TLDR;
This video explores the beneficial roles of microbes in human welfare, moving beyond the common perception of them as harmful entities. It covers their applications in household products, industrial processes, sewage treatment, biogas production, and as biofertilisers and biocontrol agents in agriculture. The lecture highlights specific examples and processes, emphasising the diverse and essential contributions of bacteria, fungi, and other microorganisms to our daily lives and the environment.
- Microbes are essential in producing household items like yoghurt, cheese, and fermented foods.
- Industries utilise microbes for producing alcohol, enzymes, organic acids, and antibiotics.
- Microbes play a crucial role in sewage treatment, biogas production, and as biofertilisers.
Introduction: Microbes - More Than Just Bad Guys [0:00]
The video introduces the concept that microbes, often viewed negatively, play significant beneficial roles in human welfare. The lecture aims to explore these positive aspects, demonstrating how microorganisms like bacteria, fungi, and viruses are used to our advantage. The chapter sets the stage for discussing the various applications of microbes in everyday life and industry.
Microbes in Household Products [1:02]
This section details how microbes are used in common household products. Lactobacillus bacteria are used in making yoghurt through lactic acid fermentation, which curdles the milk protein casein. Different types of cheese are produced using specific microbes: Swiss cheese is made with Propionibacterium shermanii, while Roquefort and Camembert cheeses are made using Penicillium fungi. Additionally, bacteria like Leuconostoc and Streptococcus are used in fermenting the batter for dosa and idli, and Saccharomyces cerevisiae (baker's yeast) is used in bread making, producing carbon dioxide that gives bread its fluffy texture. Fermented foods like Toddy, made from palm sap, and soy products like tofu are also mentioned.
Microbes in Industrial Production [2:31]
The lecture moves on to the industrial applications of microbes, starting with alcohol production, where fungi like Saccharomyces cerevisiae (also known as brewer's yeast) are used for alcoholic fermentation. It distinguishes between non-distilled alcohols like wine (6-10% alcohol) and beer (5-12% alcohol), which are naturally fermented, and distilled alcohols like vodka, whisky, and rum, which require further processing to increase alcohol content. Enzymes produced by bacteria and fungi are also discussed, such as lipases used in detergents to clean clothes and pectinases and proteases used to clarify bottled juices. Streptokinase, derived from Streptococcus, is used as a clot-buster, while Cyclosporin A, from the fungus Trichoderma, is used as an immunosuppressant in organ transplants. Statins, obtained from the yeast Monascus purpureus, are used to lower cholesterol levels by competitively inhibiting cholesterol-synthesising enzymes. Various organic acids like citric acid (from Aspergillus niger), butyric acid (from Clostridium butylicum), acetic acid (from Acetobacter aceti), and lactic acid (from Lactobacillus) are also produced using microbes.
Antibiotics: A Serendipitous Discovery [5:37]
The discovery of antibiotics is presented as a chance event. Alexander Fleming discovered penicillin when he noticed that a Penicillium fungus contaminated his Staphylococcus bacterial culture, killing the bacteria. Chain and Florey further developed penicillin for medicinal use. In 1945, Fleming, Chain, and Florey were awarded the Nobel Prize for this groundbreaking discovery. Antibiotics are also derived from bacteria, with Streptomyces being a major source. Examples include streptomycin and chloramphenicol.
Microbes in Sewage Treatment [7:05]
This section explains how microbes are used in sewage treatment plants to clean wastewater. The process is divided into primary, secondary, and tertiary treatments. Primary treatment involves physical processes like sequential filtration to remove floating debris and sedimentation in settling tanks to remove grit and sand, resulting in primary sludge and primary effluent. Secondary treatment uses microbes: the primary effluent is transferred to aeration tanks where aerobic bacteria and fungal filaments form flocs and degrade organic impurities. The mixture is then moved to settling tanks where the flocs settle as activated sludge, and the remaining water is the secondary effluent, which can be released into rivers. A portion of the activated sludge is recycled into the aeration tank as an inoculum, while the remaining sludge is sent to anaerobic digesters containing methanogenic archaea that break down the aerobic bacteria and fungi, producing biogas (methane). The Ganga Action Plan and Yamuna Action Plan, initiatives by the government, aim to clean these rivers using sewage treatment.
Microbes in Biogas Production [11:01]
Biogas, composed of 60-70% methane, 30-40% carbon dioxide, and traces of other gases, is produced by methanogens, a type of archaea. These anaerobic bacteria are found in marshy areas, rice fields, and the rumen of cattle, where they aid in cellulose digestion. A biogas plant consists of a 6-7 feet deep pit where methanogens are introduced and sealed to cut off oxygen supply, allowing methane gas production. Organisations like IARI and KVIC promote biogas usage in India.
Microbes as Biocontrol Agents [12:15]
The lecture discusses the use of microbes as biocontrol agents in integrated pest management and organic farming. Natural predators are used to control pests instead of chemical pesticides. Examples include using ladybirds to control aphids, dragonflies to control mosquitoes, and Trichoderma fungi to protect plant roots from pathogens. Bacillus thuringiensis spores are used to control cotton bollworms, and baculoviruses are used as narrow-spectrum insecticides that specifically target certain insects without harming non-target species, birds, mammals, reptiles, or humans.
Microbes as Biofertilisers [13:58]
Microbes are also used as biofertilisers to enrich soil fertility. Bacteria, cyanobacteria (blue-green algae), and fungi are used for this purpose. Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, which plants can use. These bacteria can be free-living (e.g., Azotobacter, Azospirillum, Beijerinckia, Clostridium) or symbiotic (e.g., Rhizobium in legume roots, Frankia in Alnus and Casuarina roots). Cyanobacteria like Nostoc and Anabaena are also effective nitrogen fixers, functioning both as free-living and symbiotic organisms (e.g., Anabaena with Azolla, an aquatic fern, and with cycads). Azolla is a free-living nitrogen-fixing cyanobacterium commonly found in rice paddies. Fungi form symbiotic associations with plant roots known as mycorrhizae, which increase the surface area for water and mineral absorption, particularly phosphorus. Glomus is a common fungus in mycorrhizal associations.