By going through these Maharashtra State Board 12th Science Biology Notes Chapter 11 Enhancement of Food Production students can recall all the concepts quickly.
Maharashtra State Board 12th Biology Notes Chapter 11 Enhancement of Food Production
Improvement in Food Production-
- Food: It is defined as any solid or liquid substance, which is swallowed, digested and assimilated in the body to keep us well.
- It is an organic, energy-rich, non-poisonous, edible, and nourishing substance.
- Importance of food: It gives us energy for all body activities. It keeps us alive, strong and healthy.
1. Plant breeding involves the improvement or purposeful manipulation in the heredity of crops and the production of new superior varieties of crops.
2. It involves genetic alteration of plants to increase their value and utility.
3. Objectives of plant breeding : Some objectives of plant breeding are common (as given below) and some vary according to type and use of the plant.
- To increase crop yield.
- To improve quality of produce.
- To increase tolerance to environmental stresses.
- To develop varieties of plants resistant to pathogens and insect pest.
- To alter the lifespan.
4. Different methods of plant breeding : Introduction, selection, hybridization, mutation breeding, polyploidy breeding, tissue culture, r-DNA technology, SCP (Single cell protein).
5. The present day crops are the result of domestication and acclimatization.
A. Hybridization and its technique :
- Hybridization is an effective means of combining the desirable characters of two or more varieties.
- New genetic combinations can be created by hybridization.
- It exploits and utilizes hybrid-vigour.
4. Types of Hybridization :
- Intravarietal (between plants of same variety)
- Intervarietal (between two varieties of the same species)
- Interspecific (between two species of the same genus)
- Intergeneric (between two genera of the same family)
- Wide/distant crosses : Crosses between distantly related parental plants. Interspecific and intergeneric hybrids are rare to occur in the nature.
5. The main steps of the plant breeding program (Hybridization) :
(1) Collection of variability :
- Germplasm collection : The entire collection having all the diverse alleles (i.e. variations) of all genes in a given crop.
- Germplasm conservation :
- In situ conservation : Done with the help of forests and Natural Reserves.
- Ex situ conservation : Done through botanical gardens, seed banks, etc.
(2) Evaluation and selection of parents
(4) Selection and testing of superior recombinants
(5) Testing, release and commercialization of new cultivars
6. Green revolution :
- Green revolution is the development of high- yielding improved varieties of wheat and rice through techniques of plant breeding, in the decade from 1961, which helped the farmers to attain record production of agricultural crops in our country.
- Basic elements for Green revolution : The use of seeds of improved varieties of crops for cultivation, expansion of land for cultivation (farm land), optimum use of pesticides and fertilizers, multiple cropping system, modern farm machinery and proper irrigation system.
- Dr. Norman E. Borlaug was awarded the Nobel prize for developing the semi-dwarf varieties of wheat at international centre for wheat and maize.
Steps of hybridization
- Evaluation and selection of parents with different qualities
- Obtaining pure lines by selfing of selected parents for three to four generations
- Identification of parents as male parent (donor) and female parent (recurrent)
- Collection of pollen grains from the flowers of male parent
- Emasculation of flowers of the female parent before anthesis
- Artificial cross (dusting of pollen grains collected from male parent on the stigma of emasculated flowers)
- Bagging, tagging of the emasculated flower of female parent
- Development of fruits and F1 seeds
- Selection and testing of F1 hybrid for combination of desirable characters
- Field trials for yield (productivity)
- Testing and the release of variety
7. Indian Hybrid Crops :
(1) Wheat and Rice :
- Hybrid wheat varieties in India : Sonalika and Kalyan Sona
- Semi-dwarf rice varieties in India : Jaya, Padma and Ratna
- Semi-dwarf rice varieties were developed from IR-8 (International Rice Research Institute) and Taichung native-I (from Taiwan) and introduced in India.
(2) Sugar cane :
- Saccharum barberi : Native of North India and it has poor yield and sugar content.
- S. officinarum : Grown in South India, has thicker stem and high sugar contents, but it does not grow well in North India.
- Hybrid varieties developed by crossing these two species have desirable combinations of characters like high sugar content, thicker stem and the ability to grow in North India.
- Sugar cane varieties developed at Coimbatore, Tamil Nadu : CO-419, 421, 453
(3) Millets : Hybrid maize (Ganga-3), Jowar (CO-12) and Bajra (Niphad) : High yielding and resistant to water stress.
