Quantification of strains in mixed lager yeast cultures using microsatellite PCR and GeXP

Abstract

Mixed culture fermentation with lager yeast is relatively new in brewing. Maintaining the proportion of strains during fermentation is important to assure the quality of beer and accordingly needs to be monitored. The current discriminatory methods have limited application for lager strains. In the present study, a rapid method to monitor the strain proportion of strains in mixed samples of two different lager yeast strains was developed using microsatellite polymerase chain reaction (PCR) and GeXP Genetic Analysis System. Microsatellite markers in the lager yeast genome were searched using SSR Hunter software. Quantitative PCR using these microsatellite markers was performed and PCR products were analysed by capillary electrophoresis. One locus - mitochondrial carnitine acetyltransferase – was found to discriminate the two strains. A standard curve was generated based on the premixed samples of the two strains enabling the proportion of the stains to be determined. This method is a fast and reliable approach to monitor the strain proportion of mixed lager yeast fermentation. © 2020 The Institute of Brewing & Distilling