed into curd, yoghurt & cheese etc.
- Asmall amount of curd act as inoculum in fresh milk. Inoculum actually contains millions of lactic acid bacteria.
- Lactic acid bacteria causes coagulation of milk protein casein. They also improve the nutritional quality of curd by increasing vitamin B₁₂.

[Figure: At a Glance chart - Microbes in human welfare: Microbes in household products (Microbes in food processing: Curd, Yogurt, Bread Milk, Cheese, Toddy, Single cell protein (SCP), Dough, Soyabean preparation, Kefir); Microbes in industrial products (Fermented beverages, Yeast, Production of antibiotics, Chemicals, Enzymes and other bioactive molecules: Organic acid, Alcohol, Enzyme, Cyclosporin A, Statin, Vitamins); Microbes in Sewage Treatment; Microbes in Production of Biogas; Microbes as Biocontrol agent; Microbes as Biofertilizers]

Examples -
- Lactobacillus lacti : Milk fermentation.
- Lactobacillus acidophilus : Cheese production.
- Streptococcus thermophilus or Lactobacillus bulgaricus : Yoghurt production.
- Saccharomyces cerevisiae : Bread production.
- S. lactis, L. bulgaricus : Kefir production.
- Lactose fermenting yeast : Butter milk production.
- In stomach, LAB plays an important role in checking disease causing microbes.

Curd

- Curd is prepared from both skimmed and cream milk by inoculating the same with LAB.

Milk is boiled and cooled to temperature of slightly less than 40°C. It is mixed with a small quantity of inoculum or curd. The latter contains Lactobacillus acidophilus.
- Curd also possesses antimutagenic and anticancer biochemicals. The bacterium produces Lactase which converts milk sugar lactose into lactic acid.

Yogurt

- Yogurt is a preserved milk product having a distinct taste and a thick texture than milk. Milk is heated to 80° - 90°C for half an hour. It is cooled to 40° - 43°C and mixed with inoculum containing Streptococcus thermophilus and Lactobacillus burlgaricus. After four hours yoghurt is ready.

Bread Milk

- It is an acidulated product, which is formed by inoculating skimmed milk with starter culture of Streptococcus cremoris, Streptococcus lactis and Leuconostoc species.
- Acidulated liquid left after churning of butter from curd is also called buttermilk.

Cheese

- Cheese is one of the oldest food items in which microbes were used. Different varieties of cheese were known by their characteristic texture, flavour and taste, E.g. swiss cheese and roquefort cheese.
- Swiss cheese have large holes due to production of large amount of CO₂ by a bacterium - Propionibacterium sharmanii.
- The Roquefort cheese are ripened by growing a specific fungi on them, which gives them a particular flavour.
- Cheese is prepared by coagulation of casein and other minor milk proteins (curdling of milk) by enzyme rennin extracted from calf gastric mucosa. Streptococcus and Lactobacillus species are involved in the manufacture of most cheese.

Toddy

- Toddy, a traditional drink in India is fermented sap of palm by Baker’s yeast, Saccharomyces cerevisiae.
- The term toddy is also applied to sweet exudation got by tapping unopened spadix of coconut. Palm sugar and jaggery is produced by boiling it. The exudation is rich in natural yeasts which bring about its rapid fermentation to produce an intoxicating alcoholic drink. Arrack is obtained b Arrack y distillation of fermented toddy.

Dough

- Dough used for making foods like dose, idli, is also fermented by bacteria. The puffed-up appearance of dough to due to production of CO₂ gas.

Soyabean Preparation

- Soy sauce is a flavoured salted brown sauce that is obtained from soyabean fermented with the help of Aspergillus oryzae, Lactobacillus, Saccharomyces rouxii and Torulopsis species.
- Soju and Tofu are cheese like products of soyabean obtained after fermentation of Nucor species.
- Tempeh is Indonesian food formed by fermenting, drying, salting and frying of soyabean.