8. Plant Breeding for Disease Resistance :
- Its objective is to develop varieties that are resistant to plant pathogens.
- It is carried out by hybridization process.
- Some of the plant diseases are as follows.
Plant pathogens Diseases Viruses Tobacco mosaic disease Chilli mosaic disease Fungi Brown rust of wheat Late blight of potato Red rot of sugar cane Smut of wheat Bacteria Black rot of crucifers
- Disease resistant varieties of different crops :
Disease resistant varieties Diseases Pusa sadabahar of chilli Chilli mosaic virus, Tobacco mosaic virus and leaf curl Pusa shubhra of cauliflower Black rot and curl blight black rot Himgiri variety of wheat Hill bunt Leaf and stripe rusy Pusa swarnim of Brassica White rust
B. Mutation Breeding :
- Mutation : It is a sudden heritable change in the genotype, caused naturally.
- Natural (physical) mutagens : High temperature, high concentration of C02, X-rays, UV rays.
- Chemical mutagens : Nitrous acid, EMS (Ethyl – Methyl – Sulphonate), Mustard gas, Colchicine, etc.
- Effects of mutagens : Gene mutations and chromosomal aberrations.
- Seedlings or seeds are irradiated by Cobalt 60 or they are exposed to UV bulbs, X-ray machines, etc. The treated seedlings are then screened for resistance to diseases/ pests, high yield, etc.
Mutant varieties :
- Rice : Jagannath
- Wheat : NP 836 (rust resistant)
- Cotton : Indore-2 (resistant to bollworm)
- Cabbage : Regina-II (resistant to bacterial rot), etc.
C. Plant Breeding for Developing a Resistance to Insect Pest :
1. Resistance due to morphological characters :
- Hairy leaves in cotton : Vector resistance from jassids.
- Hairy leaves in wheat : Vector resistance from cereal leaf beetle.
- Solid stem in wheat : Resistance to stem borers.
2. Resistance due to biochemical characters :
- The high aspartic acid and low nitrogen and sugar content in maize : Resistance against stem borers.
- The nectar-less cotton having smooth leaves : Resistance against bollworms.
3. Some pest resistant varieties:
|Insect resistant varieties of various crops||Insect pests|
|Pusa Sawani, Pusa A-4 of Okra (Bhindi)||Fruit and shoot borer|
|Pusa Gaurav of Brassica||Aphids|
|Pusa Sem 2 and Pusa Sem 3 of Flat bean||Jassids, aphids and fruit borers|
1. Tissue culture : It is growing isolated cells, tissues, organs ‘in vitro’ on a solid or liquid nutrient medium, under aseptic, controlled conditions of light, humidity and temperature, for achieving different objectives.
2. Explant : The part of plant used in tissue culture.
3. Totipotency : An inherent ability of living plant cell to grow, divide, redivide and give rise to a whole plant.
4. Haberlandt (1902) : He gave concept of in vitro cell culture (plant morphogenesis).
5. The plant tissue culture medium : It consists of all essential minerals, sources for carbohydrates, proteins and fats, water, growth hormones, vitamins and agar (for callus culture).
6. The most preferred medium for tissue culture : MS (Murashige and Skoog) medium.
7. Types of tissue culture :
- Based on the nature of explant : Cell culture, organ culture and embryo culture.
- Based on the type of in vitro growth : Callus culture (solid medium is used) and Suspension culture (liquid medium is used).
8. Requirements of tissue culture :
(1) Maintenance of aseptic conditions :
- Sterilization of glassware : It is carried out using detergents, hot air oven.
- Sterilization of nutrient medium : It is done by using autoclave.
- Sterilization of explant : It is carried out by treatment of 20% ethyl alcohol and 0.1% HgCl2.
- Sterilization of inoculation chamber (Laminar air flow) : It is carried out by using UV ray tube for 1 hour before performing actual inoculation of explant on the sterilized nutrient medium.
(2) Temperature : 18 °C to 20 °C
(3) pH of nutrient medium : 5 to 5.8
(4) Aeration (particularly for suspension culture)
9. Steps in tissue culture : They are as given in the chart.
- Cleaning and sterilization of glassware and instruments in an autoclave or oven
- Preparation of defined nutrient medium . (MS medium)
- Sterilization of nutritive medium in an autoclave
- (For 20 minutes under constant pressure of 15/lb/inch2)
- Isolation and surface sterilization of explant
- Inoculation of the explant in the culture flask containing sterilized nutrient medium.
