Microbes in Human Welfare

INTRODUCTION TO MICROBES

This chapter Microbes in Human Welfare, focuses on the diverse roles of microbes in various fields, including household products, industrial applications, sewage treatment, biogas production, biocontrol, and biofertilizers.

• Definition
  • Microorganisms (Microbes) are organisms that:
    • Cannot be seen with the naked eye
    • Are observed under a microscope
  • They are major components of biological systems on Earth.

Where are Microbes Found?

• Ubiquitous Nature: Microbes are present everywhere:
  • Soil
  • Water
  • Air
  • Inside human body
  • Inside animals
  • Inside plants
• Extreme Habitats: Microbes can survive in extreme conditions such as:
  • Hot geysers (up to ~100°C)
  • Deep ocean vents
  • Snow layers
  • Highly acidic environments

Types of Microbes

Microbes include diverse biological groups:

• Bacteria
• Fungi
• Protozoa
• Microscopic algae
• Viruses
• Viroids
• Prions (proteinaceous infectious agents)

Important Feature

• Many bacteria and fungi:
  • Can be grown on culture media
  • Form visible colonies in petri dishes
• Culturing helps in:
  • Research
  • Industrial applications

Importance of Microbes

• Not all microbes are harmful.
• Many are essential in:
  • Food production
  • Industry
  • Medicine
  • Agriculture
  • Environmental management

Microbes in Household Products

• Microbes are involved in daily-use products such as:
  • Curd
  • Yogurt
  • Bread
  • Cheese
  • Traditional fermented foods

A. MAKING OF CURD

• Microbes involved:
  • Lactobacillus
  • Other Lactic Acid Bacteria (LAB)

• Process (Stepwise Mechanism)
  1. A small amount of curd (starter) is added to milk.
  2. LAB multiply at suitable temperature.
  3. Lactose is converted into lactic acid.
  4. Lactic acid coagulates milk protein (casein).
  5. Milk converts into curd.

• Benefits
  • Improves digestibility
  • Increases Vitamin B12 content
  • Maintains healthy gut flora
  • Suppresses harmful microbes in stomach

Other Dairy Applications

• Yogurt
  • Microbes: Streptococcus thermophilus
  • Lactobacillus bulgaricus
• Butter
  • Produced by churning cream fermented by LAB
• Buttermilk
  • Produced using Lactobacillus species

B. CHEESE PRODUCTION

• Basic Principle
  • Curd is separated from whey.
  • Concentrated milk fat + casein forms cheese.
• Types Based on Water Content
  • Soft cheese → 50–80% water
  • Semi-hard cheese → ~45% water
  • Hard cheese → <40% water
• Ripening Process
  • Involves bacteria and fungi
  • Maturation period: 1–16 months

Special Examples

• Swiss Cheese
  • Large holes due to CO₂ production
  • Microbe: Propionibacterium shermanii
• Roquefort Cheese
  • Ripened by Penicillium roqueforti
• Camembert Cheese
  • Ripened by Penicillium camemberti

Key Concept – CO₂ production during fermentation creates holes and texture in cheese.

C. FERMENTED DOUGH PRODUCTS

• Foods:
  • Idli
  • Dosa
  • Bread
• Mechanism
  1. Bacteria ferment carbohydrates.
  2. CO₂ is produced.
  3. Dough becomes soft and puffed.
• Bread Fermentation
  • Microbe: Baker’s yeast
  • Scientific name: Saccharomyces cerevisiae
• Result
  • Soft texture
  • Enhanced flavor
  • Improved digestibility

D. TRADITIONAL FERMENTED FOODS & DRINKS

• Toddy:
  • Fermented palm sap
  • Traditional drink in southern India
• Other fermented foods:
  • Fish
  • Soybean
  • Bamboo shoots

• Fermentation Improves
  • Shelf life
  • Flavor
  • Nutritional value

INDUSTRIAL USE OF MICROBES

Introduction

• Microbes are widely used in industries to produce products beneficial to humans.
• Large-scale industrial production is carried out in special vessels called:
  • Fermentors

Role of Fermentors

• Fermentors provide controlled conditions for:
  • Temperature
  • pH
  • Aeration
  • Nutrient supply
  • Sterility
• These controlled parameters ensure maximum yield and product purity.