Kefir

- It is a fermented milk where a mixture of lactic acid bacteria (e.g. Lactobacillus Kefir) and yeast (e.g. Candida kefir) are used as kefir grains.
- Kefir contains small quantity of ethanol, carbon dioxide, acetaldehyde & deacetyl.

MICROBES IN INDUSTRIAL PRODUCTS

- Industrial production requires the formation of large quantities of the product, which normally involves the microbial reactions to proceed in a specialized vessel called or bioreactor.
- Beverages and antibiotics are some examples.

Fermented beverages

- Manufacture of fermented beverages especially alcoholic drinks like wine, beer, whisky, brandy, gin, rum etc.
- Whisky, Brandy, Rum are distilled product of fermented broth whereas wine and beer are non-distilled.
- Manufacture of fermented beverages especially alcoholic drink in the brewing industry is based on the alcoholic fermentation of malted cereals & fruit juices in presence of brewers yeast (Saccharomyces cerevisiae).

Yeast

- Yeast (Saccharomyces cerevisiae) is the most important and most extensively used micro-organisms in biotechnology.Yeast cells are used in the manufacture of bread and also a source of food, vitamins and other growth factors. There are two types of yeasts - baker’s yeast and alcohol yeast.
- Bakers yeast is grown on molasses and sold as a food flavouring agent.
- Alcohol yeast is used by brewing industry for the production of different types of alcoholic beverages depending upon the medium and fermenting agent.
- Desirable characters of S. cerevisiae (Baker’s yeast) to be selected for commercial production of baker’s yeast are :
(i) Ability to ferment sugar in dough vigorously and rapidly.
(ii) Selective stability of strain selected as quality of product depends on strain of yeast-used.
- Yeast fermentation of molasses is used for production of ethyl alcohol and the alcohol fermentation by acetic acid, bacteria leads to acetic acid production.

Acetic acid formation:
2CH₃CH₂OH + 2O₂ → 2CH₃COOH + 2H₂O

- There are two types of fermentation process - batch fermentation (or closed system) and continuous process (or open system).
- Downstream processing is the name given to the stage after fermentation when desired product is recovered and purified.

Production of antibiotics

- Antibiotics are chemical substances which are produced by some microbes and can kill or retard growth of other disease causing microbes.
- Penicillin was the first antibiotic to be discovered.
- Alexander Fleming while working on Staphylococci plates observed that in one of unwashed culture plate, it could not grow because of chemical produced by mould Penicillium notatum grown on it which produces chemical penicillin.
- Antibiotics have been extensively used for treatment of certain epidemic disease like cough, diphtheria, leprosy, plague, etc.
- Florey and Chain demonstrated remarkable chemotherapeutic effectiveness of penicillin during 1939 - 41.
- Fleming, Chain & Florey were awarded the Nobel prize in 1945 for the discovery of penicillin & its use.
- An antibiotic that act on a variety of pathogenic organism is called a broad spectrum antibiotic. Specific antibiotic is effective only against one type of pathogens.
- Antibiotics functions either as bactericides (killing bacteria) or bacteriostatic (inhibiting growth of bacteria).

Table 10.1 : Types of antibiotics with their source and action

Connecting Concepts
- Waksman and woodruff isolated actinomycin in 1941 and streptothricin in 1942.
- Waksman & Albert (1943) and Waksman (1944) discovered streptomycin.
- Burkholder (1947) isolated chloromycetin.

Chemicals, Enzymes and other bioactive molecules

- Organic acids, alcohols and enzymes are industrially produced by the use of microbes.

Organic acid

- Citric acid is produced on an industrial scale by fermentation of crude sugar solutions of molasses with Aspergillus niger (a fungus).
- Acetobacter aceti (a bacterium) produces acetic acid.
- Butyric acid is prepared by the fermentation of sugar or starch with Clostridium butylicum (a bacterium).
- Lactic acid fermentation is performed by Lactobacillus bacteria.
- Gallic acid is obtained with the help of Aspergillus niger. It is employed in ink making.
- Gluconic acid is manufactured with the help of Penicillium purpurogenum and P. Chrysogerium. It is used in pharmaceuticals. Calcium gluconate is used as a source of calcium in feeding infants and pregnant woman and for treatment of milk fever in high producing dairy cows.