(Inoculation is done in the laminar air flow cabinet unit) Incubation of the inoculated explant
(cells of explant divide and give rise to callus, within 2-3 weeks)
- Sub culturing of the callus (Division of callus into 3-4 parts which are transferred to fresh culture medium)
- Organogenesis (Initiation of rooting and shooting)
- Plantlet formation
- Hardening of plantlets (Plantlets are transferred to polythene bags containing sterilized soil and kept at low light and high humid conditions for appropriate time period)
- Hardened plantlets are transferred to field
10. Sub culturing : Both the callus and suspension cultures die in due course of time. Therefore, sub culturing is necessary for continuation of the technique. In this a part of callus or suspension culture is transferred to fresh medium.
11. Micropropagation (Clonal Propagation) :
- It is a type of tissue culture technique by which large number of plants are regenerated using organogenesis.
2. It is used in commercial production of plants like orchids, Chrysanthemum, Eucalyptus, banana, grapes, citrus, etc.
3. Advantages of micropropagation :
- Rapid multiplication of large number of plants within a short period and from a small space.
- Plants are obtained throughout the year, independent of seasons.
- Desirable characters (genotype) and desired sex of superior variety can be maintained for several generations.
- Conservation of rare plant and endangered species.
- Somatic hybrids (cybrids) can be used to develop new variety in short time span.
- High yielding varieties of banana like Shrimati, Basarai and G – 9 are used in Maharashtra.
12. Applications of tissue culture :
- Production of disease free plants and haploid plantlets.
- Production of stress resistant plants, micropropagation.
- Protoplast culture.
- Production of secondary metabolites.
- Culture of rare plants.
- Somaclonal variations.
- Application of tissue culture in forestry, agriculture, horticulture, genetic engineering and physiology.
Single cell protein (SCP)-
1. Conventional method to increase food yield : Use of different methods of crop improvement, biofertilizers, biopesticides, chemical fertilizers and high yielding varieties.
2. Nonconventional methods to increase the
food yield : Use of SCP .
3. , SCP is required to meet growing demand for
protein and to avoid protein malnutrition.
4. Single cell protein : It is a crude or a refined edible protein, extracted from pure microbial cultures or from dead or dried cell biomass.
5. Substrates used for the production of SCP : Wood shavings, sawdust, corn cobs, paraffin, N-alkanes, sugar cane molasses, human and animal wastes.
6. The microorganisms used for the production of SCP :
- Fungi : Aspergillus niger, Trichoderma viride
- Yeast : Saccharomyces cerevisiae, Candida utilis
- Algae : Spirulinaspp, Chlorella pyrenoidosa
- Bacteria : Methylophilusmethylotrophus, Bacillus megasterium
7. Advantages of Single Cell Protein :
- Microbes multiply fast. Hence, a large quantity of biomass can be produced in a short duration.
- The microbes can be easily genetically modified to vary the amino acid composition.
- SCP is a rich source of proteins (43% to 85% WAV basis), vitamins, amino acids, minerals and crude fibres.
- As waste materials are used as a substrate for SCP there is less pollution.
i. e. SCP can be used as fodder for achieving fattening of calves, pigs, in breeding fish, in poultry and cattle farmimg.
1. Biofortification is a method of developing crops for having higher quantity and quality of vitamins, minerals and fats, to overcome problem of malnutrition.
2. Objectives of biofortification :
- Improvement in protein content and quality
- Improvement in oil content and quality
- Improvement in vitamin content
- Improvement in micronutrient content and quality
3. Methods of development of biofortified varieties : Conventional selective – breeding practices and r-DNA technology.
4. Some examples of biofortification :
- Fortified Maize (Twice the amount of amino acids – lysine and tryptophan)
- Wheat – Atlas 66 (High protein content)
- Rice (Has 5 times more iron)
- Carrot and spinach (Enriched with vitamin A and minerals)
- Bittergourd, tomato (Enriched with vitamin C enriched, developed by IARI)
- Animal husbandry-
1. Animal husbandry is an agricultural practice of breeding and raising livestock.
2. It deals with care and breeding of livestock like buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc. which are useful to : humans.