Fermented Beverages

• Basic Principle
  • Yeast converts sugars into:
    • Ethanol + Carbon dioxide
• General Reaction
  • Glucose → Ethanol + CO₂
• Main Microbe Used
  • Saccharomyces cerevisiae
  • Also called: Brewer’s yeast
• Other Yeast Strains Used
  • Saccharomyces ellipsoideus → Wine yeast
  • Saccharomyces sake → Sake yeast
  • Saccharomyces piriformis → Ginger beer yeast

TYPES OF ALCOHOLIC BEVERAGES

• A. Undistilled Beverages (Low Alcohol Percentage)
  • Wine
  • Beer
• B. Distilled Beverages (High Alcohol Percentage / Hard Liquor)
  • Whisky
  • Brandy
  • Rum
  • Gin
  • Vodka
  • Fenny
  • Arrack

Key Concept: Distillation increases alcohol concentration.

RAW MATERIALS USED

• Barley malt → Beer
• Fermented fruit juice → Wine and Brandy
• Fermented molasses → Rum
• Fermented corn/rye → Whisky
• Rice → Sake
• Potato → Vodka

Antibiotics

• Definition:
  • Antibiotics are chemical substances produced by microbes that:
    • Kill other microorganisms OR Inhibit their growth
• Word Meaning:
  • Anti → Against
  • Bio → Life
  • In medical context → Substance against disease-causing organisms

DISCOVERY OF PENICILLIN

• First antibiotic: Penicillin.
• Discovery:
  • 1928 – Discovered accidentally by Alexander Fleming
  • Observed mould inhibiting Staphylococci bacteria
  • Mould identified as Penicillium notatum
• Development for Commercial Use:
  • Ernst Chain
  • Howard Florey
• Recognition:
  • Nobel Prize – 1945
    Awarded to: Fleming, Chain, Florey
• Historical Importance:
  • Extensively used during World War II
  • Saved thousands of soldiers

Impact of Antibiotics

Antibiotics revolutionized modern medicine.

• Effective against:
  • Plague
  • Whooping cough
  • Diphtheria
  • Leprosy
  • Tuberculosis
  • Pneumonia
• Modern healthcare is unimaginable without antibiotics.

CHEMICALS, ENZYMES & BIOACTIVE MOLECULES

• Microbes function as industrial biofactories.
• They synthesize at commercial scale:
  • Organic acids
  • Alcohols
  • Enzymes
  • Medically important bioactive molecules

1. ORGANIC ACIDS (Microbial Fermentation Products)

A. Citric Acid

• Produced by: Aspergillus niger (fungus).
• Industrial substrate: Molasses (cane/beet sugar)
• Uses
  • Food preservative
  • Flavoring agent
  • Medicines
  • Dyeing industry
• Important Fact
  • One of the earliest large-scale microbial fermentation products.

B. Acetic Acid

• Produced by: Acetobacter aceti (bacterium).
• Source: Oxidation of fermented alcohol
• Uses
  • Vinegar preparation
  • Pharmaceuticals
  • Insecticides
  • Plastics

C. Lactic Acid

• Produced by: Lactobacillus bulgaricus and related species (bacterium).
• Raw materials:
  • Corn starch
  • Molasses
  • Whey
• Uses
  • Food preservation
  • Curd formation
  • Pharmaceutical formulations
• Historical Note
  • First organic acid produced via microbial fermentation (1789).

D. Butyric Acid

• Produced by: Clostridium acetobutylicum (bacterium).
• Associated with rancid butter odor.

2. ALCOHOL PRODUCTION

• Ethanol:
  • Produced by: Saccharomyces cerevisiae (Yeast).
• Process
  • Fermentation of sugars → Ethanol + CO₂
• Applications
  • Alcoholic beverages
  • Industrial solvent
  • Biofuel

3. INDUSTRIAL ENZYMES

Microbes produce enzymes widely used in detergents, food and medicine.

A. Lipases

• Source: Yeasts such as Candida species
• Use
  • Removal of oily stains in detergents

B. Pectinases & Proteases

• Source: Fungal species
• Use
  • Clarification of fruit juices
  • Improve juice clarity
  • Enhance shelf life

4. BIOACTIVE MOLECULES (Medical Importance)

A. Streptokinase

• Produced by: Streptococcus
• Function
  • Dissolves blood clots
  • Used in myocardial infarction (heart attack)
• Also called: Clot buster
• Mechanism
  • Converts plasminogen → Plasmin
  • Plasmin dissolves fibrin clot.

B. Cyclosporin A

• Produced by: Trichoderma polysporum (fungus).
• Nature: Cyclic peptide
• Function
  • Immunosuppressant
  • Prevents graft rejection in organ transplantation

C. Statins

• Produced by: Monascus purpureus (yeast)
• Function
  • Lower blood cholesterol
• Mechanism
  • Inhibits HMG-CoA reductase
  • (HMG-CoA reductase is involved in cholesterol synthesis pathway.)
• Medical Importance
  • Prevention of heart diseases

Microbes in Sewage Treatment

What is Sewage?

