Disruption of brewer's yeast Alcohol Dehydrogenase II gene and reduction of acetaldehyde content during brewery fermentation

In an attempt to reduce acetaldehyde content in the final beer product, mutant strains of brewer's yeasts were constructed by genetic homologous recombination, in which the alcohol dehydrogenase II (ADHII) gene was partially disrupted. The strains were tested on the scale of 100 L of pilot fermentation. Compared with that of the parent yeast, the results showed an obvious decline of acetaldehyde content with mutant yeast at the end of fermentation, especially when fermentable sugar was depleted. The final acetaldehyde content of beer obtained with parent and mutant yeasts was 7.82 and 2.54 mg/L, respectively. However, no evident differences in brewing performance, such as the ability to utilize sugar, growing, and flocculating, were revealed between parent and mutant yeasts. Additionally, no clear differences were found between parent and mutant yeasts in the production of other volatile compounds and sensory analysis of attributes. Therefore, these approaches uncover the possibility of reducing and controlling acetaldehyde content during beer production.