3. Products obtained from animals : Milk, eggs, meat, wool, honey, silk, etc.
4. The production can be increased by –
- Effective management procedures
- New technologies in various farm systems to j improve quality and productivity
- Use of industrial principles of production processing and marketing
5. Management of farms includes selection of high yielding breeds, taking care of food requirements, supply of adequate nutritional sources, cleanliness of the environment and maintenance of health.
6. Management of farm animals includes veterinary supervision, vaccination, high yielding cross breed development, production and preservation of products, distribution and marketing.
A. Animal breeding :
1. Aims of animal breeding :
(1) To increase the yield of animals.
(2) To improve the desirable qualities of the products.
(3) To develop breeds with desirable characters.
2. Breed : A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc.
3. Types of breeding :
(1) Inbreeding : Mating of two closely related individuals within the same breed for 4 to 6 generations.
(2) Outbreeding : Breeding of unrelated animals. It is of following types :
- Outcrossing : Mating of animals within the same breed, but having no common ancestors on either side of mating partners up to 4-6 generations is called outcrossing. [Mote : Outcrossing is not same as interspecific hybridization. ]
- Cross-breeding : Cross-breeding is a practice in which superior males of one breed are mated with superior females of another breed.
- Interspecific hybridization : Mating between male and female animals of two different related species, e.g., interspecific hybridization between horse and donkey produces a mule.
4. Artificial insemination : Used for controlled breeding experiments. Semen from the superior male is collected and injected into the genital tract of the female.
5. Multiple Ovulation Embryo Transfer (MOET) : MOET provides chances of successful production of hybrids.
B. Dairy farm management:
- Dairy industry: It involves production, processing, marketing and distribution of milk and various milk products. Cow dung, manure, fuel cakes and gobar gas (for cooking and lighting) are sources of additional income.
- Breeds of cows :
- Indian breeds of cows : Sahiwal, Sindhi, Gir”
- Exotic breeds of cows : Jersey, Brown Swiss, Holstein.
- Breeds of buffaloes in India : Jaffarabadi, Mehsana, Murrah, Nagpuri, Nlli, Surati.
- Cattle feed : Silage, oilcakes, minerals, vitamins and salts.
- The cattle shed : It must be clean, spacious with adequate facilities for feeding, watering and lighting.
- Cleanliness and hygiene of the cattle and handlers is important during milking, storage and transport of milk and milk products.
- Mechanization of these reduces the chance of direct contact with the product.
- Daily visit of veterinary doctor to dairy farm is mandatory to diagnose health problems, diseases and for their rectification.
C. Poultry farm management:
1. Poultry : It includes chicken, ducks, turkey, and fowls which are domesticated for their eggs and meat.
2. Allied professions to poultry : Processing of eggs and meat, marketing of poultry products, compounding and sale of poultry feed, poultry equipment, pharmaceuticals, feed additives, etc.
3. Requirements for poultry farm Management:
Selection of proper and disease free breed, suitable and safe farm condition, proper feed and water, hygiene and health care.
4. Poultry breeds (On the basis of their origin) :
- American breeds : Plymouth Rock, New Hampshire, Rhode Island Red
- Asiatic breeds : Brahma, Cochin and Langshan
- Mediterranean breeds : Leg horn, Minorca
- English breed : Australorp
- Indian breeds : Chittagong, Aseel, Brahma and Kadaknath.
5. Best layer (for eggs) : Leghorn.
6. Best broilers (for meat) : Plymouth rock, Rhode Island Red, Aseel, Brahma and Kadaknath.
7. Management of layers : It involves purchase of high yielding chicken, well-ventilated farms, proper feed, debeaking, lighting, waterer, sanitation, culling and vaccination.
8. Management of broilers : It involves selection of breed, housing, temperature, ventilation, lighting, floor space and broiler feed.
9. Poultry diseases :
- Viral diseases : Ranikhet, Bronchitis, Avian influenza (bird flu), etc. Bird flu had serious impact on poultry farming and also caused infection to humans.
- Bacterial diseases : Pullorum, Cholera, Typhoid, TB, CRD (chronic respiratory disease), Enteritis, etc.
- Fungal diseases : Aspergillosis, Favus and Thrush.
- Parasitic diseases : Lice infection, round worm, caecal worm infections, etc.