• Sewage is municipal wastewater containing:
  • Human excreta
  • Organic waste
  • Pathogenic microbes
  • Suspended solids
• Problem of Direct Discharge
  • Water pollution
  • Water-borne diseases
  • Oxygen depletion
• Solution
  • Treatment in Sewage Treatment Plants (STPs)

STAGES OF SEWAGE TREATMENT

• Main stages:
  1. Primary Treatment (Physical)
  2. Secondary Treatment (Biological)
  3. Tertiary Treatment (Advanced; optional)

Primary Treatment

• Purpose:
  • Removal of floating and suspended solids
• Steps:
  1. Screening: Removes large debris
  2. Grit Chamber: Sand and pebbles settle
  3. Sedimentation Tank: Suspended particles settle
• Outputs:
  • Primary sludge → Settled solids at the bottom.
  • Effluent → Supernatant liquid (Primary sludge)
    • Primary sludge → Sent for composting/processing (secondary treatment process)

Secondary Treatment (Biological Treatment)

Also called: Activated Sludge Process

Step 1: Aeration Tank

• Effluent pumped into aeration tank
• Continuous air supply agitated (mixed).
• Aerobic microbes grow vigorously
• Microbes form flocs
  • Flocs = Mesh-like aggregates of bacteria + fungal filaments

Step 2: BOD Reduction

• Definition
  • Biochemical Oxygen Demand (BOD) = Amount of oxygen required by microbes to oxidize organic matter in 1 litre of water
• Microbial digestion reduces BOD to: 10–15% of original level

Step 3: Settling Tank

• Flocs settle → Activated sludge
• Small portion → Returned to aeration tank as inoculum
• Remaining sludge → Sent to anaerobic digester (large tanks).

ANAEROBIC SLUDGE DIGESTER

• Anaerobic bacteria digest sludge
• Produce biogas

Composition of Biogas

• Methane (CH₄)
• Carbon dioxide (CO₂)
• Hydrogen sulphide (H₂S)

• Uses
  • Energy source

Final effluent (low BOD) → Released into rivers

Importance of Sewage Treatment

• Prevents river pollution
• Reduces water-borne diseases
• Generates biogas
• Essential due to urbanization

Government Initiatives (India)

1. Ganga Action Plan
2. Yamuna Action Plan

• Launched under National River Conservation Authority
• Purpose:
  • Build STPs
  • Reduce river pollution

Microbes have been used in sewage treatment for over a century, and no man-made technology has matched their efficiency.

Microbes in Production of Biogas

• What is Biogas?
  • Biogas is a methane-rich fuel produced by microbial degradation of organic matter under anaerobic (oxygen-free) conditions.
• Composition of Biogas
  • 50–70% Methane (CH₄)
  • 30–40% Carbon dioxide (CO₂)
  • 1–5% Hydrogen (H₂)
  • Traces of H₂S, N₂, O₂
• Key Concept:
  • Methane (CH₄) is the main combustible component.

METHANOGENS

• Definition
  • Methanogens are anaerobic bacteria that produce methane from cellulosic material.
• Examples
  • Methanobacterium
  • Methanococcus

Where Are Methanogens Found?

• Anaerobic sludge (during sewage treatment)
• Rumen of cattle (first stomach chamber)
• Cattle dung (gobar)

Role in Rumen

• Methanogens help break down cellulose present in cattle food.
• Result:
  • Improved digestion
  • Better nutrition in cattle

BIOGAS PRODUCTION PROCESS

Structure of a Biogas Plant

1. Digester (Concrete Tank)
   • 10–15 feet deep
   • Contains dung slurry (cattle dung + water)
2. Floating Gas Holder
   • Rises as gas accumulates
   • Stores produced biogas
3. Gas Outlet Pipe
   • Supplies gas to houses
4. Supplies gas to houses
   • Removes spent slurry
   • Spent slurry used as manure

STAGES OF BIOGAS FORMATION

1. Solubilisation
   • Complex organic matter → Simple monomers
2. Acidogenesis
   • Monomers → Organic acids
3. Methanogenesis
   • Organic acids → Methane + CO₂ + H₂

Optimal Temperature

• 34–48°C

Gas Flow Mechanism

• Gas formation increases pressure inside digester.
• Floating dome rises.
• Gas is supplied to homes through outlet pipe.

