Microbes In Household Products

Microbes are integral to everyday household activities, primarily through fermentation. Lactic acid bacteria (LAB), such as Lactobacillus, ferment milk into curd, improving its nutritional value (especially Vitamin B12) and making milk proteins more digestible. LAB also help check the growth of harmful microbes in the gut. Fermentation by bacteria is also used in preparing dough for foods like dosa and idli, where CO2 production causes puffiness. Baker's yeast (Saccharomyces cerevisiae) is used to ferment bread dough, producing CO2 for leavening. Traditional beverages like 'toddy' are made by fermenting palm sap. Microbes also ferment fish, soybeans, and bamboo shoots for food. In cheesemaking, specific microbes impart unique textures and flavors; for instance, Propionibacterium sharmanii creates the large holes in Swiss cheese, and fungi like Penicillium roqueforti ripen Roquefort cheese.

Microbes In Industrial Products

Microbes are extensively used in industrial processes to produce valuable products on a large scale using fermentors.

Fermented Beverages

Yeasts, particularly Saccharomyces cerevisiae (brewer's yeast), are used to ferment malted cereals and fruit juices to produce alcoholic beverages like wine, beer, whisky, brandy, and rum. Wine and beer are produced without distillation, while whisky, brandy, and rum are distilled from fermented products.

Antibiotics

Antibiotics, chemicals produced by some microbes that inhibit or kill disease-causing microbes, are crucial in medicine. Alexander Fleming's chance discovery of penicillin from the mold Penicillium notatum revolutionized medicine. Later, Ernest Chain and Howard Florey developed methods for its large-scale production. Other antibiotics have since been discovered from various microbes, significantly improving the treatment of infectious diseases like plague, diphtheria, and leprosy.

Chemicals, Enzymes And Other Bioactive Molecules

• Organic Acids: Microbes produce valuable organic acids, such as citric acid (by Aspergillus niger), acetic acid (by Acetobacter aceti), butyric acid (by Clostridium butylicum), and lactic acid (by Lactobacillus).
• Enzymes: Lipases are used in detergents for stain removal. Pectinases and proteases clarify bottled fruit juices.
• Bioactive Molecules:
  • Streptokinase: Produced by Streptococcus and genetically modified, it acts as a 'clot buster' to treat heart attacks by dissolving blood clots.
  • Cyclosporin A: An immunosuppressive agent produced by the fungus Trichoderma polysporum, used in organ transplantation to prevent rejection.
  • Statins: Produced by the yeast Monascus purpureus, they lower blood cholesterol by inhibiting cholesterol synthesis.

Microbes In Sewage Treatment

Sewage, primarily human excreta and wastewater, contains large amounts of organic matter and pathogenic microbes. It is treated in Sewage Treatment Plants (STPs) before disposal to reduce pollution.

Primary Treatment

This stage involves the physical removal of solid particles through filtration and sedimentation. Floating debris is removed by filtration, and grit (soil, pebbles) is settled out. The settled solids form the primary sludge, and the liquid part is called the effluent.

Secondary Treatment Or Biological Treatment

The primary effluent is passed into large aeration tanks where aerobic microbes (bacteria and fungi) grow in flocs. These microbes consume the majority of the organic matter, significantly reducing the Biochemical Oxygen Demand (BOD). BOD is a measure of the oxygen required to decompose organic matter, indicating the level of pollution; lower BOD means less pollution. After the organic matter is reduced, the flocs (activated sludge) settle in a settling tank. A portion of this activated sludge is recycled to the aeration tank to inoculate new effluent. The remaining sludge is transferred to anaerobic digesters, where anaerobic bacteria further break down organic matter, producing biogas (a mixture of methane, hydrogen sulfide, and carbon dioxide). The treated effluent, with significantly reduced BOD, is then discharged into natural water bodies.

Microbes In Production Of Biogas

Biogas, a mixture of gases (primarily methane, along with CO2 and H2), is produced by anaerobic microbial activity, particularly methanogens (like Methanobacterium). These microbes thrive in environments rich in organic matter, such as anaerobic sludge in sewage treatment plants and the rumen of cattle. In the rumen, methanogens help break down cellulose in the cattle's diet. Cattle dung, rich in methanogens, is collected in biogas plants (concrete tanks). The dung slurry ferments anaerobically, producing biogas, which is collected in a floating cover and used as a fuel for cooking and lighting. The remaining spent slurry is an excellent fertilizer.

Microbes As Biocontrol Agents

Biological Control Of Pests And Diseases

Biocontrol involves using biological methods to manage pests and diseases, reducing reliance on harmful chemical pesticides and insecticides. Organic farming emphasizes biodiversity, creating a balanced ecosystem where beneficial predators and parasites help control pest populations naturally. Key biocontrol agents include:

• Ladybird Beetles and Dragonflies: Effective against aphids and mosquitoes, respectively.
• Bacillus thuringiensis (Bt): A bacterium whose spores, when sprayed on plants, are ingested by insect larvae (e.g., caterpillars). Bt produces toxins in the larval gut, killing them while leaving other insects unharmed. Genetic engineering has enabled the introduction of Bt toxin genes into plants, creating pest-resistant crops like Bt cotton.
• Fungi (e.g., Trichoderma): These free-living fungi common in root ecosystems are effective biocontrol agents against several plant pathogens.
• Baculoviruses: Viruses that specifically infect insects and other arthropods. They are useful for species-specific, narrow-spectrum pest control, having no negative impact on non-target organisms or the environment.

These biological methods are more sustainable and environmentally friendly than chemical pest control.

Microbes As Biofertilisers

Biofertilizers are living organisms that enrich soil nutrient quality, reducing the need for chemical fertilizers. They are derived from bacteria, fungi, and cyanobacteria.

• Bacteria:
  • Rhizobium: Forms symbiotic nitrogen-fixing nodules on the roots of leguminous plants.
  • Free-living soil bacteria: Such as Azospirillum and Azotobacter, fix atmospheric nitrogen, enriching the soil.
• Fungi (Mycorrhizae): Fungi like those in the genus Glomus form symbiotic associations with plant roots. They absorb phosphorus from the soil and provide it to the plant, also offering benefits like pathogen resistance and drought tolerance. The fungus benefits by receiving carbohydrates from the plant.
• Cyanobacteria (Blue-green algae): Such as Anabaena, Nostoc, and Oscillatoria, are widespread and fix atmospheric nitrogen. They are important biofertilizers in paddy fields and also add organic matter to the soil, increasing its fertility.

The use of biofertilizers is a crucial aspect of organic farming and sustainable agriculture.

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