- Bread is prepared from cereal flour using baker’s yeast (Saccharomyces cerevisiae).
- Yeast ferments carbohydrates to produce carbon dioxide and ethanol.
- Carbon dioxide causes dough to rise, making bread soft and spongy.
- Compressed yeast is used in commercial bakeries, while dry granular yeast is used domestically.
- Yeast is rich in proteins, vitamins, minerals, fats, and carbohydrates, increasing the nutritive value of bread.
Definitions [6]
Definition: Applied Microbiology
Branch of biology in which study of the enzymes related to some prokaryotes and eukaryotic microbes, proteins, applied genetics, molecular biology, etc. is performed; is called as applied microbiology.
Definition: Industrial microbiology
The commercial use of microbes for economic and environmental benefits is called Industrial Microbiology.
Definition: Probiotics
Milk or food products that contain active beneficial microorganisms such as Lactobacillus, Lactobacillus casei, Acidophilus, and Bifidobacterium bifidum which improve intestinal health is called probiotics.
Define antibiotic.
- Carbon compounds obtained from some bacteria and fungi for destroying or preventing the growth of harmful micro-organisms are called ‘Antibiotics’.
- Examples of antibiotics: Penicillin, ampicillin,
Definition: Antibiotics
Carbon compounds obtained from certain bacteria and fungi that destroy or inhibit the growth of harmful microorganisms and are used in the treatment of infectious diseases is called antibiotics.
Definition: Bio-fuel
Renewable fuels obtained from biological sources and available in solid, liquid, and gaseous forms, which are used as an important source of energy is called bio-fuel.
Key Points
Key Points: Microbial Role in Dairy Products
| Aspect | Dairy Product | Microorganisms Used | Key Process | Important Compounds / Enzymes | Final Characteristics |
|---|---|---|---|---|---|
| Milk preservation | All dairy products | Naturally occurring bacteria | Pasteurization followed by fermentation | Lactic acid | Improved shelf life, texture, taste, and flavour |
| Yoghurt production | Yoghurt | Streptococcus thermophilus and Lactobacillus delbrueckii | Lactose fermentation and protein coagulation | Lactic acid, acetaldehyde | Thick consistency, characteristic flavour, probiotic nature |
| Butter production | Butter | Microbes (cultured butter only) | Cream fermentation | Diacetyl | Butter flavour and aroma |
| Cheese initiation | Cheese | Lactobacillus lactis, L. cremoris, Streptococcus thermophilus | Acid production and curd formation | Lactic acid | Sour taste and dense curd |
| Cheese coagulation | Cheese | Fungal source (modern method) | Whey removal and curd cutting | Protease enzyme (rennet substitute) | Firm texture |
| Cheese ripening | Cheese | Selected microbes | Pressing, salting, and storage | Flavouring pigments and enzymes | Soft, semi-hard, or hard cheese based on ripening period |
Key Points: Yeast and Microbes in Bread Making
Key Points: Vinegar Production
- Vinegar is chemically 4% acetic acid (CH₃COOH) and is used for flavouring and food preservation.
- Ethanol is produced by fermentation of sugars using yeast (Saccharomyces cerevisiae).
- Ethanol is converted into acetic acid by bacteria Acetobacter and Glucanobacter.
- Acetic acid is purified, pasteurized, and preserved by adding a small amount of SO₂ to obtain vinegar.
- Microbial fermentation is used in beverage production such as wine and cider using Saccharomyces cerevisiae, and in coffee and cocoa processing for seed separation.
Key Points: Microbial Enzymes
- Microbial enzymes are used instead of chemical catalysts as they work at low temperature, pH, and pressure, saving energy and reducing corrosion and pollution.
- These enzymes are highly specific, reusable, eco-friendly, and minimize formation of unwanted by-products, thereby reducing purification cost.
- Microbial enzymes are widely used in detergents, food processing (cheese, syrups), textile, leather, paper, and chemical industries.
- Microbial processing produces organic acids, gums (xanthan gum), vitamins, flavours, colours, emulsifiers, and sweeteners, which are extensively used in food and industrial products.
Key Points: Microbial Pollution Control
- Microbes play a vital role in pollution control by decomposing solid waste, sewage, and toxic pollutants through processes like composting, biogas production, and bioremediation.
- In landfilling, microbes decompose biodegradable urban waste to form compost, while plastic lining prevents soil pollution due to leaching.
- During sewage treatment, microbes decompose organic matter, destroy pathogens, release methane and CO₂, and make treated water environmentally safe.
- Microbes are used in clean technology to remove sulphur from fuels, detoxify metals, and decompose industrial chemicals and xenobiotics.
- Specialized microbes degrade pollutants such as petroleum oil (hydrocarbonoclastic bacteria), plastics (PET), rubber, acid rain compounds, and uranium salts, thereby protecting soil and water resources.
