Microbes in Human Welfare: Class 12 NCERT Biology Explained

Microbes in Household Food Products

Microbes are essential in preparing many household foods, especially fermented products. For example:

• Curd: Lactic acid bacteria (LAB) like Lactobacillus ferment lactose in milk to produce lactic acid. This acid coagulates milk proteins, improving texture and increasing vitamin B12.
• Dosa and Idli: Fermentation by bacteria and yeast produces carbon dioxide, puffing up the batter.
• Bread: Baker’s yeast (Saccharomyces cerevisiae) ferments sugars, releasing CO2 that makes the dough rise.

These microbes not only enhance taste and texture but also improve nutritional value and preserve food naturally. The starter culture in curd contains millions of LAB that multiply under suitable temperatures to ferment fresh milk.

Activity: Observe curd fermentation by keeping milk at room temperature with a small amount of curd as inoculum. Notice the change in texture and smell after a few hours.

Understanding these microbial processes helps Class 12 students grasp the practical applications of microbes in daily life, as outlined in the NCERT syllabus.

Microbial Roles in Industrial Products and Medicine

Microbes contribute significantly to industries and healthcare:

• Antibiotics Production: Penicillium fungi produce penicillin, the first antibiotic discovered. Other microbes produce streptomycin, tetracycline, and chloramphenicol.
• Vitamins: Certain bacteria synthesize vitamins like B12, essential for human health.
• Enzymes: Microbial enzymes are used in detergents, food processing, and pharmaceuticals.
• Vaccines: Attenuated microbes help develop vaccines that protect against diseases.

In industry, microbes are cultured on a large scale to produce these valuable products. For example, fermenters maintain optimal conditions for microbial growth and product formation.

Worked Example: If a fermenter produces 500 g of penicillin per day with a microbial culture efficiency of 80%, the theoretical maximum production is:

$$\text{Maximum production} = \frac{500}{0.8} = 625 \text{ g/day}$$

This shows the importance of optimizing microbial growth conditions for maximum yield.

This section aligns with the Class 12 NCERT chapter on microbial applications in human welfare.

Microbes in Environmental Management

Microbes play vital roles in maintaining environmental balance:

• Biogas Production: Methanogenic bacteria decompose organic waste anaerobically to produce methane-rich biogas, a renewable energy source.
• Biofertilizers: Nitrogen-fixing bacteria like Rhizobium enrich soil nitrogen, reducing chemical fertilizer use.
• Waste Management: Microbes degrade sewage and industrial waste, helping in bioremediation.

These microbial processes support sustainable agriculture and energy production, which are important topics in Class 12 NCERT Biology.

Understanding these microbial functions encourages students to appreciate microbes beyond disease-causing agents.

Traditional Indian Foods and Microbial Fermentation

Many traditional Indian foods rely on microbial fermentation:

• Idli and Dosa: Made from fermented rice and urad dal batter. Fermentation produces CO2, giving softness and flavor.
• Dhokla: Fermented Bengal gram batter creates a spongy texture.
• Toddy: A traditional fermented drink from palm sap.

These foods benefit from microbes that improve digestibility, taste, and shelf life. The natural microbial flora or starter cultures initiate fermentation.

Comparison of Fermented Foods:

This knowledge supports Class 12 students in understanding microbial diversity and their cultural importance.

Microbes and Human Health: Probiotics and Antibiotics

Microbes influence human health positively through:

• Probiotics: Beneficial bacteria like Lactobacillus and Bifidobacterium improve gut health by inhibiting harmful microbes.
• Antibiotics: Microbes produce substances that kill or inhibit pathogens, revolutionizing medicine.
• Vitamin Production: Gut microbes synthesize vitamins such as vitamin K and some B vitamins.

Regular consumption of fermented foods containing probiotics supports digestion and immunity. Antibiotics derived from microbes have saved millions of lives by treating bacterial infections.

Formula for Antibiotic Effectiveness:

$$\text{Effectiveness} = \frac{\text{Zone of inhibition diameter (mm)}}{\text{Concentration of antibiotic (mg/ml)}}$$

This helps in evaluating antibiotic potency in laboratory tests.

Class 12 NCERT Biology emphasizes these microbial roles to highlight their importance beyond disease.