Detailed Notes Chapter 8- Microbes In Human Welfare

 Chapter 8- Microbes In Human Welfare

Introduction

1. Microbial Diversity: Microbes are found in various biological systems on Earth, alongside macroscopic plants and animals. In Class XI, you likely studied the diversity of living organisms, including microorganisms. Microbes are present in different kingdoms of life.

2. Kingdoms Containing Microorganisms: Microorganisms are found in multiple kingdoms, including:

   • Bacteria: Single-celled organisms that can be found virtually everywhere, from soil and water to inside living organisms and extreme environments.
   • Fungi: Including yeasts and molds, fungi comprise a diverse group of microorganisms found in various habitats.
   • Protists: This kingdom includes diverse microscopic organisms such as protozoa, which are often found in aquatic environments.

3. Microscopic Nature of Some Microbes: While many microbes are visible to the naked eye, some are only microscopic in size. This includes certain bacteria, fungi, and protists, as well as microscopic animal and plant viruses, viroids, and prions.

4. Ubiquitous Presence: Microbes can be found in a wide range of environments, including soil, water, air, inside living organisms (including humans, animals, and plants), and extreme environments such as geysers, deep soil layers, and acidic environments.

5. Culturing Microbes: Some microbes, like bacteria and many fungi, can be grown on nutritive media to form visible colonies. These colonies can be observed with the naked eye and are useful for studying microorganisms.

6. Microbial Diseases: Microbes are responsible for causing a large number of diseases in humans, animals, and plants. Chapter 7 likely covered the various ways in which microbes can cause diseases.

7. Beneficial Microbes: Despite the negative associations with diseases, not all microbes are harmful. Many microbes are beneficial and contribute to human welfare in various ways. Some of these contributions include:

   • Bioremediation: Microbes help clean up pollutants and contaminants from the environment.
   • Fermentation: Microbes are used in food and beverage production through processes like fermentation.
   • Biotechnology: Microbes are utilized in various biotechnological processes, including the production of pharmaceuticals, enzymes, and biofuels.

8.1 MICROBES IN HOUSEHOLD PRODUCTS

1. Curd Production:

   • Microorganisms like Lactobacillus and other lactic acid bacteria (LAB) are used to convert milk into curd.
   • LAB ferment lactose in milk, producing lactic acid, which coagulates and partially digests milk proteins.
   • This process improves the nutritional quality of milk by increasing vitamin B12.
   • LAB also help inhibit the growth of disease-causing microbes in our stomachs.

2. Fermentation in Dough:

   • Dough used for dosa and idli undergoes fermentation by bacteria.
   • CO2 gas is produced during fermentation, giving the dough its puffed-up appearance.
   • This fermentation process involves glycolysis, where sugars are broken down to produce energy and CO2.

3. Bread Fermentation:

   • Bread dough undergoes fermentation by baker’s yeast (Saccharomyces cerevisiae).
   • Yeast ferments sugars in the dough, producing CO2 gas, which causes the dough to rise.
   • Baker’s yeast is specifically cultivated for bread-making.

4. Traditional Fermented Foods and Drinks:

   • Examples include toddy (fermented palm sap), fermented fish, soybeans, bamboo shoots, and cheese.
   • Microbes play a crucial role in fermenting these foods and drinks.

5. Specific Microbial Contributions in Cheese-making:

   • Propionibacterium sharmanii contributes to the formation of large holes in Swiss cheese by producing CO2 gas.
   • Fungi used in cheese ripening, such as in Roquefort cheese, impart specific flavors to the cheese.

8.2 MICROBES IN INDUSTRIAL PRODUCTS

1. Beverages Production:

   • Microbes play a vital role in the production of various beverages through fermentation processes.
   • Examples include:
     • Beer: Yeast fermentation converts sugars from barley or other grains into alcohol and carbon dioxide.
     • Wine: Yeast fermentation of grapes converts sugars into alcohol.
     • Spirits: Fermentation followed by distillation produces spirits like whiskey, vodka, and rum.