- Protozoan diseases : Coccidiosis.
D. Apiculture or bee keeping :
- Apiculture is artificial rearing of the honey bees.
- Products obtained by apiculture : Honey, wax, pollen, bee venom and royal jelly.
- Honey bees are important pollinators for crop plants and fruit trees.
- Apis dorsata (Rock bee or wild bee), Apis melltfera (European bee), Apis indica (Indian bee), Apis Jlorea (Little bee) are the four commonly occurring species in India.
- Apis mellifera and Apis indica are the : suitable species for apiculture and hence Eire : called domesticated species.
- Equipment required for apiculture: It includes beehive boxes, comb foundation sheets, bee veil, smoker, bee brush, gloves, gumshoes, uncapping knife, swarm net, queen : excluder, overall hive tool, etc.
- Successful apicultures also requires familiarity with the habits of bees, selection of suitable location, catching and hiving of swarms, management of hives during different seasons, handling and collection of honey, bee wax and other products, periodic inspection for cleanliness of hive boxes, activity of bees and queen, condition of brood, provision of water.
- Pollination of variety of crop plants by honey bees increases the productivity of honey and crop.
- Catching, processing, fish farming and marketing of the fish and other edible aquatic organisms is called fishery.
- Some fishes, prawns, lobsters, oysters, mussels, crabs, etc. are commercially important varieties.
- Inland fishery, estuarine fishery and marine fishery are the three main types of fisheries.
- A long coastline of India of about 7500 km and 40 to 50 lakh acres of fresh water bodies together constitute fishery potential.
- Common fresh water fishes, Rohu, Catla, Mrigal, common carp, grass carp, silver carp, etc. while marine fishes such as Hilsa, Bombayduck, sardines, pomphrets, mackerel, etc. are important varieties of fish.
- Fish farming is another occupation related to fishery in which culturing of some varieties of fish is done. Monoculture and polyculture are two main methods of aquaculture.
- Maintenance of fish farm : It involves selection of suitable site, excavation of ponds, requirements of hatchery tank, nursery tank rearing tank, stocking tank or ponds, water source, manures, supplementary feed, etc.
- Fish farming or culturing of commercially important edible fishes is only possible in fresh water bodies.
- Fish spoilage is prevented by preservation methods such as chilling, freezing, freeze drying, sun-drying, salting, canning, etc.
- Fish oil, fish meal, fertilizers, fish guano fish glue and Isinglass are some of the by-products made from the fish.
- Rearing and production of silkworm (Bombyx mori) for obtaining silk is sericulture.
- Types of silk fibres : Mulberry silk, Tussar silk and Eri silk. Best quality mulberry silk is produced by Bombyx mori.
G. Lac culture :
- Tacchardia lacca insect produces lac. Lac is the resinous substance produced by dermal glands of the female insect.
- Plants such as her, peepal, palas, kusum, babool, etc. form the feed of these insects.
- 85% of lac produced in the world is from India.
- Various articles such as bangles, toys, woodwork, polish inks, silvering of mirrors, etc. are produced from lac.
- Artificial inoculation of plants give better and regular supply of lac.
Microbes in human welfare-
1. Biotechnology : It is defined as applications of ‘Scientific and Engineering principles for the processing of materials by biological agents to provide goods and service to humans or for human welfare’.
2. Microbes in food preparation :
- Lactobacilli : Dhokla
- Leuconostoc and Streptococcus bacteria : Dosa and idlis.
- Microbes as the source of food : e.g. SCR fleshy fruiting bodies of edible mushrooms and truffles (higher fungi).
Dairy Products :
- Curd : Lactobacillus acidophilus
- Yoghurt : Streptococcus thermophilus and Lactobacillus bulgaricus
- Buttermilk : It is the acidulated liquid left after churning of butter from curd.
- Cheese : The milk is coagulated with LAB. The curd formed is filtered to separate whey and the solid mass is then ripened with growth of mould that develops flavour in it.
- ‘Roquefort cheese : Ripened by blue- green mold Penicillium roquefortii
- Camembert cheese : Ripened by blue- green mold Penicillium camembertii
- Swiss cheese : Ripened by Propionibacterium shermanii. The large holes in Swiss cheese are developed due to production of a large amount of CO2
Role of Microbes in Industrial Production-
Useful products produced during fermentation : Alcoholic beverages, organic acids, vitamins, growth hormones, enzymes, antibiotics and other molecules of medical significance are produced.