Alcohols

- Ethanol, also called ethyl alcohol, is the alcohol found in alcoholic beverages. It is produced by fermenting sugars with yeast (Saccharomyces cerevisiae).

Enzymes

- Some important enzymes produced industrially by microbes are -
- Amylase, which attacks starch, is used in the manufacture of beer, bread and textiles. It is obtained from Aspergillus oryzae, A.niger, Rhizopus oryzae etc.
- Lipase is used in detergent formulation to remove oily stains.
- Streptokinase is also called tissue plasminogen activator or TPA. It is produced by bacterium Streptococcus, is used as clot buster for removing blood clot in patients suffering from myocardial infractions.
- Pectinases are obtained from fungi grown on pectin containing media, e.g. Aspergillus niger, Bysschlamys fulvo. Pectinases are used in enhancing juice extraction from fruits, clearing of fruit juice, removing bitterness, and fermentation of green coffee.
- Proteases are obtained from both bacteria (e.g. Bacillus subtilis, B. licheniformis) and fungi (e.g. Aspergillus oryzae, Penicillium roquefortii). They are used in enhancing tenderness of meat, extraction of fish liver oil, softening of cheese and bread and in detergents for removing protein based stains.

Cyclosporin A

- CyclosporinA, a bioactive immunosuppressive agent is used in organ transplant patient, produced by Trichoderma polysporum.

Statin

- Statin is blood cholesterol lowering agent produced by yeast Monascus and it acts by competitively inhibiting enzyme (HMG CoAreductase of liver) responsible for cholesterol synthesis. Statin lower LDL cholesterol level.

Vitamins

- Most of the vitamins are made commercially by chemical synthesis.
- Vitamin C was the first vitamin to be produced by a fermentation process using Acetobacter, a wild bacterium.
- Bacteria used for industrial production of Vitamin B₁₂ are Propionibacterium shermanni, P. frendenreichii and Pseudomonas denitrificans.

Nutrient medium is made of starch corn syrup, corn sugar and molasses. The cells are harvested & autolysed to separate the vitamin.
- Vitamin B2 (Riboflavin) is synthesized by many micro-organisms including bacteria, yeast & fungi. The fungus, Ashbya gossypii is used for the microbial production of vitamin B2.

MICROBES IN SEWAGE TREATMENT

- Sewage is the waste & waste water produced by residential & commercial sources & discharged into sewers.
- Wastewater treatment is necessary before wastewater is disposed off without producing any undesirable or harmful effect.
- Disposal of inadequately treated wastewater leads to-
(i) Greater possibility of dissemination of pathogenic micro-organism.
(ii) Accumulation and dissemination of toxic chemicals that endanger ecosystems and threaten public health.
(iii) Contamination of oyster and shellfish, making them unsafe for human consumption.
(iv) Depletion of O₂ of water by unstable organic matter in sewage, killing aquatic life.
(v) Creation of miscellaneous objectionable conditions such as offensive odour and debris, making property less expensive.
- Wastewater treatment process are carried out by municipal treatment plant as a community process. These are primary treatment & secondary treatment.
- Primary (1°) Treatment : It is a physical process that involves physical removal of particles from the sewage through filtration and sedimentation. So, it remove coarse solids and settleable solids in sedimentation units (tanks, basin, or mechanical devices) by which particulate material is concentrated as sludge. The sludge and liquid effluent are processed separately. The effluent from the primary settling tank is taken to secondary.
- Secondary (2°) treatment : Secondary treatment involves the oxidation of organic material in effluent by microbial method. These are -
(i) Activated sludge process.
(ii) Filteration by intermittent sand filters and trickling filter.
- The liquid sludge is sprayed over surface of bed of crushed stone, gravel, slag which saturate the liquid with oxygen. This maintains aerobic conditions in the bed. The filtering medium of tank is coated with a microbial flora - the zoological film - consisting of bacteria, fungi, protozoa and algae.As the sewage sweep over them, the micro-organism metabolize organic constituents to more stable end product. This requires repetition over a few weeks.