2. Antibiotics Production:

   • Many antibiotics are produced by microbial fermentation.
   • Examples include:
     • Penicillin: Produced by the fungus Penicillium spp.
     • Streptomycin: Produced by the bacterium Streptomyces griseus.
     • Tetracycline: Produced by various species of Streptomyces.

3. Industrial Scale Production:

   • To produce these products on an industrial scale, microbes are grown in large vessels called fermentors or bioreactors.
   • Fermentors provide optimal conditions for microbial growth and product formation, such as controlled temperature, pH, oxygen supply, and nutrient availability.
   • The scale of production in fermentors allows for the efficient and cost-effective synthesis of beverages, antibiotics, and other microbial products.

8.2.1 Fermented Beverages

1. Fermentation Process:

   • Yeasts, particularly Saccharomyces cerevisiae, are commonly used for fermenting malted cereals and fruit juices to produce ethanol.
   • The process involves the conversion of sugars present in the raw materials into ethanol and carbon dioxide through fermentation.

2. Metabolic Reactions:

   • The primary metabolic pathway involved in the production of ethanol by yeast is alcoholic fermentation.
   • Alcoholic fermentation occurs in the absence of oxygen (anaerobic conditions) and involves the following steps:
     • Glycolysis: This initial step breaks down glucose molecules into two molecules of pyruvate, producing a small amount of ATP (energy) and NADH.
     • Decarboxylation: Pyruvate is then decarboxylated, forming acetaldehyde and releasing carbon dioxide as a byproduct.
     • Reduction: Acetaldehyde is subsequently reduced by NADH to form ethanol, regenerating NAD+ in the process.

3. Types of Alcoholic Beverages:

   • Depending on the raw material used for fermentation and the processing methods, different types of alcoholic beverages are obtained:
     • Wine and Beer: Produced without distillation, these beverages are typically made from fermented fruit juices (wine) or malted cereals (beer).
     • Whisky, Brandy, and Rum: Produced by distillation of the fermented broth, resulting in higher alcohol content and distinct flavors.

4. Fermentation Plant:

   • The photograph of a fermentation plant (Figure 8.5) likely depicts the large-scale industrial setup used for fermenting raw materials to produce alcoholic beverages.
   • These plants utilize fermentors or bioreactors to provide optimal conditions for yeast growth and fermentation, enabling efficient production of ethanol.

8.2.2 Antibiotics 

1. Definition and Significance:

   • Antibiotics are chemical substances produced by certain microbes that can kill or inhibit the growth of other microbes, particularly those that cause diseases.
   • They are considered one of the most significant discoveries of the twentieth century and have greatly contributed to human welfare by enabling the treatment of deadly diseases.

2. Origin and Discovery of Penicillin:

   • Penicillin, the first antibiotic to be discovered, was found by Alexander Fleming in a chance observation.
   • While working with Staphylococci bacteria, Fleming noticed a mould (Penicillium notatum) growing on one of his unwashed culture plates, inhibiting the growth of Staphylococci around it.
   • Fleming identified that the mould was producing a chemical substance, which he named Penicillin.
   • The full potential of Penicillin as an effective antibiotic was established later by Ernest Chain and Howard Florey.
   • Penicillin was extensively used to treat American soldiers wounded in World War II, leading to its widespread adoption and recognition.
   • Fleming, Chain, and Florey were awarded the Nobel Prize in 1945 for their discovery of Penicillin.

3. Other Antibiotics and their Sources:

   • Other antibiotics have been purified from various microbes:
     • Streptomycin: Produced by the bacterium Streptomyces griseus.
     • Tetracycline: Produced by various species of Streptomyces.
     • Erythromycin: Produced by the bacterium Saccharopolyspora erythraea.
     • Vancomycin: Produced by the bacterium Amycolatopsis orientalis.
     • Cephalosporins: Derived from fungi in the genus Cephalosporium.

