BIOS 450 Microbial Fermentation

This set of flashcards covers key concepts related to microbial fermentation, its processes, and the types of products generated.

What are fermentations in microbial metabolism?

Fermentations are anaerobic metabolisms that do not require external electron acceptors, where microbes achieve redox balance and conserve energy by forming various fermentation products.

How do fermentations conserve energy?

Fermentations conserve energy through substrate-level phosphorylation reactions rather than through the formation of an ion gradient.

What types of fermentation products are commonly produced?

Common fermentation products include alcohols (like ethanol and isopropyl alcohol), organic acids (like acetic and lactic acid), and gases (like CO2 and H2).

What differentiates fermentation from anaerobic respiration?

Fermentation occurs in the absence of usable terminal electron acceptors and uses substrate as both electron donor and acceptor, while anaerobic respiration uses external electron acceptors.

What is the role of pyruvate in fermentation?

In fermentation, pyruvate is reduced to various fermentation products, which are then excreted.

What are the two major groups of enteric bacteria based on fermentation products?

Mixed-acid fermenters, which produce acetic, lactic, and succinic acids, and 2,3-butanediol fermenters, which produce butanediol, ethanol, and smaller amounts of acids.

What are the main pathways used to convert sugar phosphates to pyruvate during fermentation?

The main pathways are the Embden-Meyerhof (E-M) pathway, Entner-Doudoroff (E-D) pathway, phosphoketolase pathway, and combination pathways.

Describe the Stickland reaction.

The Stickland reaction involves the fermentation of amino acid pairs, where one amino acid is used as an electron donor and the other as an electron acceptor.

What types of microorganisms primarily perform lactic acid fermentation?

Lactic acid fermentation is primarily performed by lactic acid bacteria such as Lactobacillus and Streptococcus.

What are the key products of lactic acid fermentation?

The key products of lactic acid fermentation include lactic acid and ATP.

What distinguishes homofermentative from heterofermentative lactic acid bacteria?

Homofermentative bacteria produce only lactic acid and yield two ATP per glucose, while heterofermentative bacteria produce lactate, ethanol, CO2, and yield one ATP per glucose.