Statins produced by yeast Monascus purpureus are blood cholesterol lowering agents. They are competitive inhibitors of the enzyme that catalyzes synthesis of cholesterol.
1. Production of alcoholic beverages :
- Alcoholic beverages are produced by fermentation : liquors like beer, Whisky and wine.
- Saccharomyces cerevisiae var. ellipsoidis (Brewer’s Yeast) is used for fermenting malted cereals and fruit juices to produce ethanol.
- The beverages produced without distillation : Wine and Beer
- The beverages produced with distillation : Whisky, brandy and rum
Traditional drinks :
a. Toddy : Made by fermenting the sugar sap extracted from palm plants and coconut palm.
b. Fenny : Made by fermenting fleshy pedicels of cashew fruits.
2. Production of organic acids :
Microbes are used in the production of a number of organic acids.
- Aspergillus niger – Citric acid
- Aspergillus niger – Gluconic acid
- Rhizopus arrhizus – Fumaric acid
- Acetobacter aceti – Acetic acid (vinegar)
3. Production of vitamins :
(1) Vitamins : Organic nitrogenous compounds capable of performing many life-sustaining functions inside our body.
(2) Examples of vitamins : Thiamine, riboflavin, pyridoxine, folic acid, pantothenic acid, biotin, vitamin B12, ascorbic acid, beta-carotene (provitamin A) and ergosterol (provitamin D).
(3) Vitamins are manufactured by fermentation using different microbial sources :
- Vitamin B2 – i. Neurospora gossypii
ii. Eremothecium ashbyi
- Vitamin B12 – Pseudomonas denitrificans
- Vitamin C – Aspergillus niger
4. Production of Antibiotics :
(1) Antibiotics are secondary metabolites produced in small amounts by certain microbes (like bacteria, fungi and few algae), which inhibit growth of other microbial pathogens.
(2) They are used in treatment of deadly diseases like plague, whooping cough, diphtheria, leprosy, etc.
(3) Some common antibiotics and their microbial sources are as follows :
(4) Different antibiotics produced from following microbes:
- Chloromycetin → Streptomyces venezuelae
- Erythromycin → Streptomyces erythreus
- Penicillin → Penicillium chrysogenum
- Streptomycin → Streptomyces griseus
- Griseofulvin → Penicillium griseofulvum
- Bacitracin → Bacillus lichenijormis
- Oxytetracycline, Terramycin → Streptomyces aurifaciens
5. Production of Enzymes :
(1) Enzymes : Enzymes are biocatalyst proteins which accelerate biochemical processes.
(2) Uses of enzymes in various industries :
- Textile industry : To improve the quality of the fabrics.
- Pulp and paper industry : Biomechanical pulping and bleaching.
- Food industry : Fermentation for the production of bread and drinks such as wine and beer,
- Detergent industry : Lipase is used because of superior cleaning properties, to increase the brightness and to remove oil stains.
- The extraction of substances like carotenoids and olive oil.
- Enzymes are also used in cosmetics, animal feed and agricultural industries, among others.
- Streptokinase has fibrinolytic effect. Hence, it is used as a ‘clot buster’ in blood vessels of heart patients.
(3) Examples of microbial sources from which enzymes are produced :
- Saccharomyces cerevisiae – Invertase
- Sclerotinia libertine, Aspergillus niger – Pectinase
- Candida lipolytica – Lipase
- Trichoderma konigii – Cellulase
- Streptococcus spp. – Streptokinase
6. Gibberellin production :
(1) Gibberellin is a growth hormone produced by higher plants and a fungus named Giberella.
(2) Practical applications :
- To induce parthenocarpy in apple, pear, etc.
- Used in breaking the dormancy of seed and also in inducing flowering in Long Day Plants (LDP).
- To enlarge the size of grape fruits.
Microbes in Sewage Treatment –
1. Composition of Sewage carried out in drainage :
- Sewage consists of about water (99.5% to 99.9%) and inorganic and organic matter (0.1 to 0.5%) in suspended and soluble form.
- Composition of sewage varies depending upon the type of waste discharged into water from different industries.
