The role of yeast in fermentation

The role of yeast in fermentation
Fermentation is a process of breaking down sugar molecules to alcohol and carbon dioxide in the absence of oxygen. From fermentation, many products are obtained, such as alcoholic beverages, breads, perfumes, medicines, etc. This finding has been discovered a long time ago by our ancient people. However, many scientists studied the principle and mechanism involved in the production of various products as a result of fermentation. Their studies stated that, fermentation occurs in the presence of micro-organisms. Gay-Lussac in 1815 conducted an experiment with unfermented grape juice, which started fermenting on adding yeast and this confirmed the microbes play a major role in fermentation. Many types of micro-organisms are used in fermentation but people prefer using yeast because of their ability to tolerate and perform well in concentrated solution. In addition, they are single-celled and eukaryotic fungi.

In the media, when yeast cells multiply, the glucose concentration decreases and ethanol concentration increases. This is how fermentation occurs. Usually, higher concentration of ethanol is toxic to the cells but yeast cells tolerate the maximum of 10-15% of it while the other micro-organisms could not. In addition, yeast cells tolerate fermentation inhibitor, and continue sugar metabolism too efficiently. They utilise sugar molecules more efficiently in the absence of oxygen and produce 95% of alcohol. It was stated in Cleantech magazine that, yeast cells are capable of digesting hexoses efficiently but poor in digesting pentoses. This indicates that they are capable of growing in minimal nutrient and producing a high yield of ethanol. As Pasteur stated, fermentation and yeast multiplication occur in parallel; whereas, this is not the case with other microbes.

Yeast poses some negative effects in fermentation called as negative Pasteur effects, which reduce fermentation (as a result of the shortage of adenosine diphosphate (ADP) and nicotinamide adenine dinucleotide (NAD) in the oxidation of phosphoglyceraldehyde to acetaldehyde) and increase the growth rate of yeast. In general, yeast plays a major role in fermentation by increasing the yield of alcohol and carbon dioxide, and is utilised by many industries worldwide to produce various fermented beverages and other fermented products.


How to cite this article:
Eva Edward Jayarajan. The role of yeast in fermentation. BioLim O-Media. 20 January, 2016. 4(1).
Available from: http://www.biolim.com/read/BOMA0103.