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Microbes
Microbes In Household Products
Microbes In Industrial Products
Microbes In Sewage Treatment
Microbes In Production Of Biogas
Microbes As Biocontrol Agents
Microbes As Biofertilisers
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1. Microbes are microscopic organisms (invisible to
naked eye)
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2. They are present everywhere on earth- in soil, water,
air, in our bodies, plants and even at the most extreme
locations such as hot water geysers and poles.
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3. Microbes are diverse, they can be- protozoa,
bacteria, fungi, viruses, viroids, prions etc.
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4. Microbes are thought to be the main disease causing
agents, but they can be helpful to human beings in
many ways. We will see how in subsequent slides.
Escherichia coli
Lactobacillus
Methanobactarium
Azatobacter
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1. Production of curd from milk
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a. Microbes such as Lactobacillus and a group called Lactic
Acid Bacteria(LAB) convert milk to curd by producing acids
which partially digest and coagulate milk proteins.
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b. A small amount of curd (starter or inoculum) which is
added to milk contains millions of bacteria which multiply
under suitable conditions and thus converting it to curd.
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c. This process increases the nutritional value of milk by
increasing vitamin B12 , it also checks disease causing
organisms in our stomach.
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2. Fermentation
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a. The fermentation of dough is due to bacteria and its
puffed appearance is due to the production of CO2
during fermentation.
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b. Toddy, an alcoholic drink is made from Fermentation
of palm sap.
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c. A yeast, Saccharomyces cerevisiae (baker's yeast) is
used for fermenting bread dough.
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d. Cheese is also a product of fermentation and/or
ripening, and different varieties of cheese are due
to different microbes used for fermenting.
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e. The holes in cheese are due to large CO2 production
by the bacteria.
Saccharomyces cerevisiae
as seen under DIC (Differential
Interference Contrast)
microscope.
The large holes in Swiss cheese
are due to huge amount of CO2
released during fermentation by
Propionibacterium shermanii
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1. Beverages
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2. Antibiotics
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3. Organic acids
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4. Enzymes
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5. Bio-active molecules
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1. Beverages
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a. When juices and malted cereals are fermented they get
converted to ethanol.
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b. Brewer's yeast (Saccharomyces cerevisiae) is commonly
used for fermentation.
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c. Drinks with versatile colour and flavour are produced
depending upon the raw material and nature of processing
used
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d. Classification of beverages
 (i) Whisky, Rum and Brandy are distilled beverages.
 (ii) Wine and beer are not distilled.
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2. Antibiotics
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a.The term means 'against life' with reference to disease
causing organisms.
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b.
The
first
antibiotic
penicillin
was
discovered
by
Alexander Fleming.
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c. Penicillin is obtained from a fungus Penicillium notatum.
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d. These are used in treatment of a number of diseases such
as, diptheria, leprosy, whooping cough, plague etc.
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3. Organic acids
a. Various organic acids are produced with the help of
microbes. The below lists the organic acids and name of
the microbe employed in producing itOrganic Acids
Microbe
1. Citric Acid
1. Aspergillus niger (fungus)
2. Acetic Acid
2. Acetobacter aceti (bacterium)
3. Butyric acid
3. Clostridium butylicum (bacterium)
4. Lactic Acid
4. Lactobacillus (bacterium)
5. Ethanol
5. Saccharomyces cerevisie (yeast)
4. Enzymes produced with the help of microbes arei.Lipases (lipid dissolving, produced by Candida
lipolytica)
 ii. Proteases
 iii. Pectinase
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 a. Lipases are added in detergents for removing oily stains
 b. Pectinases and proteases are used to clear fruit juices
during bottling.
 c. Streptokinase is produced by Streptococcus. It
is
modified by genetic engineering and used as 'clot buster‘
for dissolving blood clots of patients after myocardial
infarction.
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5. Bioactive molecules
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a. Cyclosporin A
 i. A fungus Trichoderma Polysporum produces it.
 ii. It has immuno suppresive properties so it is used as an immuno-
supressive agent during organ transplantation.
