Microbes in Industrial and Household Products

Microbes in household and industrial products range from the lactic acid bacteria that set curd to the yeast that raises bread and brews beer. This page covers where microbes live, curd, dough, toddy and cheese, fermentors and alcoholic beverages, the discovery of penicillin, and the acids, enzymes and drugs that microbes make, as in the NCERT Class 12 chapter Microbes in Human Welfare. NEET often asks microbe and product pairs, so learn every name in the tables on microbes in household and industrial products.

1. Microbes Around Us

• Microbes (micro-organisms): tiny forms of life, most of which can be seen only under a microscope.
• Besides large (macroscopic) plants and animals, microbes are major components of the biological systems on earth.
• Microbes occur everywhere: in soil, water and air, and inside the bodies of humans, other animals and plants.
• ★ Exam imp They live even at sites where no other life form could possibly exist.

1.1 Diversity of microbes

• Microbes are diverse: protozoa, bacteria, fungi, microscopic animal and plant viruses, viroids and prions.
• Prions: proteinaceous infectious agents, that is, infectious agents made of protein.
• Bacteria come in different shapes, such as rod-shaped and spherical forms.

• Bacteria and many fungi can be grown on nutritive media (media that supply nutrients) to form colonies.
• A colony is large enough to be seen with the naked eye.
• Such cultures are useful in studies on micro-organisms.

• Microbes cause a large number of diseases in human beings, animals and plants.
• ★ Exam imp Yet not all microbes are harmful; several are useful to humans in diverse ways.

2. Microbes in Household Products

• We use microbes, or products made from them, every day.

2.1 Curd from milk

• ★ Exam imp Lactic acid bacteria (LAB): Lactobacillus and other bacteria that grow in milk and convert it to curd.

1. A small amount of curd is added to fresh milk as an inoculum or starter; it carries millions of LAB.
2. At a suitable temperature, the LAB multiply in the milk.
3. While growing, the LAB produce acids.
4. The acids coagulate (set) and partially digest the milk proteins, so the milk turns into curd.

• ★ Exam imp Curd is more nutritious than milk, because LAB increase its vitamin ${\mathrm{B}}_{12}$.
• In our stomach too, LAB play a very useful role: they check disease-causing microbes.

2.2 Fermented dough

• The dough used for dosa and idli is fermented by bacteria.
• The puffed-up appearance of the dough is due to the production of $\mathrm{C}{\mathrm{O}}_2$ gas.
• The dough used for bread is fermented by baker's yeast, Saccharomyces cerevisiae.

2.3 Traditional foods and drinks

• Many traditional drinks and foods are made by microbial fermentation.
• Toddy: a traditional drink of some parts of southern India, made by fermenting the sap of palms.
• Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods.

2.4 Cheese

• Cheese is one of the oldest foods in which microbes were used.
• Varieties of cheese differ in texture, flavour and taste; each variety owes this to the microbes used.
• ★ Exam imp Swiss cheese: its large holes come from a large amount of $\mathrm{C}{\mathrm{O}}_2$ made by the bacterium Propionibacterium sharmanii (also spelt shermanii).
• Roquefort cheese: ripened by growing a specific fungus on it, which gives it a particular flavour.

3. Fermentors and Fermented Beverages

• In industry, microbes make many products of value to human beings; beverages and antibiotics are examples.

3.1 Fermented beverages

• Microbes, especially yeasts, have been used since time immemorial to make wine, beer, whisky, brandy and rum.
• ★ Exam imp The yeast is the same Saccharomyces cerevisiae used for bread; in brewing it is called brewer's yeast.
• It ferments malted cereals and fruit juices to produce ethanol.
• The kind of drink depends on the raw material and on the processing: with or without distillation.

4. Antibiotics

• Antibiotics made by microbes are among the most significant discoveries of the twentieth century.
• They have contributed greatly to the welfare of human society.
• Anti is a Greek word for 'against', and bio means 'life'; together, 'against life'.
• Here 'life' means disease-causing organisms. For human beings, antibiotics are 'pro life', not against life.

4.1 Discovery of penicillin

• ★ Exam imp Penicillin was the first antibiotic to be discovered, and it was a chance discovery.

