Affiliation:
1. 0000 0004 0400 1852 grid.6324.3 VTT Technical Research Centre of Finland Ltd P.O. Box 1000 Tietotie 2, VTT FI-02044 Espoo Finland
2. 0000000108389418 grid.5373.2 Department of Biotechnology and Chemical Technology Aalto University, School of Chemical Technology P.O. Box 16100 Kemistintie 1, Aalto 00076 Espoo Finland
Abstract
Abstract
Diacetyl contributes to the flavor profile of many fermented products. Its typical buttery flavor is considered as an off flavor in lager-style beers, and its removal has a major impact on time and energy expenditure in breweries. Here, we investigated the possibility of lowering beer diacetyl levels through evolutionary engineering of lager yeast for altered synthesis of α-acetolactate, the precursor of diacetyl. Cells were exposed repeatedly to a sub-lethal level of chlorsulfuron, which inhibits the acetohydroxy acid synthase responsible for α-acetolactate production. Initial screening of 7 adapted isolates showed a lower level of diacetyl during wort fermentation and no apparent negative influence on fermentation rate or alcohol yield. Pilot-scale fermentation was carried out with one isolate and results confirmed the positive effect of chlorsulfuron adaptation. Diacetyl levels were over 60% lower at the end of primary fermentation relative to the non-adapted lager yeast and no significant change in fermentation performance or volatile flavor profile was observed due to the adaptation. Whole-genome sequencing revealed a non-synonymous SNP in the ILV2 gene of the adapted isolate. This mutation is known to confer general tolerance to sulfonylurea compounds, and is the most likely cause of the improved tolerance. Adaptive laboratory evolution appears to be a natural, simple and cost-effective strategy for diacetyl control in brewing.
Publisher
Oxford University Press (OUP)
Subject
Applied Microbiology and Biotechnology,Biotechnology,Bioengineering
Cited by
27 articles.
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