Enhancement of food

11.1 Improvement in Food Production

Food: Organic, energy-rich, edible and nourishing substance that provides energy and keeps the body healthy.

Green plants prepare their own food through photosynthesis.

Animals, including humans, depend directly or indirectly on plants for food.

Food production needs improvement due to:

Rapid increase in world population.

Food scarcity caused by famine

Increasing demand for nutritious food.

Methods to Improve Food Production

Plant breeding

Animal breeding

Both help increase food production in terms of quantity and quality.

11.2 Plant Breeding

Plant breeding: Purposeful manipulation and improvement of the hereditary characters of crop plants to develop new, superior varieties.

It is an applied branch of Botany, combining art and science.

Based on principles of genetics, taxonomy, physiology, pathology, agriculture and recombinant DNA (rDNA) technology.

Objectives of Plant Breeding

1. Increase crop yield.

2. Improve nutritional and overall quality.

3. Increase tolerance to environmental stresses.

4. Develop resistance against pathogens (disease-causing organisms).

5. Increase resistance to insect pests.

Green Revolution

A series of scientific developments that increased food production and helped fight hunger.

Major contributing factors:

● High-quality, high-yielding seeds.

● Use of chemical fertilisers and pesticides.

● Multiple cropping system (growing more than one crop on the same land in a year).

●Modern agricultural machinery.

● Proper irrigation facilities.

● Developed high-yielding and disease-resistant varieties of wheat, rice and maize.

History of Plant Breeding

Plant breeding dates back approximately 10,000 years.

Present-day crops developed through domestication (bringing wild plants under cultivation) and acclimatisation (adaptation to new environmental conditions).

Important Scientists in Green Revolution

1. Dr. Norman E. Borlaug

American biologist; known as Father of the Green Revolution AKA  Agriculture's Greatest Spokesperson.

The Man Who Saved a Billion Lives.

Received Nobel Peace Prize in 1970 for his contribution to the Green Revolution.

Helped save millions of lives from famine in India, Mexico and the Middle East.

2. Dr. M. S. Swaminathan

● Known as Father of Green Revolution in India.

● Introduced and developed high-yielding wheat varieties in India.

● Promoted sustainable agriculture, food security and biodiversity conservation.

● Pioneer of mutation breeding in India.

● Wheat varieties: Sonora, NP 165 and Sharbati.

A. Hybridization and Its Technique

Hybridization: Crossing two genetically different plants to combine desirable characters in their offspring.

Helps: 

● Combine desirable traits of different varieties.

● Produce new genetic combinations and variations.

● Exploit hybrid vigour (heterosis) – superior performance of hybrids over their parents.

Types of Hybridization

1. Intravarietal: Between plants of the same variety.

2. Intervarietal: Between two varieties of the same species.

3. Interspecific: Between two species of the same genus.

4. Intergeneric: Between two genera of the same family.

Interspecific and intergeneric crosses are called wide/distant crosses and rarely occur naturally.

Steps in Plant Breeding (Hybridization)

1. Collection of Variability

Collect wild relatives and cultivated varieties having desirable traits.

Germplasm collection: Collection of genetic variations (different alleles) of a crop.

Conservation methods:

In-situ: Conservation in natural habitats (forests and natural reserves).

Ex-situ: Conservation outside natural habitats (botanical gardens and seed banks).

2. Evaluation and Selection of Parents

Screen germplasm to identify plants with desirable characters.

Select two healthy, vigorous parents with complementary traits.

Self-pollinate for 3–4 generations to obtain pure/homozygous lines.

3. Hybridization

Select:

Female/recurrent parent: Has maximum desirable characters.

Male/donor parent: Provides the missing desirable character.

Collect pollen from male parent and dust it over the stigma of the emasculated female flower 

Fertilisation produces seeds representing the hybrid generation.

F₁ progeny is evaluated for desirable combinations.

4. Selection and Testing of Superior Recombinants

Select superior F₁ hybrids showing hybrid vigour.

Self them for several generations to obtain homozygous, uniform lines.

This prevents further segregation (separation of characters in later generations).

5. Testing, Release and Commercialisation

Evaluate selected lines for Productivity and quality.

Disease and pest resistance.

Initially test under controlled conditions.

Then grow for at least 3 generations in natural fields across different agroclimatic zones.

Best-performing variety is released for farmers.

Green Revolution in India

Since 1961, hybrid varieties, fertilisers, pesticides and proper irrigation helped increase agricultural production.

Major crops: rice, wheat, sugarcane and millets.

1. Wheat and Rice

● During the 1960s, wheat and rice production increased greatly.

● Norman Borlaug developed semi-dwarf wheat varieties.

● Indian wheat varieties: Sonalika and Kalyan Sona.

Semi-dwarf rice varieties were obtained from:

● IR-8: International Rice Research Institute.

● Taichung Native-1: Taiwan.

● Improved Indian rice varieties: Jaya, Padma and Ratna.

2. Sugarcane

● Saccharum barberi – North Indian variety.

● S. officinarum – South Indian variety.

● Thicker stem and high sugar content.

● Does not grow well in North India.

● Both were crossed to combine desirable characters.

● Improved varieties: CO-419, CO-421 and CO-453.

● Developed at Coimbatore, Tamil Nadu.