- It includes human excreta, household waste, dissolved organic matter and even pathogenic microbes, discharged water from hospital waste, slaughter house waste, animal dung, discharge from industriad waste (contains toxic dissolved organic and inorganic chemicals), tannery, pharmaceutical waste, etc. also add to sewage.
- It contains bacteria from soil and pathogenic microorganisms (bacteria, viruses and protozoa) causing dysentery, cholera, typhoid, polio and infectious hepatitis and soil bacteria.
- Bacteria in sewage include coliforms, fecal Streptococci, anaerobic spore forming Bacilli and other types originating in the intestinal tract of humans.
2. Sewage treatment process includes four basic steps:
- Prelinfinary Treatment: It Includes Screening and Grit Chamber.
- Primary treatment (physical treatment) : It involves treatment of sewage in primary sedimentation tanks.
- Secondary treatment (biological treatment): It includes treatment of sewage in aeration tanks.
- Tertiary treatment : It involves passage of sewage water through settling tank and anaerobic sludge digesters.
Microbes in Energy Generation-
1. Biogas is a mixture of methane CH4 (50-60%), CO2 (30-40%), H2S (0-3%) and other gases (CO, N2, H2) in traces.
2. Substrates used for biogas production : Cattle dung (most commonly used substrate, a rich source of cellulose from plants), plant wastes, animal wastes, domestic wastes, agriculture waste, municipal wastes, forestry wastes, etc.
3. Biogas Production :
- Most commonly used models of biogas plants are developed by KVIC (Khadi and Village Industries Commission) and IARI (Indian Agricultural Research Institute).
- A typical biogas plant consists of digester and gas holder.
- Anaerobic digestion involves three processes : Hydrolysis or solublization, acidogenesis and methanogenesis.
4. Benefits of biogas :
- Biogas is a cheap, safe and renewable source of energy.
- It can be easily generated, stored and transported.
- It can be used for domestic lighting, cooking, street lighting as well as small scale industries.
- It burns with blue flame and without smoke.
- It helps to improve sanitation of the surrounding.
- It is eco-friendly and does not cause pollution.
- Sludge which is left over is used as a fertilizer.
Role of Microbes as Biocontrol Agents-
1. Biocontrol or biological control : It is the natural method of eliminating and controlling insects, pests and other disease-causing agents by using their natural, biological enemies.
2. Biocontrol agents : Microbes (bacteria, fungi, viruses and protozoans) act as biocontrol agents in three ways : they cause the disease to the pest or compete or kill them.
3. Some examples of Microbial bio-control :
- Bacillus thuringiensis (Bt) : It is used to get rid of butterfly, caterpillars.
- Trichoderma species : Effective bio-control agents against soil borne fungal plant pathogens.
4. Microbial Pesticides and their host:
|Caterpillars, Gypsy moth, ants, wasps, beetles||Viruses :
|Caterpillars, cabbage worms, adult beetle||Bacteria :
Bacillus thuringiensis (Bt)
A. unguiculata, mealy bugs, mites, white flies
|Grasshoppers, caterpillars, crickets||Protozoans :
5. Bioherbicides : They kill the weeds which compete with the main crop in the farm – land for water, space, minerals, light, air, etc. and also act as collateral hosts for several pathogens.
(1) Pathogenic fungi as mycoherbicides :
- Phytophthora palmivora – controls milk weed in orchards.
- Alternaria crassa – controls water hyacinth.
- Fusarium spp. – control most of the weeds.
(2) Bacterial pathogen as herbicides :
- Pseudomonas spp. – attacks several weeds
- Xanthomonas spp. – attacks several weeds
- Agrobacterium spp. – attacks several weeds
(3) Insects as herbicides :
- Tyrea moth – controls the weed Senecio jacobeac
- Cactoblastis cactorum – controls cacti weeds.
Role of Microbes as Biofertilizers-
1. Fertilizers are the nutrients required for plant growth and increase the productivity of cultivated plants.
2. Types of fertilizers :
- Inorganic fertilizers : They are synthetic fertilizers consisting of mineral salts of NPK mixed in specific proportion. If used excessively, they cause pollution of soil, air and groundwater.
- Organic fertilizers : They are biological in origin and include farm yard manure (FYM), compost and green manure.
