UNIT - III Microbes in 9 Human Welfare CHAPTER Saccharomyces cerevisiae, a species of used in baking and industry.

Chapter outline

9.1 Microbes in household products Microbes such as , fungi, 9.2 Microbes in industrial products protozoa, certain algae, viruses, viroids and 9.3 M icrobes in sewage treatment and prions are some of the major components energy generation of the biological system on Earth. Several microorganisms are beneficial and contribute 9.4 Microbes in the production of biogas to human welfare. Microbes are present 9.5 M icrobes as bio-control agents and everywhere – in soil, water, air and within bio-fertilisers bodies of animals and plants. Microbes like 9.6 Bioremediation bacteria and fungi can be grown on nutritive media to form colonies which can be visibly seen. Some of the microbes useful to human welfare are discussed here. Learning objectives 9.1 Microbes in household ➢ Differentiates probiotics from products pathogens. In every day life, microbes and their ➢ Understands the use of microbes in products are used in the preparation of idli, household products. dosa, , curd, yogurt, dough, , ➢ Learns about antibiotic , etc., Bacteria like Lactobacillus production and fermented acidophilus, L. lactis and Streptococcus lactis beverages. commonly called lactic acid bacteria (LAB) ➢ Realizes the importance are probiotics which check the growth of of microbes in sewage pathogenic microbes in the stomach and treatment and energy other parts of the digestive tract. generation. The LAB bacteria grows in milk and ➢ Learns the role of bio-fertilisers convert it into curd, thereby digesting the milk in farming. protein casein. A small amount of curd added ➢ Realizes the applications of microbes in to fresh milk as a starter or inoculum contains bio-remediation. millions of Lactobacilli, which under suitable

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TN_GOVT_XII_Zoology_chapter 9.indd 155 25-02-2019 18:40:20 o temperature (≤40 C) multiply and convert di-oxide, which is responsible for leavening of milk into curd. Curd is more nutritious than dough. When leavened dough is baked, both milk as it contains a number of organic acids carbon-di-oxide and ethyl alcohol evaporate and vitamins. making the bread porous and soft.

Prebiotics are compounds Single cell protein (SCP) in food (fibers) that induce Single cell protein refers to edible the growth or activity of unicellular microorganisms like Spirulina. beneficial microorganisms. Protein extracts from pure or mixed cultures Probiotics are live of algae, , fungi or bacteria may be used microorganisms intended to provide health as ingredient or as a substitute for protein rich benefits when consumed, generally by foods and is suitable for human consumption improving or restoring the gut flora. or as animal feed. Yogurt is produced by bacterial 9.2 Microbes in industrial of milk, and lactic acid is products produced as a byproduct. Microorganisms Microbes are used to synthesize a number such as Streptococcus thermophilus and of products valuable to human beings. Products Lactobacillus bulgaricus coagulate the milk like beverages, antibiotics, organic acids, amino protein and convert the lactose in the milk acids, vitamins, biofuels, single cell protein, to lactic acid. The flavour in yogurt is due to enzymes, steroids, vaccines, pharmaceutical acetaldehyde. drugs, etc., are produced in industries. Cheese is a dairy product produced in a Production on a large scale requires growing wide range of flavours, textures and is formed microbes in very large vessels called fermentors. by coagulation of the milk protein, casein. A fermentor (bioreactor) is a closed vessel with During cheese production, milk is usually adequate arrangement for aeration, agitation, acidified and the enzyme rennet is added to temperature, pH control and drain or overflow cause coagulation. The solids are separated and vent to remove the waste biomass of cultured pressed to form cheese. Most cheese are made microorganisms along-with their products. with a starter bacteria, Lactococcus, Lactobacillus or Streptococcus. 9.2.1 Antibiotic production Paneer (cottage cheese) is fresh cheese Antibiotics are chemical substances common in South Asia, especially in India. produced by microorganisms which can kill It is made by curdling milk with lemon juice, or retard the growth of other disease causing vinegar and other edible acids. Large holes in microbes even in low concentration. Antibiotic Swiss cheese is due to the production of large means “against life”. Antibiotics are used to treat amount of carbon-di-oxide by the bacterium diseases such as plague, meningitis, diphtheria, Propionibacterium shermanii. syphilis, leprosy, tuberculosis etc., Selman The dough used in the preparation of idlis and Waksman discovered Streptomycin and was the dosas are fermented by the bacteria Leuconostoc first to use the term antibiotic“ ” in 1943. mesenteroides whereas the dough used in While working on Staphylococci bacteria, bread making is fermented by Saccharomyces Alexander Fleming observed a green mould cerevisiae (Baker’s Yeast). Fermentation of growing in one of his unwashed culture plates glucose mainly forms ethyl alcohol and carbon- around which Staphylococci could not grow. He