1. Alexander Fleming was working on Staphylococci bacteria.
2. He saw a mould growing in one of his unwashed culture plates; Staphylococci could not grow around it.
3. He found that a chemical produced by the mould caused this.
4. He named the chemical Penicillin, after the mould Penicillium notatum.
5. Later, Ernest Chain and Howard Florey established its full potential as an effective antibiotic.
6. Penicillin was used extensively to treat American soldiers wounded in World War II.
7. Fleming, Chain and Florey were awarded the Nobel Prize in 1945 for this discovery.

4.2 Impact of antibiotics

• After penicillin, other antibiotics were purified from other microbes.
• Antibiotics greatly improved the treatment of deadly diseases that once killed millions across the globe.
• Examples: plague, whooping cough, diphtheria and leprosy; antibiotics also helped control pneumonia.
• Today, we cannot imagine a world without antibiotics.

5. Chemicals, Enzymes and Other Bioactive Molecules

• Microbes are used for the commercial and industrial production of organic acids, alcohols and enzymes.

5.1 Organic acids and alcohol

5.2 Enzymes

• Lipases: used in detergent formulations; they help remove oily stains from laundry.
• Bottled fruit juices are clearer than home-made ones, because they are clarified by pectinases and proteases.
• ★ Exam imp Streptokinase: made by the bacterium Streptococcus and modified by genetic engineering; used as a 'clot buster'.
• It removes clots from the blood vessels of patients who have had a myocardial infarction, which leads to heart attack.
• Myocardial infarction: damage to the heart muscle caused by a blocked blood supply.

5.3 Bioactive molecules

• Cyclosporin A: an immunosuppressive agent (it suppresses the immune response) used in organ-transplant patients.
• Cyclosporin A is produced by the fungus Trichoderma polysporum.
• Statins: produced by the yeast Monascus purpureus; commercialised as blood-cholesterol lowering agents.
• Statins act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

6. Exam Essentials

Pairs to Match

Numbers to Remember

• $100{}^{\circ }\mathrm{C}$: temperature deep inside geysers (thermal vents), where microbes still live.
• 1500 times: magnification of the rod-shaped and spherical bacteria in Figure 1.
• 50,000 times: magnification of the flagellated bacterium in Figure 2.
• 1,00,000 to 1,50,000 times: magnification of the viruses in Figure 3.
• Twentieth century: antibiotics rank among its most significant discoveries.
• World War II: penicillin treated wounded American soldiers.
• 1945: Nobel Prize to Fleming, Chain and Florey.

Examples to Remember

7. Quick Revision

• Microbes live everywhere, even in geysers at $100{}^{\circ }\mathrm{C}$, deep soil, under thick snow and in acidic sites.
• Microbes include protozoa, bacteria, fungi, viruses, viroids and prions (proteinaceous infectious agents).
• Bacteria and many fungi form colonies on nutritive media that are visible to the naked eye.
• LAB such as Lactobacillus make curd; their acids coagulate milk proteins; vitamin ${\mathrm{B}}_{12}$ rises.
• Dosa and idli dough: bacteria; bread dough: baker's yeast; $\mathrm{C}{\mathrm{O}}_2$ puffs up the dough.
• Toddy: fermented palm sap; fish, soyabean and bamboo shoots are also fermented.
• Swiss cheese holes: $\mathrm{C}{\mathrm{O}}_2$ from Propionibacterium sharmanii; Roquefort: ripened by a fungus.
• Fermentors are very large vessels for industrial-scale growth of microbes.
• Brewer's yeast is S. cerevisiae; wine and beer are not distilled; whisky, brandy and rum are.
• Antibiotics kill or retard disease-causing microbes; penicillin was the first, a chance discovery by Fleming.
• Chain and Florey established penicillin's value; Nobel Prize 1945 to all three.
• Acids: Aspergillus niger (citric), Acetobacter aceti (acetic), Clostridium butylicum (butyric), Lactobacillus (lactic).
• Lipases in detergents; pectinases and proteases clarify juices; streptokinase is a clot buster.
• Cyclosporin A (Trichoderma polysporum) is an immunosuppressant; statins (Monascus purpureus) lower cholesterol.

8. Solved Examples

Common Mistakes to Avoid