4. Impact on Disease Treatment:

   • Antibiotics have revolutionized the treatment of deadly diseases such as plague, whooping cough, diphtheria, and leprosy, which previously caused millions of deaths worldwide.
   • They have become indispensable in modern medicine, and the development of antibiotic resistance highlights the ongoing need for responsible antibiotic use and continued research into new antibiotics.

8.2.3 Chemicals, Enzymes and other Bioactive Molecules

1. Production of Chemicals:

   • Microbes are utilized for the commercial production of various chemicals, including organic acids, alcohols, and enzymes.
   • Examples of acid producers include:
     • Aspergillus niger: Produces citric acid.
     • Acetobacter aceti: Produces acetic acid.
     • Clostridium butylicum: Produces butyric acid.
     • Lactobacillus: Produces lactic acid.
   • Yeast (Saccharomyces cerevisiae) is used for the commercial production of ethanol.

2. Production of Enzymes:

   • Microbes are employed in the production of enzymes used in various industrial applications.
   • Examples include:
     • Lipases: Used in detergent formulations to remove oily stains from laundry.
     • Pectinases and proteases: Used to clarify bottled fruit juices, resulting in clearer juices compared to homemade ones.

3. Bioactive Molecules:

   • Microbes also produce bioactive molecules with therapeutic applications:
     • Streptokinase: Produced by the bacterium Streptococcus and used as a “clot buster” to remove clots from the blood vessels of patients who have had a heart attack.
     • Cyclosporin A: Produced by the fungus Trichoderma polysporum and used as an immunosuppressive agent in organ transplant patients.
     • Statins: Produced by the yeast Monascus purpureus and used as blood-cholesterol lowering agents by competitively inhibiting the enzyme responsible for cholesterol synthesis.

8.3 MICROBES IN SEWAGE TREATMENT

1. Generation and Disposal of Sewage:

   • Large quantities of wastewater, including human excreta, are generated daily in cities and towns, constituting municipal waste-water or sewage.
   • Sewage contains significant amounts of organic matter and pathogenic microbes, making direct discharge into natural water bodies unsafe.

2. Sewage Treatment Plants (STPs):

   • Sewage is treated in STPs to reduce its pollutant content before disposal.
   • Treatment is primarily carried out by heterotrophic microbes naturally present in sewage.

3. Primary Treatment:

   • Involves physical removal of particles (both large and small) from sewage through filtration and sedimentation.
   • Sequential filtration removes floating debris, followed by sedimentation to remove grit (soil and small pebbles), forming primary sludge and effluent.

4. Secondary Treatment or Biological Treatment:

   • Primary effluent is subjected to biological treatment in large aeration tanks.
   • Constant mechanical agitation and aeration promote the growth of aerobic microbes into flocs, which consume organic matter, reducing biochemical oxygen demand (BOD).
   • BOD is a measure of the organic matter present in water and indicates its polluting potential.
   • Effluent is treated until BOD is significantly reduced, then passed into a settling tank where bacterial flocs sediment, forming activated sludge.
   • Some activated sludge is recycled as inoculum, while the majority is digested by anaerobic bacteria in anaerobic sludge digesters, producing biogas (methane, hydrogen sulphide, carbon dioxide).

5. Discharge of Treated Effluent:

   • Treated effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.
   • Microbial treatment of sewage has been practiced globally for over a century and remains unmatched by man-made technologies.

6. Challenges and Initiatives:

   • Increasing urbanization has led to a surge in sewage production, outpacing the capacity of existing treatment plants.
   • Untreated sewage discharge into rivers contributes to pollution and waterborne diseases.
   • Initiatives like the Ganga Action Plan and Yamuna Action Plan aim to build more sewage treatment plants to mitigate river pollution.

7. Educational Opportunities:

   • Visiting a sewage treatment plant can provide valuable insights into wastewater treatment processes and the role of microbes.