Microorganisms in fermentation (e.g., yoghurt, brewing) - Biology IGCSE Study Notes

Fermentation is a metabolic process that allows microorganisms to convert carbohydrates, primarily sugars, into alcohol, organic acids, or gases under anaerobic conditions (absence of oxygen). Yeasts, such as Saccharomyces cerevisiae, and bacteria such as Lactobacillus species are predominately used in this process. In the production of yoghurt, Lactobacillus bulgaricus and Streptococcus thermophilus ferment lactose (milk sugar) into lactic acid, giving yoghurt its tangy taste and thick texture while also preserving the milk. During brewing, yeast fermentation transforms malt sugars into ethanol and carbon dioxide, which is critical for the production of beer. The efficiency and safety of these fermentation processes are paramount, as they ensure product quality and safety for consumers. This biological process has vast implications in the food and beverage industry, making it a pivotal aspect of biotechnology.

1. Fermentation: A metabolic process converting sugars to acids, gases, or alcohol in the absence of oxygen. 2. Yeast: Fungi used in fermentation; Saccharomyces cerevisiae is commonly employed in brewing. 3. Lactic Acid Bacteria (LAB): Bacteria, including Lactobacillus, that convert lactose into lactic acid in yoghurt production. 4. Anaerobic Respiration: The process through which organisms obtain energy without oxygen, typically involving fermentation. 5. Substrate: A substance on which an organism acts; for fermentation, this is often a sugar source. 6. Ethanol: An alcohol produced during fermentation, crucial in brewing and alcoholic beverage production. 7. Lactose: A sugar found in milk, fermented by bacteria in yoghurt production. 8. Carbon Dioxide: A gas produced during fermentation, contributing to the carbonation in beer. 9. Fermentation Temperature: Optimal temperatures vary by microorganism; for example, yoghurt cultures thrive at around 43°C. 10. Benefits of Fermentation: Includes preservation, enhancement of flavor, and increased nutritional value of products. 11. Commercial Fermentation: Large-scale production using specific strains of microorganisms to ensure consistent product quality. 12. Bioreactor: A vessel where fermentation is carried out under controlled conditions, crucial for ensuring optimal growth and productivity of microorganisms.