Fundamental investigation and applied studies on non-Saccharomyces yeasts in non-alcoholic and low alcohol beer brewing

Abstract

Non-alcoholic and low alcohol beer (NABLAB) is enjoying growing popularity owing to consumer lifestyle changes, improved production methods and stricter legislation. Among the biological methods for their production, particularly research into non-Saccharomyces yeasts has gained momentum in recent years in order to produce NABLAB with novel flavor characteristics in an easy-to-apply manner. In a proof-of-concept study, five selected non-Saccharomyces species isolated from kombucha showed to perform just as well in laboratory-scale trials in wort as commercially applied species Saccharomycodes ludwigii. In a subsequent study, species of the Cyberlindnera genus were found to produce a pleasant, fruity flavor in wort. Fermentation parameters were optimized by means of response surface methodology (RSM) and the resulting non-alcoholic beer (NAB; 0.36% ABV) produced with Cyberlindnera subsufficiens on pilot-scale (60 L) had a significantly more fruity and significantly less wort-like aroma compared to two commercial NABs. Regarding low alcohol beer (LAB), the yeast species Lachancea fermentati was introduced to create LAB by harnessing the species’ uncommon ability to produce significant amounts of lactic acid (LA) during alcoholic fermentation. Compared to a Saccharomyces cerevisiae brewers’ yeast, L. fermentati produced less ethanol (–15%) while producing 1.3 g/L lactic acid, giving the beer a sour taste. In a follow-up study, four L. fermentati isolated from individual kombucha cultures were investigated in detail. The strains genotypes and phenotypes where shown to be diverse, correlating with the strains’ geographical origin. LA production was optimized via RSM, where low pitching rate, high fermentation temperature, and a high initial glucose concentration resulted in the highest LA concentrations (max. 1.6 g/L). LAB (1.26 %ABV) produced with L. fermentati by stopped fermentation showed to have a balanced ratio of acidity from lactic acid to residual wort sweetness. In conclusion, the results of this thesis give prospect to future studies with non-Saccharomyces yeasts and strengthen their position as a serious and applicable alternative to established methods in NABLAB brewing.