Uses of Biogas

• Cooking fuel
• Lighting in rural areas
• Renewable energy source
• Slurry used as organic fertilizer

Key Concept: Biogas is eco-friendly and reduces dependency on fossil fuels.

Development of Biogas Technology in India

• Biogas technology promoted by:
  • Indian Agricultural Research Institute (IARI)
  • Khadi and Village Industries Commission (KVIC)
• Common name: Gobar Gas Plant

Microbes as Biocontrol Agents

• What is Biocontrol?
  • Biocontrol is the use of biological organisms to control plant diseases and pests instead of chemical pesticides.

WHY BIOCONTROL IS NEEDED

• Problems with Chemical Pesticides:
  • Toxic to humans and animals
  • Pollute soil and groundwater
  • Kill beneficial insects
  • Disturb ecological balance
• Biocontrol provides a safer alternative.

Benefits of Biocontrol

• Biodegradable
• Non-persistent
• Maintains biodiversity
• Keeps pests at manageable level
• Reduces environmental pollution

Holistic approach: Works through food chains and ecological interactions.

Examples of Biocontrol Agents

• Natural Predators
  • Ladybird beetle (Coccinella) → Controls aphids
  • Dragonflies (Sympetrum) → Control mosquitoes

Bacterial Bioinsecticide

• Bacillus thuringiensis (Bt)
  • Produces: Cry protein toxin
• Mechanism
  • Ingested by caterpillar larvae
  • Toxin activated in alkaline midgut
  • Creates pores in gut epithelial cells
  • Larvae die
• Available Forms
  • Spore formulation (spray)
  • Bt-transgenic crops (e.g., Bt cotton)
• Effective mainly against Lepidopteran larvae.

Fungal Biocontrol Agents

• Trichoderma
  • Free-living soil fungus
  • Controls several plant pathogens
  • Used in seed treatment and soil application
• Beauveria bassiana
  • Controls insect pests

Viral Biocontrol

• Baculoviruses, Especially: Nucleopolyhedrovirus
  • Species-specific
  • Narrow spectrum insecticide
  • No harm to plants, mammals, birds, fish
• Safe for non-target organisms.

Bioherbicide Example: Phytophthora palmivora

• Controls milkweed in citrus orchards

INTEGRATED PEST MANAGEMENT (IPM)

• IPM combines:
  • Biological control
  • Cultural practices
  • Limited chemical use
  • Crop rotation
  • Sanitation
• Goal: Sustainable agriculture + Environmental protection

ENVIRONMENTAL CONCERN

• Excessive use of chemical fertilizers has resulted in:
  • Water body pollution
  • Groundwater contamination
  • Soil degradation
  • Chemical accumulation in crops

• Solution
  • Shift towards:
    • Organic farming
    • Biofertilisers

ORGANIC FARMING

• Crop production using biological inputs such as:
  • Manures
  • Biofertilisers
  • Biopesticides
  • Crop rotation
  • Intercropping
• Goal: Sustainable agriculture with minimal environmental damage.

Microbes as Biofertilisers

• Definition
  • Biofertilisers are living organisms that enhance soil nutrient quality by increasing availability of essential nutrients such as:
    • Nitrogen
    • Phosphorus
• Main Groups
  • Bacteria
  • Fungi
  • Cyanobacteria

BACTERIA AS BIOFERTILISERS

1. Symbiotic Nitrogen-Fixing Bacteria

• Example: Rhizobium
• Association
  • Lives inside root nodules of leguminous plants
  • Mutualistic (symbiotic) relationship
• Function
  • Fixes atmospheric nitrogen (N₂)
  • Converts N₂ → Organic nitrogen compounds usable by plants
• Nutritional Exchange
  • Plant provides carbohydrates
  • Bacteria provide nitrogen

2. Free-Living Nitrogen-Fixing Bacteria

• Example: Azotobacter & Azospirillum
• Characteristics
  • Live freely in soil
  • Fix atmospheric nitrogen independently
  • Enrich soil nitrogen content
• Other Free-Living Examples (Exam Awareness)
  • Clostridium
  • Rhodospirillum

FUNGI AS BIOFERTILISERS (MYCORRHIZA)

• Definition
  • Mycorrhiza = Symbiotic association between fungi and plant roots
• Common Fungal Partner
  • Glomus

FUNCTIONS OF MYCORRHIZA

• Enhances phosphorus absorption
• Improves water uptake
• Increases root surface area
• Protects against root pathogens
• Improves tolerance to salinity
• Improves tolerance to drought
• Enhances overall plant growth

TYPES OF MYCORRHIZA

1. Ectomycorrhiza
   • Fungus grows in intercellular spaces of root cortex
   • Hyphae form external sheath
   • Increase root surface area
2. Endomycorrhiza
   • Also called: VAM (Vesicular Arbuscular Mycorrhiza)
     • Hyphae penetrate cortical cells
     • Form vesicles and arbuscules
     • Supply inorganic nutrients efficiently
   • Exam Differentiator
     • VAM greatly increases phosphate availability.