[Figure: Fig. 10.1 Flow chart of sewage treatment - Sewage passes through Comminute and Grit removal and Primary Settling (Primary treatment, physical), giving Sludge to the Sludge Digester (Biogas; Manure, Burning, Land Filling) and effluent to Aeration Tanks or Trickling Filter (Secondary treatment, biological), then Secondary Settling, then Liquid released to the River; Compost and Landfilling are alternate paths]

- In activated sludge process, aeration of sewage in large aeration and agitation tank, lead to the formation of flocs (masses of bacteria associated with fungal filaments to form mesh like structure) and floccules. When they are vigorously aerated, flocculation occurs and this contain large number of actively metabolizing bacteria, yeast, mould and protozoa.

This growth is effective in oxidation of organic compound. This significantly reduces BOD (Biological chemical oxygen demand). BOD is measure of organic content in H₂O.

Greater is BOD in H₂O, more is its polluting potential.
- Anaerobic sludge digester : Solid which accumulates during sedimentation are pumped into sludge digester. This sludge is digested with the help of anaerobic and facultative bacteria. These micro-organisms bring about a decrease in organic solid by degrading them to soluble substances and gaseous products which has 60-70% methane and 20-30% CO₂.

This gas mixture is used as biogas for heating purpose and for operating power.
- The remains of aerobic digester is removed to mechanical drying unit. The sludge dries into cakes which are incinerated, reduced to ash and used as landfill.
- Composting is decomposition of dewatered sludge by thermophilic bacteria under forced aeration. Effective period of time is 21 days after which it transforms into humus type material and is suitable for use as a soil conditioner.
- Ganga Action Plan and Yamuna Action Plan are a part of this strategy of sewage treatment.

MICROBES IN PRODUCTION OF BIOGAS

- Biogas is a gaseous fuel, produced by methanogens, which are anaerobic bacteria growing on cellulosic material and produce large amount of methane alongwith CO₂ and H2. e.g., Methanococcus, Methanobacterium.
- Biogas is also called swamp gas, landfill gas and marsh gas depending on where it is produced.
- The production of biogas results in the formation of a stabilized residue that acts as the fertilizer.
- Biogas can be easily stored to provide more efficient source of energy which has wider uses than the traditional energy sources.
- Biogas plant work is based on the process called anaerobic digestion or fermentation of organic matter including manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock under anaerobic conditions.
- Dung can be used for generation of biogas, commonly called gobar gas.
- A biogas plant has a large concrete or brick lined airtight cylindrical tank called digester. It has a charge pit for passage of slurry into digester, a floating gas holder of metal with an outlet for gas and a pit for removal of sludge or manure. The biogas thus produced is used for cooking & lighting.

[Figure: Fig. 10.2 A typical biogas plant - Dung and Water enter the Digester, Sludge is removed, and Gas (CH₄ + CO₂ + ...) collects in the floating Gas-holder]

- Biogas contains 50-70% methane, 30-40% CO₂, traces of hydrogen, hydrogen sulphide and nitrogen.
- Stages in anaerobic digestion during biogas formation are -
- The facultative anaerobic micro-organisms breakdown the polymers into soluble monomers with the help of enzymatic hydrolysis. Lignin cannot be broken down by micro-organism, so it remains as residue along with inorganic salts.
- The monomers become the substrate for micro-organisms. These are then converted into organic acids.
- In this stage, soluble organic acids (acetic acid) are formed for the substrates of the last stage.
- Finally, methanogenic anaerobic bacteria produce methane (biogas).
- Biogas can be easily stored to provide more efficient source of energy which has wider uses from the traditional energy source.
- The production of biogas results in the formation of a stabilized residue that acts as a fertilizers.
- Biogas is also called gobar gas because excreta of cattle has methane released by methanogens.
- Technology of biogas production was developed in India mainly by IARI (Indian Agricultural Research Institute) and KVIC (Khadi and Village Industries Commission).
- Oil spill is cleaned by genetically engineered species of Pseudomonas poteta so that it has the capacity to metabolize four major hydrocarbons of petroleum - camphor, octane, xylene and nepthalene.