3. Millets

Improved hybrid varieties:

Maize – Ganga-3.

Jowar – CO-12.

Bajra – Niphad.

These varieties show high yield and water-stress resistance.

11.2 Plant Breeding 

A. Breeding for Disease Resistance

Objective: Develop an inherent ability in plants to prevent pathogens from causing diseases.

Such varieties are called disease-resistant plants.

Technique used: Same as the normal hybridization process.

B. Mutation Breeding

Mutation: Sudden, heritable change in the genetic material (genotype).

It may occur naturally or be induced artificially using chemicals or radiation.

Mutagens: Agents that cause mutations.

Types of Mutagens

1. Physical mutagens:

High temperature, High concentration of CO₂, X-rays, UV rays

2. Chemical mutagens:

Nitrous acid, EMS (Ethyl Methyl Sulphonate)

Mustard gas, Colchicine

Technique:

Seeds or seedlings are exposed to mutagens such as:

Cobalt-60 (Co-60)

UV lamps

X-ray machines

Mutagens cause:

● Gene mutations

● Chromosomal aberrations (structural changes in chromosomes)

● Treated plants are screened for desirable traits like disease/pest resistance and high yield.

Examples:

Jagannath – Rice variety.

NP 836 – Rust-resistant wheat.

Indore-2 – Bollworm-resistant cotton.

Regina-II – Bacterial rot-resistant cabbage.

C. Plant Breeding for Insect-Pest Resistance

● Insects are herbivores and cause heavy losses in crop quantity and quality.

● Resistance can be developed through:

1. Morphological Characters (Physical features):

● Hairy leaves in cotton → Resistance against jassids.

● Hairy leaves in wheat → Resistance against cereal leaf beetle.

● Solid stem in wheat → Resistance against stem borers.

2. Biochemical Characters (Chemical composition):

Maize with: High aspartic acid, Low nitrogen and sugar content.

These characteristics provide resistance against stem borers.

3. Other Plant Characters:

Nectar-less cotton with smooth leaves → Resistance against bollworms.

11.3 Tissue Culture

Tissue culture: Technique in which isolated plant cells, tissues or organs are grown in vitro (outside the organism) on a nutrient medium.

Performed under aseptic conditions (free from contamination) with controlled light, humidity and temperature.

It is an important technique of plant biotechnology.

Explant: Plant part used to initiate tissue culture.

Principle – Totipotency

Totipotency: Inherent ability of a living plant cell to divide, grow and develop into a complete plant.

Gottlieb Haberlandt (1902): First proposed the concept of in-vitro cell culture and plant morphogenesis.

Tissue Culture Medium Contains:

Essential minerals.

Carbohydrates, proteins and fats.

Water.

Growth hormones.

Vitamins.

Agar (solidifying agent used in callus culture).

Most commonly used medium: MS medium (Murashige and Skoog medium).

Types of Tissue Culture

A. Based on nature of explant:

1. Cell culture.

2. Organ culture.

3. Embryo culture.

B. Based on type of in-vitro growth:

1. Callus culture – Solid medium.

2. Suspension culture – Liquid medium.

Maintenance of Aseptic Conditions

● Aseptic conditions prevent contamination by harmful microorganisms.

● Sterilization methods:

● Glassware: Detergents and hot-air oven.

● Nutrient medium: Autoclaving at 15 lb/sq inch pressure for 20 minutes.

● Explant: Treatment with 20% ethyl alcohol and 0.1% HgCl₂.

● Inoculation chamber: Laminar air flow; UV radiation for 1 hour before inoculation.

Other conditions:

Temperature: 18–20°C.

pH of nutrient medium: 5–5.8.

Aeration: Particularly important in suspension culture.

Callus Culture

Uses solid nutrient medium.

Tissue organisation and development are lost.

Explant cells divide repeatedly to form an undifferentiated mass called callus.

Callus can develop into:

Roots → Rhizogenesis.

Shoots → Caulogenesis.

Roots and shoots together develop into a plantlet.

Shaker/agitator is not required.

7. Suspension Culture

Uses single cells or small groups of cells as explants.

Grown in a liquid nutrient medium.

Medium is continuously agitated using a shaker/agitator.

Ensures constant mixing of the medium and explant.

8. Micropropagation (Clonal Propagation)

Commercial method of producing many plants through tissue culture.

Organogenesis via shoots is one of the most widely used methods of plant regeneration.

Produces genetically identical plants called clones.

Examples of commercially produced plants:

Ornamental plants: Orchids, Chrysanthemum, Eucalyptus.

Fruit plants: Banana, Grapes, Citrus.

Advantages of Micropropagation

1. Rapid multiplication: Produces plants quickly.

2. Space-saving: Large number of plantlets produced in a small area.

3. Year-round production: Independent of seasonal conditions.

4. Genetically identical plants: Desired characters (genotype) and sex are maintained for many generations.

5. Conservation: Helps multiply rare and endangered plant species.

6. Development of new varieties: Somatic hybrids help obtain new varieties in a shorter time.

11.4 Single Cell Protein (SCP)

1. Need for SCP

By 2050, the world may need 1,250 million tonnes of meat and dairy products annually.

● Increasing meat and dairy production is not sustainable due to low efficiency of converting animal feed into food.

