Notes-Part-3-Class-12-Biology-Chapter-11-Enhancement in Food Production-Maharashtra Board

Microbes in food preparation :

Many food preparations made at home involves the use of microorganisms.

• The microbes Lactobacilli are used in the preparation of dhokla from gram flour and buttermilk by the process of fermentation.
• Dosa and idlis are prepared by using batter of rice and black gram which is fermented by air borne Leuconostoc and Streptococcus bacteria.
• Large, fleshy fruiting bodies of some mushrooms and truffles are directly used as food. It is sugar free, fat free food rich in proteins, vitamins, minerals and amino acids. It is food with low calories.
• Curd is prepared by inoculating milk with Lactobacillus acidophilus. Lactic acid produced during fermentation causes coagulation and partial digestion of milk protein casein and milk turns into curd.
• Buttermilk is the acidulated liquid left after churning of butter from curd, is called buttermilk.
• 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

Production of Alcoholic Beverages :

• Alcoholic beverages are the products of alcoholic fermentation of particular substrates.
• Tubular tower fermenters are used to produce alcoholic beverages on a large scale.
• Beer is produced from barley by fermentation.
• For the production of beer, strains of Saccharomyces cerevisiae are used.
• Wine is prepared from grapes.
• Whisky is prepared by fermenting mixed grains of wheat, barley and corn followed by the distillation of the products of fermentation.
• Liquors like beer, wine are produced without distillation.
• Whisky, rum and brandy are distilled alcoholic beverages.
• Traditional drinks Toddy is prepared by fermenting the sugar sap extracted from palms and coconut palms. Fenny is fermented by fleshy pedicels of cashew fruits.

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)

Production of vitamins :

Vitamins : Organic nitrogenous compounds capable of performing many life-sustaining functions inside our body.

The microbes are involved in the industrial production of vitamins like thiamine (vitamin B₁), riboflavin (vitamin B₂), pyridoxine, folic acid, pantothenic acid, biotin, vitamin B₁₂, ascorbic acid (Vitamin C), beta-carotene (provitamin A) and ergosterol (provitamin D).

Examples of some vitamins produced by fermentation using different microbial sources are :

• Vitamin B₂— Neurospora gossypii, Eremothecium ashbyi
• Vitamin B₁₂ — Pseudomonas denitrificans
• Vitamin C — Aspergillus niger

Production of Antibiotics :

• Antibiotics are secondary metabolites produced in small amounts by certain microbes (like bacteria, fungi and few algae), which inhibit growth of other microbial pathogens.
• They are used in treatment of deadly diseases like plague, whooping cough, diphtheria, leprosy, etc.

Some common antibiotics and their microbial sources are as follows :

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.

Name of the enzyme and Microbial source

• Invertase : Saccharomyces cerevisiae
• Pectinase : Sclerotinia libertine, Aspergillus niger
• Lipase : Candida lipolytica
• Cellulase : Trichoderma konigii

Applications of gibberellins are as follows :

• Gibberellins induce parthenocarpy in fruits like pear and apple.
• Gibberellins promote growth by stem elongation.
• They break the dormancy of seeds.
• They induce flowering in long day plants in short day conditions.
• They are used to enlarge the size of grapes.

Sewage treatment :

Before waste water is made available for human use, it has to be treated properly, so as to remove organic matter, inorganic salts and pathogens as well.

Sewage treatment process includes four basic steps :

• Preliminary 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.

Effluents from these digesters are released in natural water bodies like rivers and streams after chlorination which kills pathogenic bacteria. Digested sludge is then disposed.

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.
• Raw materials like cow dung is mixed with water in equal proportion to make slurry which is fed into the digester through a side opening (charge pit).

Anaerobic digestion involves three processes : Hydrolysis or solublization, acidogenesis and methanogenesis.

• Hydrolysis or solubilization : In initial stage raw material (cattle dung) is mixed with water in equal proportion to make slurry which is then fed into the digester. Here anaerobic hydrolyzing bacteria like Clostridium and Pseudomonas hydrolyse carbohydrates into simple sugars, proteins into amino acids and lipids into fatty acids.
• Acidogenesis : Facultative and obligate anaerobic, acidogenic bacteria convert simple organic substances into acids like formic acid, acetic acid, H₂ and CO₂
• Methanogenesis : Anaerobic methanogenic bacteria like Methanobacterium, Methanococcus convert acetate, H₂ and CO₂ into Methane, CO₂ and H₂O and other products.

12 mol CH₃COOH —> 12CH₄ + 12CO₂

4 mol H.COOH —> CH₄ + 3CO₂ + 2H₂O

CO₂ + 4H₂ —> CH₄ + 2H₂O

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.

Microbial Pesticides and their host :

The corelation is depicted as per the following table :

Bacterial biofertilizers :

Nitrogen fixing bacterial biofertilizers:

• They convert atmospheric nitrogen into compounds of nitrogen like ammonia, nitrites and nitrates.
• The nitrogen fixing bacteria Rhizobium forms symbiotic association with roots of leguminous plants.
• Free living nitrogen fixing bacteria are Azotobacter and Azospirillum.

Phosphate solubilizing biofertilizers :

• They are the bacteria which solubilize the insoluble inorganic phosphate compound. e.g. Pseudomonas striata, Bacillus polymyxa, Agrobacterium, Microccocus, Aspergillus spp., etc.
• Bacteria are also involved in composting.

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.

Cyanobacterial biofertilizers :

• They are nitrogen fixing biofertilizers.
• Heterocysts are the site of nitrogen fixation.
• Free living cyanobacteria are Anabaena. Nostoc, Tolypothrix, Plectonema, Oscillatoria.
• Anabaena and Nostoc have symbiotic relationship with lichens
• Anabaena is also syrnbiotically associated with Azolla and Cycas.

Fungal biofertilizers :

Mycorrhiza is a fungus which forms symbiotic association with the rhizomes and root of higher plants occurring in thick humid forests.

Two types of mycorrhiza :

• 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.

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.
• Nowadays, mycorrhiza are classified into 8 different types : Ectomycorrhizae, Eudomycorrhizae, Ectendo mycorrhizae, Orchidaceous mycorrhizae, Ericoid mycorrhizae, Arbutoid mycorrhizae, Monotrapoid mycorrhizae and Ophioglossoid mycprrhizae.

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.