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TN_GOVT_XII_Zoology_chapter 9.indd 156 25-02-2019 18:40:20 found that it was due to a chemical produced by the mould and he named it as penicillin, Hypersensitivity reaction which was the first antibiotic discovered by is a major problem with Alexander Fleming in 1926 (Fig. 9.1). Penicillin the use of penicillin, is produced by the fungi Penicillium notatum resulting in nausea, and Penicillium chrysogenum. It is bactericidal vomiting, wheezing and (antibiotics that kill bacteria) in action and ultimately cardiovascular collapse. To check inhibits the synthesis of the bacterial cell wall. the sensitivity reaction, doctors use a needle to prick the forearm of the patients to give a Penicillin is also referred as the “queen weak dose of penicillin. An itchy red region in of drugs” and its full potential as an effective the forearm is an indication that the patient antibiotic was established much later by is allergic to penicillin. This test is important Earnest Chain and Howard Florey when they before administration of penicillin to a patient. treated the wounded soldiers in World War II with penicillin. Fleming, Chain and Florey Tetracycline is a broad spectrum were awarded the Nobel prize in 1945 for the bacteriostatic antibiotic (antibiotics that limit the discovery of penicillin. growth of bacteria) that inhibits microbial protein synthesis. Chlortetracycline is the first antibiotic Antibiosis is the property of antibiotics to of this group, isolated from the cultures of kill microorganisms. Streptomyces aureofaciens. Streptomycin is Broad-spectrum antibiotics act against a a broad spectrum antibiotic isolated from wide range of disease-causing bacteria. the actinomycetes, Streptomyces griseus. It is Narrow-spectrum antibiotics are active bactericidal against both gram positive and against a selected group of bacterial types. gram negative bacteria, especially against Mycobacterium tuberculosis. Antibiotics, such g

n as erythromycin, chloromycetin, griseofulvin, i neomycin, kenamycin, bacitracin, etc., are also m

e isolated as microbial products. l F

r Antibiotic resistance

e Antibiotic resistance occurs when bacteria d

n develop the ability to defeat the drug designed

a to kill or inhibit their growth. It is one of the x most acute threat to public health. Antibiotic e l resistance is accelerated by the misuse and A over use of antibiotics, as well as poor infection prevention control. Antibiotics should be used H only when prescribed by a certified health Penicillium N S chrysogenum professional. When the bacteria become O N O resistant, antibiotics cannot fight against them OH and the bacteria multiply. Narrow spectrum O antibiotics are preferred over broad spectrum antibiotics. They effectively and accurately target StaStaphylococcusp aureus specific pathogenic organisms and are less likely Fig. 9.1 Discovery of penicillin to cause resistance. "Superbug" is a term used to

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TN_GOVT_XII_Zoology_chapter 9.indd 157 25-02-2019 18:40:21 describe strains of bacteria that are resistant to Alcohol content in various beverages the majority of antibiotics commonly used today. • contains 3 to 5 percent of alcohol. 9.2.2 Fermented beverages • contains 9 to 14 percent alcohol. Microbes especially yeast is being used Wine coolers are made of wine mixed from time immemorial for the production with carbonated water and flavourings. of beverages like wine, beer, whisky, Wine coolers have about 4 to 6 percent and rum. Wine is among the oldest alcoholic alcohol. beverages known and is produced by • Distilled spirits such as whiskey, gin, fermentation of fruit juice by yeast. Zymology scotch and usually contain 35 is an applied science which deals with the to 50 percent alcohol. biochemical process of fermentation and its practical uses. In some parts of South India, a traditional Saccharomyces cerevisiae commonly drink called pathaneer is obtained from called brewer’s yeast is used for fermenting fermenting sap of palms and coconut trees. A malted cereals and fruit juices to produce common source is tapping of unopened spadices various alcoholic beverages. Wine and beer of coconut. It is a refreshing drink, which on are produced without distillation, whereas boiling produces jaggery or palm . When whisky, brandy and rum are obtained by pathaneer is left undisturbed for few hours it fermentation and distillation. gets fermented to form toddy with the help of naturally occurring yeast, to form a beverage The Pasteur effect is the that contains 4 percent alcohol. After 24 hours inhibiting effect of oxygen toddy becomes unpalatable and is used for the on the fermentation production of vinegar. process. Saccharomyces cerevisiae is the major producer of (C2H5OH). It is used for Oenology is the science and study of industrial, laboratory and fuel purposes. So wine and wine making. Wine is made from ethanol is referred to as industrial alcohol. the fermentation of grape juice. Grape juice is Bacteria such as Zymomonas mobilis and Sarcina fermented by various strains of Saccharomyces ventriculi are also involved in ethanol production. cerevisiae into alcohol. Grape wine is of two types, The principal substrates for the commercial red wine and white wine. For red wine, black production of industrial alcohol include molasses grapes are used including skins and sometimes or corn, potatoes and wood wastes. The process the stems also are used. In contrast white wine is of ethanol production starts by milling a feed produced only from the juice of either white or stock followed by the addition of dilute or fungal red grapes without their skin and stems. amylase (enzyme) from Aspergillus to break down the starch into fermentable . Yeast Beer is produced from germinated barley is then added to convert the sugars to ethanol malt grain by Saccharomyces carlsbergensis which is then distilled off to obtain ethanol which or Saccharomyces cerevisiae. Rum is made is upto 96 percent in concentration. The two from fermented sugarcane or molasses or most common type of biofuels in use today are directly from sugarcane juice by Saccharomyces ethanol and biodiesel, both of them represent th