● Protein malnutrition is common in underdeveloped and developing countries.

● SCP is a non-conventional method of meeting protein requirements.

Its importance was realised during World War I.

Single Cell Protein (SCP): Crude or refined edible protein obtained from pure microbial cultures or dead/dried microbial biomass.

3. Microorganisms Used for SCP

Fungi: Aspergillus niger, Trichoderma viride

Yeast: Saccharomyces cerevisiae, Candida utilis

Algae: Spirulina spp., Chlorella pyrenoidosa

Bacteria: Methylophilus methylotrophus, Bacillus megaterium

Production of SCP

Microorganisms are grown on inexpensive substrates such as: Agricultural wastes: wood shavings, sawdust, corn cobs. Paraffin and N-alkanes. Sugarcane molasses. Human and animal wastes.

● Microorganisms utilise carbon and nitrogen from these materials and convert them into high-quality proteins.

● SCP is used as a protein supplement in human and animal feed.

Nutritional value:

Rich in proteins, vitamins (especially vitamin B-complex), minerals and fats.

Protein content: 43–85%

Uses:

Fattening of calves and pigs.

Fish breeding.

Poultry and cattle farming.

5. Advantages of SCP

1. Rapid multiplication: Microorganisms multiply quickly and produce large biomass in a short time.

2. High protein content: Contains 43–85% protein.

3. Genetic modification: Microbes can be modified to improve amino acid composition.

4. Waste utilisation: Various agricultural and waste materials can be used as substrates.

5. Pollution reduction: Utilisation of waste materials helps reduce pollutants.

6. Nutritional value: Good source of vitamins, amino acids, minerals and crude fibres.

11.5 Biofortification

● Biofortification: Plant breeding technique used to develop crops with higher nutritional value.

● Increases the levels of vitamins, minerals and fats in crops.

● Nutrients may also be supplemented externally.

● Helps overcome malnutrition.

2. Objectives of Biofortification

1. Improve protein content and quality.

2. Improve oil content and quality.

3. Increase vitamin content.

4. Improve micronutrient content and quality.

3. Methods

Conventional selective breeding.

Recombinant DNA technology (r-DNA technology).

Main focus: Improving the nutritional quality of plant foods during their growth and development.

4. Examples of Biofortification

Maize: Fortified maize contains twice the amount of lysine and tryptophan.

Wheat: Atlas 66 – high protein content.

Rice: Iron-fortified rice contains 5 times more iron than normal rice.

Carrot and spinach: Developed with higher vitamin A and mineral content.

Bitter gourd and tomato: Vitamin C-enriched varieties developed.

11.6 Animal Husbandry

Animal husbandry: Agricultural practice of breeding, raising and caring for livestock.

It is both a science and an art.

2. Scope of Animal Husbandry

Deals with breeding and care of useful animals such as: Buffaloes, cows, pigs, horses, sheep, camels and goats.

Also includes:

Poultry farming.

Fish farming.

Beekeeping.

Sericulture (silk production).

Lac culture.

Animal products: Milk, eggs, meat, wool, honey and silk.

3. Need for Scientific Animal Husbandry: 

● India and China together have approximately 70% of the world's livestock population.

● However, their productivity contributes only about 25% of the world's farm produce  

● Merely taking care of animals is insufficient for maximum production.

● Professional management and modern technology are needed to improve quality and productivity.

Management of Farms and Farm Animals

Farm management includes:

Selection of high-yielding breeds.

Proper food and nutritional supply.

Clean environment.

Maintenance of animal health.

Management procedures include:

Veterinary supervision.

Vaccination.

Development of high-yielding crossbreeds.

Production and preservation of animal products.

Distribution and marketing.

A. Animal Breeding

Animal breeding: Controlled reproduction of animals to improve desirable qualities and increase their yield.

Objectives:

Increase milk production.

Improve quality of meat and other products.

Increase egg production.

Develop improved breeds.

2. Breed

A group of animals related by descent and similar in appearance, features, size and body structure is called a breed.

3. Types of Animal Breeding

a. Inbreeding

Breeding between closely related individuals for 4–6 generations.

Increases homozygosity (similar alleles).

Helps to obtain pure lines.

Eliminate harmful recessive genes.

Accumulate superior genes.

Demerit: Reduces fertility and productivity.

b. Outbreeding

Breeding between unrelated animals.

Animals may belong to the same breed but should have no common ancestors for 4–6 generations.

Types of outbreeding:

1. Outcrossing

Mating between unrelated animals of the same breed.

Helps overcome inbreeding depression (reduced fertility and productivity due to inbreeding).

2. Crossbreeding

Superior male of one breed × superior female of another breed.

Develops new breeds with desirable characters.

Example: Hisardale sheep

Bikaneri ewe × Marino ram Developed in Punjab.

3. Interspecific Hybridization

Breeding between two different but related species.

Combines desirable characters of both parents.

Not always successful.

Example: Mule = Horse × Donkey.

Artificial Insemination

● Semen from selected superior males is collected and preserved in frozen condition or introduced into the female reproductive tract.

● Used for controlled breeding.

Advantages:

● Overcomes difficulties in natural mating.

● Avoids inconvenience of transporting animals.

● Allows the use of semen from superior males.