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b. Statins
 i. These are the products of fermentation activity of yeast,
Monascus purpureus.
 ii. It inhibits cholesterol synthesis, so used for
lowering blood cholesterol level.
Beer, a
product of
fermentation
Antibiotics
Acetic
acid, the
main
component
of Vineger
Cholesterol lowering
tablets(statins)
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Need for sewage treatment-
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1. The municipal waste water(sewage) contains large amount
of organic waste and microbes.
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2. This can invite diseases and epidemic when this water
meets community water bodies like lake pond and rivers.
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3. To check this the sewage is made less polluting by passing it
through sewage treatment plants(STPs)
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This involves two steps i. Primary Treatment
 ii. Secondary Treatment
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1. Primary treatment
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a. It is a physical process, it uses sedimentation and
filtration to filter small and large particles.
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b. First the sewage is passed through mesh screens of
small pore sizes to remove floating objects like
polythene.
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c. The grit is removed by sedimentation by passing
sewage into grit chamber.
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d. Then it is kept in settling tanks, where the suspended
materials settle down to form the primary sludge.
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e. The remaining fluid is taken for secondary treatment.
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2. Secondary treatment
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a. It is a biological process by heterotrophic bacteria present in the sewage.
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b. The primary effluent is aerated in aeration tanks.
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c. This causes rapid growth of aerobic bacteria, which then as 'flocs'
consume the organic matter to reduce the Biochemical Oxygen
Demand (BOD).
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d. After this the effluent is passed to settling tanks where these 'flocs' get
sedimented. (Activated Sludge).
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e. A part of this sludge is pumped back to aeration tanks for further use.
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f. This sludge is pumped to anaerobic sludge digesters, where anaerobic
bacteria form gases like methane CO2 and H2S.
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g. After this the effluent is released into water bodies like streams and rivers.
Microorganisms In Sewage Treatment
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1. Biogas
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a. Biogas consists of methane(60%) and CO2(40%)
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b. Produced by Methanobacterium by acting on
cellulosic compounds, these are found in rumen of
cattle and anaerobic sludge of sewage.
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c. Cattle dung contains both cellulosic as well as
methanogens so it's used for biogas production.
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d. It is a popular method for meeting energy
requirements of rural households, and also helps in
reducing precious firewood.
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2. The steps involved in the production of biogas-
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a. The biogas plant consists of a 10-15 feet deep
concrete tank in which the slurry of dung is fed.
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b. A floating cover is kept over the slurry which keeps on
rising as the gas is produced in the tank by microbial
activity.
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c. An outlet connected to a pipe is present in the
biogas plant for the removal of biogas and supplying it
to required places.
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d. The spent slurry is removed through another outlet
which can be used as a fertiliser.
A typical biogas plant.
A biogas plant in Tamil Nadu.
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1. Biological control is defined as the reduction of pest
populations by natural enemies and typically involves
an active human role.
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2. For Example-
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a. The spores of Bacillus thuringiensis (Bt) are toxic to
certain larvae, but not harmful for others.
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b. The fungus trichoderma is being used for fighting
plant diseases.
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c. Baculoviruses are the pathogens used for attacking
harmful insects and arthropods, they belong to genus
Nucleopolyhedrovirus.
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1. The use of biofertilsers instead of chemical ones has been
known to keep the soils fertility intact for longer durations. They
are organisms like bacteria, fungi and cyanobacteria, that
enrich the soil.
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2. a. Bacteria - Rhizobium, Azospirilium, Azatobacter fix
atmospheric nitrogen and enrich nitrogen content of soil.
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b. Fungi -They form symbiotic relation with roots of plants eg.
mycorrhiza. It absorbs phosphorous and passes it to plant, also
it shows resistance to pathogens and salinity.
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c. Cyanobacteria - They are autotrophic microbes which can
fix atmospheric nitrogen, for eg. Anabaena, Nostoc,
Oscillatoria. They are important biofertilisers in paddy fileds.