Fermentation In fermentation ATP is synthesized by substrate

Fermentation In fermentation, ATP is synthesized by substrate level phosphorylation at the. The growth of fermenting bacteria is limited by the fact that the organic acids they produce in the cell as a result of their low energy and metabolism are toxic to the cell. Pyruvate formed by oxidation of glucose by fermentative bacteria is converted to various compounds such as ethanol, lactate, butyrate. Fermentations are referred to, for example, alcohol fermentation, lactic acid fermentation. Pyruvate is fermented by microorganisms in five main ways.

Pasteur Effect: Some microorganisms (such as yeasts) can perform both fermentation and respiration. If conditions are anoxic fermentation occurs, and when O 2 is present (as last electron acceptor) the cell obtains and prefers more energy by respiration.

Hydrolysis of lignocellulosic biomass produces sugars such as glucose, xylose, arabinose, galactose and mannose. Unfortunately, S. cerevisae, used in the production of industrial ethanol, can only metabolize glucose to ethanol under anaerobic conditions. Therefore, different strategies have been developed to obtain microorganisms capable of metabolizing other sugars in addition to glucose.

These strategies include: Selection of a good ethanol producer but a host who can use narrow range sugars or a weak ethanol producer but a host that can use wide range sugars Transmitting plasmids containing genes to promote the use of a wide range of sugars or improve ethanol production to this host

Improvement of experiments Integration of genes to chromosome to increase genetic stability In order to improve ethanol production, it can be summarized as inactivation of biosynthetic pathways that lead to the formation of unwanted by-products.

Another strategy is the development of organisms capable of directly metabolizing cellulose and hemicellulose. In this way, the hydrolysis step with the enzyme is eliminated. This method is the latest technology developed for the production of ethanol from lignocellulosic raw materials. Therefore, it is not as advanced as other strategies.

A good ethanol producer microorganism should have: Able to convert sugars from multi-biomass into ethanol Be able to tolerate inhibitory compounds formed during pretreatment No need for expensive nutrients It should have high growth rate and ethanol production capacity even under undesirable conditions such as low p. H and high temperatures.

Mesophilic microorganisms are generally used in ethanol production. However, some strains capable of using thermophilic sugar can also be used for this purpose, and this has some advantages: High fermentation temperature eliminates contamination problem. High volatility of ethanol at fermentation temperature reduces the recovery cost of ethanol. Continuous removal of the product under vacuum reduces ethanol inhibition.