 Multiple Ovulation Embryo Transfer (MOET)

Definition: Technique used to produce several embryos from a superior female animal and transfer them into surrogate mothers.

Steps:

1. Cow is administered an FSH-like hormone to stimulate follicular maturation.

2. Superovulation is induced.

3. About 6–8 eggs mature simultaneously in one cycle.

4. Cow is mated with an elite bull or artificially inseminated.

5. Embryos at the 8–32 cell stage are collected non-surgically.

6. Embryos are transferred into surrogate mothers.

Used in: Cattle, sheep, rabbits and buffaloes.

Importance:

Helps produce superior animals in a short time.

Increases herd size rapidly.

B. Dairy Farm Management

Dairy farming involves the production, processing and distribution of milk and milk products.

Milk yield mainly depends on the quality of animal breeds.

2. Selection of Dairy Animals

Good dairy breeds should have:

High milk-producing capacity.

Adaptability to local climatic conditions.

Disease resistance.

Cow breeds:

Indian breeds: Sahiwal, Sindhi, Gir.

Exotic breeds: Jersey, Brown Swiss, Holstein.

Buffalo breeds found in India: . Jaffarabadi, Mehsana, Murrah, Nagpuri, Nili, Surati

3. Feeding and Care

Provide fodder of proper quality and quantity in suitable proportions.

Silage: Preserved green fodder made from legumes, grasses, maize and jowar.

Silage is supplemented with:

Oil cakes, Minerals, Vitamins, Salts.

4. Cleanliness and Hygiene

● Maintain cleanliness of animals and handlers during milking.

● Ensure hygiene during milk storage and transportation.

● Mechanisation reduces direct contact with milk.

● Animal sheds should be: Cleaned daily.

Spacious, Properly equipped for feeding, watering and lighting.

5. Milk Processing and Marketing

Milk is processed into:

Curd, Cream, Butter, Ghee, Condensed milk, Khoa, Cheese.

6. Additional Income from Dairy Farms

Cow dung → Manure,  Fuel cakes, Gobar gas (used for cooking and lighting).

C. Poultry Farm Management

Poultry: Rearing of birds like chickens, ducks, turkeys and fowls for eggs and meat.

Allied activities: Processing and marketing of eggs/meat, poultry feed, equipment and medicines.

Requirements: Disease-free breeds, proper housing, feed, water, hygiene and healthcare.

Poultry Breeds (Based on Origin)

American: Plymouth Rock, New Hampshire, Rhode Island Red.

Asiatic: Brahma, Cochin, Langshan.

Mediterranean: Leghorn, Minorca.

English: Australorp.

Indian: Chittagong, Aseel, Brahma, Kadaknath.

Important:

Leghorn → Best layer (egg production)

Plymouth Rock, Rhode Island Red, Aseel, Brahma, Kadaknath → Broilers (meat production).

Management

Layers: High-yielding breeds, ventilation, feed, debeaking, lighting, water, sanitation, culling and vaccination.

Broilers: Proper breed, housing, temperature, ventilation, lighting, floor space and feed.

Poultry Diseases

Viral: Ranikhet, Bronchitis, Avian influenza (Bird flu).

Bacterial: Pullorum, Cholera, Typhoid, TB, CRD, Enteritis.

Fungal: Aspergillosis, Favus, Thrush.

Parasitic: Lice, roundworm, caecal worm.

Protozoan: Coccidiosis.

D. Apiculture (Bee Keeping)

Artificial rearing of honey bees to obtain honey, wax, pollen, bee venom, propolis (bee glue) and royal jelly.

Also provides pollination services to crops.

Ancient cottage industry; honey is nutritious and used in traditional medicine.

Honey Bees Found in India

Apis dorsata – Rock/wild bee.

Apis florea – Little bee.

Apis mellifera – European bee

Apis indica – Indian bee.

Requirements and Management

Suitable areas: Places with wild shrubs, fruit orchards and cultivated crops.

Equipment: Hive boxes, comb foundation sheets, bee veil, smoker, gloves, bee brush, uncapping knife, swarm net and queen excluder.

Proper location, swarm collection, seasonal hive management and honey collection are essential.

Regularly inspect hive cleanliness, queen activity, brood condition and water supply.

Importance in Pollination:

Honey bees increase crop productivity in sunflower, mustard, safflower, chilli, cabbage, cucumber, legumes, apple, mango and citrus.

E. Fishery

Fishery: Branch of applied biology dealing with catching, processing, farming and marketing of fish and other aquatic animals.

Examples: Prawns, lobsters, oysters, mussels and crabs.

Types of Fishery

1. Inland Fishery

Fish production from freshwater bodies: ponds, lakes, dams and rivers.

Common fishes:

Labeo rohita – Rohu.

Catla – Catla.

Cirrhina mrigala – Mrigala.

Other carps.

2. Marine Fishery

Capture of fish from seawater.

Indian coastline: Approximately 7,500 km.

Examples:

Harpadon – Bombay duck.

Sardinella – Sardine.

Rastrelliger – Mackerel.

Stromateus – Pomfret.

3. Estuarine Fishery

Capture of fish from estuaries.

Example: Sunderban, West Bengal.

Fish Farm Management

Suitable site and pond excavation.

Hatchery, nursery, rearing and stocking tanks.