3. For better and sustainable agricultural production, organic farming is practised and biofertilizers are used.
4. Biofertilizers include bacterial, cyanobacteria and fungi :
- Bacterial biofertilizers : These include bacteria and cyanobacteria
- Fungal biofertilizers
5. Types of Biofertilizers on the basis of nature and function :
(1) N2 fixing Biofertilizers :
- The nitrogen fixing microorganisms (diazotrophs) convert atmospheric nitrogen into nitrogenous compounds like nitrites and nitrates via ammonia.
- Symbiotic N2 fixing microorganisms : e.g. Rhizobium, Frankia.
These are mostly associated generally with roots of higher plants.
- Free-living or Non-Symbiotic N2 fixing microorganisms : e.g. Azotobacter, Clostridium, Beijerinkia, Klebsiella, etc.
(2) Phosphate solubilizing biofertilizers :
- These bacteria solubilize the insoluble inorganic phosphate compounds.
- e.g. Pseudomonas striata, Bacillus polymgxa, Agrobacterium, Microccocus, Aspergillus spp. etc.
(3) Compost making biofertilizers :
- In the composting process microorganisms break down organic matter into dark rich compost or humus.
- Microorganisms found in active compost: Bacteria, fungi, actinobacteria, protozoa and rotifers.
6. Cyanobacteria as biofertilizers :
- They may be free-living or symbiotic, heterocystous or non-heterocystous forms.
- Free living cyanobacteria : e.g. Anabaena, Nostoc, Plectonema, Oscillatoria.
- Symbiotic cyanobacteria associated with lichens : Anabaena, Nostoc and Tolypothrix.
- Symbiotic cyanobacteria associated with plants Azolla and Cycas : Anabaena.
7. Fungal biofertilizers :
(1) Mycorrhiza is a fungus which forms symbiotic association with the rhizomes and root of higher plants occurring in thick humid forests.
(2) Two types of mycorrhizal :
- Ectomycorrhizae : Mycelium of these fungi form mantle on the surface of the roots.
- Endomycorrhizae : They grow in between and within the cortical cells of roots.
(3) Benefits of Mycorrhiza :
- Selective absorption of P Zn, Cu, Ca, N, Mn, Br and Fe.
- Enhance water uptake.
- Induce growth by secreting hormones.
- Offer protection to host plant from other microbes, by secreting antibiotics.
(4) Nowadays, mycorrhiza are classified into 8 different types : Ectomycorrhizae,
Endomycorrhizae, Ectendo mycorrhizae, Orchidaceous mycorrhizae, Ericoid mycorrhizae, Arbutoid mycorrhizae, Monotrapoid mycorrhizae and Ophioglossoid mycorrhizae.
8. Biofertilizer microorganisms :
- Rhizobia : Nitrogen fixing bacteria in root nodules of leguminous plants.
e. g. R. leguminosarum is specific to pea and R. phaseoli is specific to beans.
- Azotobacter: Free living, nitrogen fixing bacterium associated with roots of grasses and certain plants.
- Azospirillum: Free living, aerobic nitrogen fixing bacterium associated with roots of corn, wheat and jowar.
- Anabaena : Filamentous nitrogen fixing cyanobacteria that forms symbiotic relationships with certain plants, such as the coralloid roots of Cycas and Anthoceros thallus. It has Heterocysts (Specialized colourless cells which are the sites for nitrogen fixation). It also fixes nitrogen in free living conditions.
- Azolla : A free-floating water fern. Anabaena present in the dorsal leaf lobe fixes nitrogen.
9. Benefits of Biofertilizers :
- Low cost and can be used by marginal farmers.
- Free from pollution hazards.
- Increase soil fertility.
- BGA secret growth promoting substances, organic acids, proteins and vitamins.
- Azotobacter supply nitrogen and antibiotics in the soil.
- Biofertilizers increase physico-chemical properties of soil-like texture, structure, pH, water holding capacity of soil by providing nutrients and organic matter.
Know the Scientist:
1. Dr. Norman E. Borlaug : Known as ‘Father of the Green Revolution’, ‘Agriculture’s greatest spokesperson’ and ‘The Man Who Saved a Billion Lives’.
A 1970 Nobel Laureate.
He saved 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’.
He introduced and developed high-yielding varieties of wheat in India.
He is pioneer in mutation breeding in India.
He developed new varieties of wheat like Sarbati, Sonora and NP165.
He advocated environmentally sustainable agriculture, sustainable food security and the preservation of biodiversity.