MICROBES AS BIOCONTROL AGENT

- The latest trend in control is to minimise use of poisonous chemicals and achieve better result through integrated method involving combination of biological, cultural and control methods.
- Use of predators, animal composite, micro-organisms such as bacteria/virus to control insect pest, pathogen and weed is called biological control and biological agents are called biocontrol agents.
- Bioherbicides are living organisms, which control the weeds. First bioherbicide was developed in 1961 and it was a mycoherbicide derived from a fungus Phytophthora palmivora which control the growth of milkweeds vines in citrus orchards.
- Another example of biological control of weed is the control of overgrowth of lacti by introduction of cochineal insect (Cactoblastis cactorum) in India and Australia.
- Lady bird and Dragonfly are useful to get rid of aphids and mosquitoes respectively.
- Bt Cotton is genetically modified cotton having Bacillus thuringiensis genes. Bacterium Bacillus thuringiensis (Bt) is used as microbial control agent in order to control butterfly caterpillars. It is sprayed on plants like Brassica and fruit trees which are attacked by insect larvae. In the gut of larvae, Bt release toxin and insect larvae are killed. It is killing only caterpillars, leaving all other insects unharmed.
- Bt cotton has B. thuringiensis toxin genes and such plants are resistant to attack by insect pest.
- Trichoderma species are free living fungi that are common in root ecosystem. They are effective biocontrol agents of several plant pathogen.
- Baculoviruses, belongs to genus Nucleopolyhedrovirus, are pathogenic virus which infect & kill many insects pests and other arthopod pests. These are for species specific, narrow spectrums insecticidal application.
- Advantages of biocontrol organism
- Specific, narrow spectrum application.
- No negative impact on plants, mammals, birds, fish and insect.
- Beneficial insects are conserved to aid in an overall integrated pest management [IPM] programme, where an ecologically sensitive area is being treated.

Connecting Concepts
- Methanogens are archae that produce methane as a metabolic byproduct. These bacteria are comm-only found in the anaerobic sludge during sewage treatment. These bacteria are also present in rumen (a part of stomach) of cattle. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.

MICROBES AS BIOFERTILIZERS

- Biofertilizers are organisms that enrich nutrient quality of soil. The main source is bacteria, fungi and cyanobacterium.
- Examples :
1. Rhizobium species in root nodules of leguminous plant.
2. Azospirillium and Azotobacter are free living species in soil.
3. Fungi :

Fungi :

Fungi Gleomus is symbiotically associated with plant where fungal symbiont absorb phosphorus from soil and passes to plants. Plants inturn show better resistance to root borne pathogens, tolerance to salinity, drought and overall growth of plant.
4. Cyanobacteria such as Anabaena, Nostoc and Oscillatoria (autotrophic microbes) in paddy field.
- These all are marketed as liquid formulations or powder commercially to farmers to replenish soil nutrients and to reduce dependence on chemical fertilizers.
- Organic farming is use of biofertilizers, biocontrol agents and biologically produced compost.
- Use of biofertilizers -
(i) To increase fertility of soils. Some free living or symbiotic bacteria and blue green algae fix gaseous nitrogen as ammonia & release it increasing the fertility of soil.
(ii) They are the most advanced biotechnology tool necessary to support sustainable agriculture.
(iii) They are having low cost input & they do not pollute the environment. They also reduce the dependence on chemical fertilizers.