Proper water supply, manure and supplementary feed. 

Types of Culture Fishery:

Monoculture: Rearing one fish species.

Polyculture: Rearing multiple fish species.

Fish Preservation

Chilling, freezing, freeze-drying, sun-drying, smoke-drying, salting and canning.

Fishery By-products

Fish oil, fish meal, fertilisers, fish guano, fish glue and isinglass.

Used in paints, soaps, oils and medicines.

Provides employment and self-employment opportunities.

F. Sericulture

Sericulture: Branch of applied Zoology dealing with silkworm rearing and silk production.

Requires less investment and small space.

Provides employment to many families.

Types of Silk

Mulberry silk: Best quality; produced by Bombyx mori.

Tussar silk and Eri silk: Comparatively inferior quality.

Silk quality and quantity depend on the quality of mulberry leaves eaten by larvae.

Management

Requires continuous care and skilled labour.

Silkworm larvae may suffer from protozoan, viral and fungal infections.

Ants, crows, birds and other predators must be prevented from attacking larvae.

G. Lac Culture

Lac: Resinous substance secreted by female lac insect, Tachardia lacca.

Insect feeds on succulent twigs of ber, peepal, palas, kusum and babool.

Pink resin secreted by dermal glands hardens on exposure to air.

Important Points

Lac contains resin, sugar, water, minerals and alkaline substances.

Shellac: Pure form of lac obtained by washing and filtering.

India contributes approximately 85% of world's lac production.

Artificial inoculation on host plants helps obtain regular and better-quality lac.

Uses: Bangles, toys, woodwork, inks and mirrors.

11.7 Microbes in Human Welfare

Biotechnology 

Application of scientific and engineering principles to process materials using biological agents for human welfare.

Microorganisms include algae, fungi, bacteria, viruses, protozoans and nematodes.

Used in food, health, agriculture, medicine, industry, biocontrol and waste utilisation.

Development of Biotechnology

Traditional biotechnology: Up to 1970; based mainly on fermentation.

Modern biotechnology: After 1970.

1. Microbes in Food Preparation

Dosa, Idli and Dhokla

Fermented products made using rice and black gram.

Bacteria: Leuconostoc and Streptococcus.

CO₂ produced during fermentation causes the dough to puff up.

2. Microbes as a Source of Food

Microbes are rich in proteins and vitamins.

SCP includes dead and dried microbial cells such as bacteria, algae, moulds and yeasts.

Mushrooms and truffles are edible higher fungi.

Their fruiting bodies are rich in proteins, vitamins, minerals and amino acids.

Low in calories, sugar and fat.

3. Dairy Products

Lactic Acid Bacteria (LAB): Lactobacillus converts lactose (milk sugar) into lactic acid.

Lactic acid coagulates milk and partially digests casein (milk protein).

Used in preparing curd, yoghurt and cheese.

i. Curd

Prepared using Lactobacillus acidophilus.

Helps prevent the growth of disease-causing microbes.

ii. Yoghurt

Prepared using:

Streptococcus thermophilus.

Lactobacillus bulgaricus.

iii. Buttermilk

Acidulated liquid left after churning butter from curd.

iv. Cheese

Prepared by coagulating milk using LAB.

Curd is filtered to separate whey.

Solid mass is ripened using moulds to develop flavour.

Important Cheese Microbes:

Roquefort cheese → Penicillium roquefortii.

Camembert cheese → Penicillium camembertii.

Swiss cheese → Propionibacterium shermanii produces CO₂, forming large holes.

11.8 Role of Microbes in Industrial Production

Microbes are used in industrial fermentation to produce: Alcoholic beverages , Organic acids , Vitamins , Growth hormones , Enzymes , Antibiotics

Fermenters

Large vessels used to grow microorganisms on an industrial scale.

Main function: Provide a controlled environment for microbial growth to obtain the desired product.

Production of Alcoholic Beverages

Beverages: Liquids prepared for drinking, e.g. tea, coffee, beer and wine.

Alcoholic beverages are produced by alcoholic fermentation of specific substrates.

Use of microbes in beverage production dates back to the Vedic period (5000–7000 BC).

Microorganism used:

Yeast: Saccharomyces cerevisiae var. ellipsoideus (Brewer's yeast).

Ferments malted cereals and fruit juices to produce ethanol.

Types of Alcoholic Beverages:

Without distillation: Wine and Beer.

With distillation: Whiskey, Brandy and Rum.

Tubular tower fermenter: Used for large-scale alcohol production.

Traditional Examples:

Palm wine → Fermented sugar sap of palm/coconut.

Fenny (Goa) → Fermented fleshy pedicels of cashew fruits

B. Production of Organic Acids

Microbes are used for commercial production of organic acids.

Important Organic Acids and Microbes:✨️

Citric acid → Aspergillus niger.

Gluconic acid → Aspergillus niger.

Fumaric acid → Rhizopus arrhizus.

Acetic acid (vinegar) → Acetobacter aceti.

Uses:

Citric acid → Confectionery.

Fumaric acid → Resins and wetting agents.

Gluconic acid → Medicine; improves solubility of Ca²⁺.

C. Production of Vitamins

● Vitamins are complex organic compounds required in small amounts for normal body functions.

● Humans cannot synthesise most vitamins hence, they must be obtained through diet.

