1. Milk is converted into curd with the help of bacteria like Lactobacillus acidophilus Lactobacillus lactis and Streptococcus lactis are commonly called Lactic Acid Bacteria (LAB).
2. The LAB bacteria grow in milk and convert it into curd, thereby digesting the milk protein casein.
3. A small amount of curd added to fresh milk as a starter or inoculum contains millions of Lactobacilli, which under suitable temperature \(\left(\leq 40^{\circ} \mathrm{C}\right)\) multiply and convert milk into curd by fermentation.
4. Curd is more nutritious than milk as it contains a number of organic acids and vitamins.

(a) Antibiosis: Property of antibiotics to kill microbes.
(b) Superbugs: Bacterial strains gained resistance against antibiotics.

Broad-spectrum antibiotics act against a wide range of disease-causing bacteria.
Narrow-spectrum antibiotics are active against a selected group of bacterial types.

Erythromycin, Chloromycetin, Neomycin, Kanamycin

Beverages, antibiotics, organic acids, amino acids, vitamins, biofuels, single cell protein, enzymes, steroids; vaccines, pharmaceutical drugs.

(a) The flavor in yogurt is due to acetaldehyde formation.
(b) Large holes in Swiss Cheese is due to more CO₂ production by Propionibacterium shermanii

A fermentor (bioreactor) is a closed vessel with adequate arrangement for aeration, agitation, temperature, pH control, and drain or overflow vent to remove the waste biomass of cultured microorganisms along-with their products.

Curd is more nutritious than milk Since it contains a number of organic acids and vitamins

The use of naturally occurring or genetically engineered microorganisms to reduce or degrade pollutants is called bioremediation. Bioremediation is less expensive and more sustainable than other re-mediations available

Cyanobacteria (or) blue green algae (BGA) are prokaryotic free-living organisms which can fix nitrogen Oscillatoria, Nostoc. In water logged paddy fields  Cyanobacteria multiply and fix molecular nitrogen. Cyanobacteria secrete growth promoting substances like indole-3- acetic acid, indole-3-butyric acid, naphthalene acetic acid, amino acids, proteins, vitamins which promotes plant growth and production.

They are genes present in the bacterium Bacillus thuringiensis and code for crystal proteins called Delta-endotoxin which are toxic to certain Insect pests. The Bacteria is used to produce genetically engineered insect resistant plants.

The use of a microbes or other biological agents to control a specific pest is called a biopesticide. Biopesticides are used to control insect pests. The lady bird beetle and dragonflies are useful to control aphids and mosquito larvae respectively.

Biocontrol is a method of controlling pest by use of microbes such as fungi, bacteria, viruses or by naturally occurring substances derived from plants and animals.
Eg.Lady bird beetle is used to control aphids.

BOD stands for Biological Oxygen Demand. BOD refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. The greater the BOD of the waste water, the more is its polluting potential.

Enzymes - Produced from Yeast (Saccharomyces cerevisiae) and bacteria
(i) Eg: pectinase, protease and cellulase - Bottled juices are clarified.
(ii) Rennet - separate milk into solid curds for cheese making.
(iii) Streptokinase (from Streptococcus) - Clot busier - (removing clots from the blood vessels of patients who have undergone myocardial infarction patients).
Cycloporin 'A' - Immuno suppressant used in organ transplantation (produced from the fungus Trichoderma Polysporum).