Construction of low acetaldehyde production brewing yeast with traditional mutagenesis strategy

Yeast and Fermentation Session
jinjing wang, jiangnan university, wuxi, jiangsu, china
Co-author(s): Qi Li, Jiangnan University, Wuxi, China

ABSTRACT: Higher acetaldehyde concentration in beer is one of the main concerns of the current beer industry in China. Acetaldehyde is always synthesized during beer brewing by the metabolism of yeast. Here, using ethanol as the sole carbon source and 4-methylpyrazole as the selection marker, we constructed a new mutant strain with lower acetaldehyde production and improved ethanol tolerance via traditional mutagenesis strategy. European Brewery Convention tube fermentation tests comparing the fermentation broths of the mutant strain and the industrial brewing strain showed that the acetaldehyde concentration of the mutant strain was 81.67% lower, whereas its resistant staling value (RSV) was 1.0-fold higher. Alcohol dehydrogenase catalyzes the reaction of acetaldehyde formation from ethanol. Owing to the mutation of the alcohol dehydrogenase, the alcohol dehydrogenase activity of the mutant strain decreased to about 30% of the wild-type strain. In the meantime, the ethanol tolerance of the mutant strain increased by about 0.5–1% more than wild-type strain, which is very important to yeast strain, especially under high gravity or very high gravity fermentation conditions. The mutant strain constructed in this work could be applied to the beer industry directly due to its better performance in the brewing process.

Jinjing Wang received a Ph.D. degree in genetics from the Institute of Microbiology, Beijing, China. She spent a year and a half at Washington State University as a visiting scholar. She began employment with Jiangnan University in 2011 as an assistant professor in the Brewing and Enzyme Technology Center of the Biological Engineering School.