● Microbes are used for commercial production of vitamins.

● Examples : Thiamine (B₁), Riboflavin (B₂), Pyridoxine (B₆), Folic acid, Pantothenic acid, Biotin, Vitamin B₁₂, Ascorbic acid (Vitamin C), Beta-carotene (Provitamin A), Ergosterol (Provitamin D).

Important Vitamins and Microbial Sources:

Vitamin B₂:

Neurospora gossypii

Eremothecium ashbyi

Vitamin B₁₂: Pseudomonas denitrificans.

Vitamin C: Aspergillus niger.

D. Production of Antibiotics

Antibiotics: Secondary metabolites produced by microbes that inhibit the growth of other pathogens.

Produced by bacteria, fungi and some algae.

Used to treat diseases like plague, whooping cough, diphtheria and leprosy.

E. Production of Enzymes

Enzymes: Protein biocatalysts that speed up biochemical reactions.

Microbes produce enzymes commercially.

Important Enzymes & Sources:

Invertase → Saccharomyces cerevisiae

Pectinase → Sclerotinia libertine, Aspergillus niger

Lipase → Candida lipolytica

Cellulase → Trichoderma koningii

Uses:

Textile, paper, food and detergent industries.

Lipase → Removes oil stains.

Streptokinase → Clot buster (helps dissolve blood clots).

F. Gibberellin Production

Gibberellins: Plant growth hormones that promote stem elongation.

First isolated by Yabuta and Sumiki (1938) from fungus-infected rice seedlings (Gibberella fujikuroi).

About 15 types of gibberellins have been isolated.

Applications:

● Induce parthenocarpy (fruit formation without fertilisation) in apple and pear.

● Break seed dormancy.

● Induce flowering in long-day plants (LDP).

● Increase grape fruit size.

Extra Important Facts

Streptokinase: Produced by Streptococcus; used as a clot buster.

Statins: Produced by yeast Monascus purpureus; lower blood cholesterol by inhibiting cholesterol synthesis.

11.9 Microbes in Sewage Treatment

1. Sewage

Sewage is wastewater carried through drainage systems.

● It is a municipal waste containing:

Human excreta and household waste.

Dissolved organic matter.

Pathogenic microorganisms (disease-causing microbes).

Industrial, hospital and slaughterhouse waste.

Industrial sewage may contain toxic organic and inorganic chemicals.

Pathogens present in sewage:

Bacteria, viruses, protozoans, nematodes and microfungi.

May cause diseases like dysentery, cholera, typhoid, polio and infectious hepatitis.

During sewage decomposition:

Initially, aerobic and facultative anaerobic microorganisms predominate.

Later, strict anaerobic microorganisms, especially methanogenic bacteria, become active.

They produce methane (CH₄) and carbon dioxide (CO₂).

2. Composition of Sewage

Water: 99.5–99.9%

Organic and inorganic matter: 0.1–0.5% (suspended and dissolved).

Composition varies according to the source of wastewater.

Examples: Textile, chemical, pharmaceutical, dairy, tannery and oil-refinery industries.

3. Microorganisms in Sewage

● Sewage contains bacteria, viruses, fungi, protozoa, nematodes and algae.

● Their number and types vary according to sewage composition.

● Raw sewage may contain millions of bacteria per ml.

Important bacteria:

Coliforms

Faecal Streptococci

Anaerobic spore-forming bacilli

4. Sewage Treatment

Before wastewater is released into natural water bodies or made available for reuse, it must be treated to remove: Organic matter, Inorganic salts, Pathogenic microorganisms

Sewage treatment involves four basic steps:

1. Preliminary Treatment

Includes two processes:

i. Screening

Sewage is passed through screens or nets.

Removes large suspended and floating materials.

Examples: Plastic, rags and other solid waste.

Prevents obstruction during further treatment.

ii. Grit Chamber

Screened sewage is passed through grit chambers.

Coarse particles settle down due to gravity.

Removes sand, pebbles and other heavy particles.

2. Primary Treatment (Physical Treatment)

Sewage is passed into a primary sedimentation tank.

Suspended solids and organic matter settle down.

About 50–70% of suspended solids are removed.

Coliform organisms are reduced by about 30–40%.

Primary Sludge:

Organic matter settled at the bottom of the tank.

Removed mechanically.

Supernatant (Effluent):

Liquid remaining above the settled sludge.

Still contains dissolved organic matter and microorganisms.

Sent for secondary treatment.

3. Secondary Treatment (Biological Treatment)

Primary effluent is passed into large aeration tanks.

Air is continuously pumped and sewage is mechanically agitated.

Aerobic bacteria multiply rapidly and form flocs.

Flocs:

Mesh-like masses of bacteria held together by slime and fungal hyphae.

Role of Flocs:

Aerobic microbes consume most of the organic matter.

This reduces the BOD (Biochemical Oxygen Demand) of wastewater significantly.

BOD:

Amount of dissolved oxygen required by microorganisms to decompose organic matter in water.

Higher BOD indicates greater organic pollution.

Lower BOD indicates reduced organic pollution.

4. Tertiary Treatment

After BOD reduction, wastewater is passed into a settling tank.

Bacterial flocs settle down and form activated sludge.

