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 Antibiotics have greatly improved our capacity to treat deadly diseases such as plague, whooping
cough. Diphtheria and leprosy.
Chemicals, Enzymes and other Bioactive Molecules:
 Aspegillus niger (a fungus) produces citric acid.
 Acetobacter aceti (a bacterium) produce acetic acid.
 Clostridium butylicum (a bacterium) produce butyric acid.

 Lactobacillus(a bacterium) produces lactic acid.
 Saccharomyces cerevisiae (yeast) used for production of ethanol.
 Lipases are used in detergent produced by microbes.
 Pectinase, proteases and cellulase, make bottled fruit juices clearer.
 Streptokinase produced by Streptococcus used as a ‘clot buster’, for removing clots from the
blood vessels.
 Cyclosporin-A produced by a fungus called Trichoderma polysporum used
as immunosuppressive agent in organ transplantation.
 Statins produced by Monascus purpureus used as blood cholesterol lowering agents. It acts as
competitive inhibitor for the enzyme responsible for synthesis of cholesterol.
MICROBES IN SEWAGE TREATMENT:
 The waste water generated in cities and town containing human excreta. This municipal water-
water is called sewage.
 Before disposal to the natural body sewage is treated in sewage treatment plants (STPs) to make it
less polluting.
 Treatment is done by heterotrophic microbes naturally present in sewage.
Primary treatment:

 Involves the physical removal of particles – large and small from sewage through filtration and
sedimentation.
 Initially floating debris is removed by sequential filtration.
 The grit (soil and small pebbles) are removed by sedimentation.
 All solids that settle form the primary sludge, and the supernatant forms the effluents.
 The effluents are from the primary settling tank taken for secondary treatment.
Secondary treatment or Biological treatment:
 The primary effluent is passed into large aeration tanks.
 This allows vigorous growth of useful aerobic microbes into flocs.

 The growth of microbes consumes the major part of the organic matter in the effluent. This significantly
reduces the BOD (biochemical oxygen demand) of the effluent.
 BOD refers to the amount of oxygen required to oxidize total organic matter by bacteria, present in one liter
of water.
 BOD is the measures of the organic matter present in the water.
 Greater the BOD of the waste water more is its polluting potential.