Fermentation and Microbes

Definition

Fermentation is the breakdown of sugars by microorganisms in the absence of oxygen, used by humans to make food, drink, and industrial products.

Key points

• Yeast (a fungus) ferments sugar into ethanol and carbon dioxide; the carbon dioxide makes bread rise, and the ethanol is the basis of alcoholic drinks.
• Bacteria such as Lactobacillus ferment milk sugar (lactose) into lactic acid, turning milk into curd (yogurt) and giving it a sour taste.
• Fermentation is a form of anaerobic respiration (without oxygen); in human muscles, lactic-acid fermentation during heavy exercise causes muscle fatigue and cramps.
• Microbes are used industrially to make antibiotics (penicillin from Penicillium mould), vinegar, cheese, idli and dosa batter, and many enzymes.
• Biogas (mainly methane) is produced by anaerobic bacteria breaking down organic waste, a renewable fuel from a microbial process.

Why it matters for CAPF

Yeast making bread rise and alcohol, Lactobacillus making curd, fermentation as anaerobic respiration, and microbial production of antibiotics and biogas are standard biology and everyday-science facts.

Common confusion

Fermentation happens without oxygen (anaerobic), so it is not the same as ordinary aerobic respiration; yeast produces alcohol and carbon dioxide, while Lactobacillus produces lactic acid, two different products. Muscle cramps after exercise come from lactic-acid build-up, the same chemistry as souring milk.

Related concepts

concept enzymes, concept antibiotics vs antivirals, concept biofuels

Parent note

biology cell and classification