Activated Sludge:

Settled bacterial flocs obtained after secondary treatment.

A small portion is returned to the aeration tank as an inoculum (source of microorganisms).

The remaining sludge is transferred to anaerobic sludge digesters.

Anaerobic Sludge Digestion:

Anaerobic bacteria digest bacteria and fungi present in the sludge.

Gases produced include:

Methane (CH₄)

Carbon dioxide (CO₂)

Hydrogen sulphide (H₂S)

Final Treatment:

Treated effluent is chlorinated to kill pathogenic bacteria.

It is then released into natural water bodies like rivers and streams.

Digested sludge is disposed of appropriately.

11.10 Microbes in Energy Generation

Biogas is a renewable, non-conventional source of energy produced by microbial fermentation under anaerobic conditions.

Used as domestic and industrial fuel.

Common raw materials include plant waste, animal waste, agricultural waste, domestic waste and municipal waste.

Cattle dung is the most commonly used substrate for biogas production.

Composition of Biogas:

Methane (CH₄): 50–60%

Carbon dioxide (CO₂): 30–40%

Hydrogen sulphide (H₂S): 0–3%

Other gases: CO, N₂ and H₂ (traces).

Biogas is highly inflammable and burns as a fuel.

2. Biogas Plant

Common models: KVIC and IARI.

The digester used for biogas production is called a biogas plant.

Main Parts:

1. Digester: Underground tank made of concrete, bricks, cement or steel where anaerobic digestion occurs.

2. Gas Holder: Cylindrical gas tank above the digester that collects the produced biogas.

3. Charge Pit: Side opening through which raw material (cow dung slurry) is fed into the digester.

3. Biogas Production

Anaerobic digestion occurs in three main stages:

i. Hydrolysis (Solubilization)

● Cattle dung is mixed with water in equal proportion to form slurry.

● Slurry is fed into the digester.

● Anaerobic hydrolytic bacteria break down complex organic substances into simpler molecules.

Examples:

Carbohydrates → Simple sugars

Proteins → Amino acids

Lipids → Fatty acids

Microorganisms: Clostridium and Pseudomonas.

ii. Acidogenesis

Facultative anaerobic acidogenic bacteria and obligate anaerobes convert simple organic substances into:

Organic acids (formic acid and acetic acid)

Hydrogen (H₂)

Carbon dioxide (CO₂)

iii. Methanogenesis

● Final stage of biogas production.

Methanogenic bacteria convert acetate, hydrogen and carbon dioxide into methane and other products.

Examples: Methanobacterium and Methanococcus.

Important Reactions:

1. Acetic acid: 12CH₃COOH → 12CH₄ + 12CO₂

2. Formic acid: 4HCOOH → CH₄ + 3CO₂ + 2H₂O

3. Carbon dioxide reduction: CO₂ + 4H₂ → CH₄ + 2H₂O

4. Benefits of Biogas

1. Cheap, safe and renewable source of energy.

2. Can be used for domestic cooking, lighting, street lighting and small-scale industries.

3. Burns with a blue flame without producing smoke.

4. Improves sanitation by utilizing organic wastes.

5. Eco-friendly and helps reduce environmental pollution.

6. Leftover digested sludge can be used as manure/fertilizer.

11.11 Role of Microbes as Biocontrol Agents

1. Biocontrol

● Biocontrol is the use of natural biological methods to control pests and diseases.

● Natural enemies like bacteria, fungi, viruses and protozoans are used as biocontrol agents.

● They control pests by causing diseases, competing with or killing them.

● Reduces dependence on harmful chemical pesticides and insecticides.

2. Examples of Microbial Biocontrol

i. Bacillus thuringiensis (Bt)

● Used to control butterfly caterpillars.

● Bt spores are sprayed on plants and eaten by insect larvae.

● In the larval gut, Cry protein toxin is released, which kills the larvae.

ii. Trichoderma species

● Free-living fungi found in the rhizosphere (root region).

● Control soil-borne fungal plant pathogens.

● Produce substances like viridin, gliotoxin and gliovirin that inhibit pathogens causing root and rhizome rot.

3. Microbial Pesticides and Their Hosts

Bacteria:

Bacillus thuringiensis → Caterpillars, cabbage worms.

B. papilliae and B. lentimorbus → Beetles.

Fungi:

Beauveria bassiana

Entomophthora

Zoophthora radicans

Control aphids, mealybugs, mites and whiteflies.

Protozoans:

Nosema lacustae → Grasshoppers, caterpillars and crickets.

Viruses:

Nucleopolyhedrovirus (NPV) and Granulovirus (GV) → Caterpillars, gypsy moths, ants, wasps and beetles.

4. Bioherbicides

● Weeds are unwanted plants that compete with crops for water, minerals, light, air and space.

● They may also act as collateral hosts for pathogens.

● Microorganisms and certain insects are used to control weeds naturally.

Microbial Herbicides and Their Hosts

A. Pathogenic fungi (Mycoherbicides):

Phytophthora palmivora → Milkweed.

Alternaria crassa → Water hyacinth.

Fusarium spp. → Various weeds.

B. Bacterial pathogens:

Pseudomonas spp.

Xanthomonas spp.

Agrobacterium spp.

Attack several weeds.

C. Insects as herbicides:

Tyrea moth → Senecio jacobaea.