CHECK POINT QUESTIONS

1. Fill in the blanks :

(i) LAB converts ............................. sugar of milk into ......................

Answer: lactose; lactic acid

Teacher's Note:
a) LAB is lactic acid bacteria, mainly Lactobacillus.

(ii) Large holes in swiss cheese are due to production of large amount of ..................................

Answer: carbon dioxide (CO₂)

Teacher's Note:
a) The bacterium is Propionibacterium sharmanii.

(iii) Arrack is obtained by distillation of fermented ..............................

Answer: toddy

Teacher's Note:
a) Toddy is fermented palm sap.

(iv) Gallic acid is obtained with the help of ........................................

Answer: Aspergillus niger

Teacher's Note:
a) Gallic acid is used in ink making.

(v) Baker's yeast is grown on .......................... and sold as a flavouring agent.

Answer: molasses

Teacher's Note:
a) Baker's yeast is Saccharomyces cerevisiae.

2. Name any two enzymes that are used for clearifying bottled juices.

Answer the question above.

Answer: Pectinases and proteases

Teacher's Note:
a) Pectinases come from fungi such as Aspergillus niger.
b) They also increase juice extraction from fruits.

3. Expand - LAB, TPA.

LAB and TPA

Answer: LAB - Lactic Acid Bacteria; TPA - Tissue Plasminogen Activator

Teacher's Note:
a) TPA is another name for streptokinase.

4. Which enzyme is also called TPA ?

Enzyme called TPA

Answer: Streptokinase

Teacher's Note:
a) It is produced by the bacterium Streptococcus and acts as a clot buster.

5. Write one word for the following:

(i) A small amount of a fungus used to inoculate fresh culture medium.

Answer: Inoculum

Teacher's Note:
a) A little curd added to fresh milk is the common example.

(ii) Immunosuppresent agent in organ transplant patient which is produced by Trichoderma polysporum.

Answer: Cyclosporin A

Teacher's Note:
a) It prevents rejection of the transplanted organ.

1. Expand - BOD, GAP, IARI, KVIC

BOD, GAP, IARI, KVIC

Answer: BOD - Biological Oxygen Demand; GAP - Ganga Action Plan; IARI - Indian Agricultural Research Institute; KVIC - Khadi and Village Industries Commission

Teacher's Note:
a) BOD measures the organic content of water.
b) Higher BOD means more polluting potential.

2. Which sewage treatment involves activated sludge process and filteration by intermittent sand filters & trickling filter.

Sewage treatment type

Answer: Secondary treatment (biological treatment)

Teacher's Note:
a) Primary treatment is physical.

3. Name two plans as a part of sewage treatment.

Two plans

Answer: Ganga Action Plan and Yamuna Action Plan

Teacher's Note:
a) Both aim to clean river water by treating sewage.

1. Fill in the blanks :

(i) Most important baculovirus involved in biological control is ................................

Answer: Nucleopolyhedrovirus (genus Nucleopolyhedrovirus)

Teacher's Note:
a) It infects and kills insect and other arthropod pests.

(ii) ......................... is an excellent biofertilizer for rice cultivation.

Answer: Cyanobacteria (Anabaena, Nostoc, Oscillatoria)

Teacher's Note:
a) They fix nitrogen in paddy fields.

(iii) ....................refers to symbiotic association between the fungus & the roots of higher plants.

Answer: Mycorrhiza

Teacher's Note:
a) Glomus is a fungus of this type; it absorbs phosphorus from the soil.

(iv) Mycoherbicides, which controls the growth of milkweeds vines in citrus orchards, is derived from .......................................

Answer: Phytophthora palmivora

Teacher's Note:
a) It was the first bioherbicide, developed in 1961.

(v) ........................is a symbiotic bacterium which occurs in the root nodules of legumes.

Answer: Rhizobium

Teacher's Note:
a) Azotobacter and Azospirillum are free living in soil.