Exam Differentiator – VAM greatly increases phosphate availability.

CYANOBACTERIA AS BIOFERTILISERS

• Definition
  • Cyanobacteria are photosynthetic nitrogen-fixing microbes.
• Examples
  • Anabaena
  • Nostoc
  • Oscillatoria

Role in Paddy Fields

• Fix atmospheric nitrogen
• Add organic matter to soil
• Improve soil fertility
• Act as low-cost biofertiliser

Important Fact – Extremely useful in rice cultivation.

• Special Mention: Aulosira fertilissima
  • Very active nitrogen fixer
  • Used in Indian rice fields

CLASSIFICATION SUMMARY

• Free-Living Nitrogen Fixers
  • Azotobacter
  • Azospirillum
• Symbiotic Nitrogen Fixers
  • Rhizobium
• Fungal Biofertilisers
  • Glomus (Mycorrhiza)
• Cyanobacterial Biofertilisers
  • Anabaena
  • Nostoc

IMPORTANCE OF BIOFERTILISERS

• Increase crop yield (15–35%)
• Improve soil texture
• Reduce dependency on chemical fertilizers
• Non-polluting
• Promote sustainable agriculture
• Effective in semi-arid regions
• Produce growth-promoting substances

CURRENT STATUS IN INDIA

• Commercially available
• Widely used in organic farming
• Reduce environmental pollution
• Encourage sustainable agriculture

Chapter Summary

CORE IDEA

• Microbes are indispensable for life on Earth.
• Although some cause diseases, a vast majority are beneficial and support human welfare in multiple ways.

MICROBES IN HOUSEHOLD PRODUCTS

• Lactic Acid Bacteria (LAB) convert milk into curd by producing lactic acid.
• Saccharomyces cerevisiae ferments dough → bread making.
• Fermentation makes idli and dosa soft and fluffy (CO₂ production).
• Specific bacteria and fungi give cheese its texture, flavor and aroma.

MICROBES IN INDUSTRIAL PRODUCTS

• Organic acids produced by microbes:
  • Lactic acid
  • Acetic acid
  • Citric acid
• Alcohol (ethanol) produced by yeast fermentation.
• Antibiotics are microbial products that kill harmful pathogens.
• Example:
  • Penicillin discovered from Penicillium notatum
  • Controls diseases like diphtheria, whooping cough, pneumonia, etc.
• Antibiotics revolutionized modern medicine.

MICROBES IN SEWAGE TREATMENT

• For more than 100 years, microbes have been used to treat sewage.
• In the activated sludge process, aerobic microbes form flocs.
• These microbes reduce Biochemical Oxygen Demand (BOD).
• Anaerobic bacteria digest sludge and produce biogas.
• This process reduces pollution and protects water bodies.

MICROBES IN BIOGAS PRODUCTION

• Methanogens such as Methanobacterium produce methane.
• Biogas contains mainly methane and carbon dioxide.
• Produced from cattle dung and plant waste.
• Used as cooking fuel and rural energy source.
• Eco-friendly and renewable.

MICROBES AS BIOCONTROL AGENTS

• Biocontrol = Use of biological agents to control pests.
• Reduces dependency on toxic chemical pesticides.
• Example:
  • Bacillus thuringiensis (Bt) produces toxin that kills caterpillars.
  • Helps maintain ecological balance.
• Biocontrol supports sustainable agriculture.

MICROBES AS BIOFERTILISERS

• Chemical fertilizers cause environmental pollution.
• Biofertilisers are eco-friendly alternatives.
• Examples:
  • Rhizobium → Nitrogen fixation in legumes.
  • Glomus → Improves phosphate absorption.
  • Cyanobacteria in paddy fields fix atmospheric nitrogen.
• They improve soil fertility and crop yield sustainably.

OVERALL IMPORTANCE

• Microbes:
  • Support food production
  • Produce medicines
  • Treat waste
  • Generate renewable energy
  • Protect crops
  • Improve soil fertility
• Conclusion:
  • Microbes are fundamental to human society’s welfare and sustainable development.