Cactoblastis cactorum → Cactus weeds.

11.12 Role of Microbes as Biofertilizers

1. Biofertilizers

● Fertilizers provide essential nutrients required for plant growth.

● Chemical fertilizers contain mineral salts of NPK (Nitrogen, Phosphorus and Potassium).

● Excessive use of chemical fertilizers causes soil, air and groundwater pollution and may increase soil acidity.

● Organic fertilizers include FYM (Farm Yard Manure), compost and green manure.

Biofertilizers 

● Commercial preparations of living microorganisms (bacteria, cyanobacteria and fungi).

● Applied to plants, soil or composting pits to improve soil fertility.

● Mostly include nitrogen-fixing microorganisms.

● Eco-friendly, cost-effective and help maintain long-term soil fertility.

2. Types of Biofertilizers

1. Nitrogen-fixing Biofertilizers

● Convert atmospheric nitrogen (N₂) into usable nitrogenous compounds through ammonia.

● Nitrogen-fixing microorganisms are called diazotrophs.

Two types:

● Symbiotic: Rhizobium, Anabaena, Frankia.

● Live in association with plants, generally in their roots.

● Free-living (Non-symbiotic): Azotobacter, Nostoc, Clostridium, Beijerinckia, Klebsiella.

2. Phosphate-solubilizing Biofertilizers

● Convert insoluble phosphates (e.g. rock phosphate) into soluble forms available to plants.

● Examples: Pseudomonas striata, Bacillus polymyxa, Agrobacterium, Micrococcus, Aspergillus.

3. Compost-making Biofertilizers

● Microorganisms decompose organic waste into compost or humus.

● Include bacteria, fungi, actinobacteria, protozoa and rotifers.

4. Cyanobacteria as Biofertilizers

● Photosynthetic, nitrogen-fixing microorganisms.

May be free-living or symbiotic.

● Examples: Anabaena, Nostoc, Plectonema, Oscillatoria.

● Anabaena is associated with Azolla and Cycas.

3. Classification of Biofertilizers

A. Bacterial Biofertilizers

Include eubacteria and cyanobacteria.

Based on function:

Nitrogen-fixing

Phosphate-solubilizing

Compost-making

Cyanobacterial biofertilizers are mainly nitrogen-fixing.

B. Fungal Biofertilizers

Include mycorrhizal fungi.

Classified into:

Ectomycorrhizae

Endomycorrhizae

. Fungal Biofertilizers (Mycorrhiza)

● Mycorrhiza is a symbiotic association between fungi and roots of higher plants.

● Discovered by Frank (1885).

Two types:

I. Ectomycorrhizae

● Fungal mycelium forms a mantle around the outer surface of roots.

● Increases absorptive surface area of roots.

● Enhances absorption of water and nutrients (N, P, Ca and K).

● Some hyphae enter root tissues and form Hartig net in intercellular spaces of root cortex.

II. Endomycorrhizae

Fungal hyphae grow between and within root cortical cells.

Form:

● Arbuscules: Finely branched structures inside cells.

● Vesicles: Storage structures, mostly in intercellular spaces.

● Also called Vesicular-Arbuscular Mycorrhizae (VAM) or AM fungi.

● Help plants grow well even in less-irrigated lands.

. Benefits of Mycorrhiza

1. Enhances absorption of P, Zn, Cu, Ca, N, Mn, Br and Fe.

2. Increases water uptake.

3. Promotes plant growth by secreting hormones.

4. Protects plants from harmful microbes by producing antibiotics.

 Important Biofertilizer Microorganisms

1. Rhizobium

● Rod-shaped, motile, aerobic, Gram-negative and non-spore-forming bacteria.

● Contains Nif genes (nitrogen-fixation genes) and nod genes (nodulation genes).

● Forms symbiotic association with roots of leguminous plants.

● Produces root nodules and fixes atmospheric nitrogen.

Examples:

R. leguminosarum → Pea.

R. phaseoli → Beans.

2. Azotobacter

● Free-living, aerobic, nitrogen-fixing and non-photosynthetic bacterium.

● Does not form root nodules.

● Used for non-leguminous crops like rice, cotton and vegetables.

3. Azospirillum

● Free-living, aerobic, nitrogen-fixing bacterium.

● Associated with roots of corn, wheat and jowar.

● Fixes about 20–40 kg nitrogen/ha.

● Used for cereals, millets, cotton and oilseeds.

4. Anabaena

● Filamentous, nitrogen-fixing cyanobacterium.

● Contains specialized colourless cells called heterocysts, which are sites of nitrogen fixation.

● Forms associations with Cycas (coralloid roots) and Anthoceros.

5. Azolla

●Free-floating aquatic fern used as a biofertilizer in rice fields.

● Contains Anabaena filaments in the aerenchyma of its dorsal leaf lobe.

● Anabaena fixes atmospheric nitrogen.

. Benefits of Biofertilizers

1. Low-cost and suitable for marginal farmers.

2. Eco-friendly and pollution-free.

3. Increase soil fertility.

4. Blue-green algae (BGA) produce growth-promoting substances, organic acids, proteins and vitamins.

5. Azotobacter supplies nitrogen and antibiotics to soil.

6. Improve soil texture, structure, pH and water-holding capacity.