Understand how microbes contribute to household products.
Grasp the industrial significance of microbial products.
Comprehend microbial roles in sewage treatment and biogas production.
Recognize the utility of microbes as biocontrol agents and biofertilizers.
Microbes in Household Products Microbes play a crucial role in producing several household products that we use daily, especially in food production:
Curd Production: Microorganisms such as Lactobacillus and other lactic acid bacteria (LAB) are responsible for the conversion of milk into curd. During the process, LAB produce acids that coagulate and partially digest the proteins in milk, enhancing the nutritional quality by increasing the vitamin B12 content. LAB are also beneficial for inhibiting harmful microbes in the stomach.
Dough Fermentation: The puffed-up appearance of dough used for foods like dosa and idli results from CO2 produced by fermenting bacteria. The bacteria responsible for fermentation naturally occur in the environment, playing a key role in gas production via metabolic pathways.
Bread Making: Saccharomyces cerevisiae, commonly called baker’s yeast, ferments the dough used in bread production, resulting in the desired texture.
Traditional Drinks and Foods: Fermentation of foods like toddy (a traditional Indian drink), fish, soybean, and bamboo shoots is driven by microbes, making them safe for consumption and improving their flavor.
Cheese Production: Microbes are essential in cheese production, creating various textures and flavors. For example, Propionibacterium sharmanii produces large amounts of CO2, forming the characteristic holes in Swiss cheese, while fungi grow on Roquefort cheese to impart a specific flavor.
Microbes in Industrial Products Microbes are also employed on an industrial scale for producing various valuable substances:
Fermented Beverages: Since ancient times, yeasts such as Saccharomyces cerevisiae (brewer’s yeast) have been used to produce alcoholic beverages. The fermentation of malted cereals and fruit juices leads to ethanol production. Depending on the raw material and processing method, various alcoholic drinks such as wine and beer (without distillation) and whisky, brandy, and rum (with distillation) are produced.
Antibiotics: Antibiotics are among the most important contributions of microbes to human health. For example, Penicillin, discovered by Alexander Fleming, is produced by Penicillium notatum and was later refined by Ernest Chain and Howard Florey. It revolutionized the treatment of bacterial infections during World War II.
Chemicals and Enzymes: Microbes also produce organic acids like citric acid (Aspergillus niger), acetic acid (Acetobacter aceti), and lactic acid (Lactobacillus). Additionally, enzymes like lipases are used in detergents, and pectinases and proteases are used in the production of clear fruit juices.
Bioactive Molecules: Microbes like Streptococcus produce streptokinase, a clot-buster for treating heart attack patients. Cyclosporin A, an immunosuppressive agent used in organ transplants, is produced by Trichoderma polysporum. Statins from Monascus purpureus lower blood cholesterol by inhibiting an enzyme involved in cholesterol synthesis.
Important Concept Antibiotics not only kill harmful microbes but also significantly improve human health by preventing diseases like diphtheria, whooping cough, and leprosy.
Microbes in Sewage Treatment Wastewater, primarily containing human excreta, is processed before being discharged into natural water bodies to prevent pollution. Microbes play a vital role in treating sewage through two stages:
Primary Treatment: Involves physical removal of large particles through filtration and sedimentation. The settled solids form primary sludge, while the supernatant is taken for further treatment.
Secondary Treatment: Involves biological processes using aerobic microbes in aeration tanks. These microbes, in the form of flocs, digest organic matter, reducing the biochemical oxygen demand (BOD). After this, the effluent is sent to a settling tank, where the bacterial flocs form activated sludge. A portion of this sludge is returned to the aeration tank, while the remainder is digested anaerobically, producing methane, hydrogen sulfide, and carbon dioxide—collectively known as biogas. The treated water is then released into natural water bodies.
Important Concept BOD (Biochemical Oxygen Demand) is a measure of the organic matter present in water. High BOD indicates high pollution potential.
Microbes in Biogas Production Biogas is produced by anaerobic digestion of organic waste by methanogenic bacteria, predominantly producing methane:
Biogas Production: Methanogens such as Methanobacterium thrive in anaerobic conditions and break down cellulosic material to produce biogas. These bacteria are commonly found in the rumen of cattle and the anaerobic sludge of sewage treatment plants.
Biogas Plant Structure: A biogas plant typically consists of a concrete tank where bio-wastes are collected and mixed with a slurry of cattle dung. Microbial activity in the tank produces gas, which is collected and used as fuel for cooking and lighting. The spent slurry can be used as fertilizer, making this an efficient system for rural areas.
Development of Biogas Technology: In India, the Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC) were instrumental in developing biogas technology, particularly for rural areas where cattle dung is readily available.
Microbes as Biocontrol Agents Biocontrol involves using natural predators, parasites, and pathogens to control pests and diseases in agriculture:
Biocontrol Agents: This approach, favored by organic farmers, promotes biodiversity and a balance in the ecosystem. Instead of eliminating pests entirely, they are kept in check through natural predation. This reduces the need for chemical pesticides that harm the environment and human health.
Microbial Control: Microbes like Bacillus thuringiensis (Bt) are used to control butterfly caterpillars in agriculture. Bt spores, mixed with water and sprayed on crops, release toxins in the caterpillars’ guts, killing them without affecting other insects. Bt genes have been introduced into crops like Bt-cotton, making them resistant to pests.
Fungal Biocontrol: Fungi like Trichoderma act as biocontrol agents against several plant pathogens. These fungi live in the root ecosystem and promote plant growth by protecting against pathogens.
Viral Biocontrol: Baculoviruses, particularly Nucleopolyhedrovirus, are used to control specific insect pests without harming non-target organisms like plants and animals. This selective control is ideal for integrated pest management (IPM) programs, particularly in ecologically sensitive areas.
Microbes as Biofertilisers Biofertilizers are microorganisms that enrich soil nutrients, promoting sustainable agriculture:
Nitrogen Fixing Bacteria: Rhizobium forms symbiotic relationships with leguminous plants, fixing atmospheric nitrogen into organic forms usable by plants. Other free-living bacteria like Azospirillum and Azotobacter also fix nitrogen, enhancing soil fertility.
Mycorrhizal Fungi: Fungi like Glomus form symbiotic associations with plant roots (mycorrhiza), absorbing phosphorus and transferring it to the plant. This relationship also makes plants more resistant to root pathogens, salinity, and drought.
Cyanobacteria: Autotrophic microbes like Anabaena, Nostoc, and Oscillatoria can fix atmospheric nitrogen and improve soil fertility in paddy fields. These biofertilizers are widely used by farmers to reduce dependence on chemical fertilizers.
Important Concept Biofertilizers enhance soil fertility without causing the environmental damage associated with chemical fertilizers.
Comprehensive Table Comparing Key Microbes and Their Uses