Fermentation assays reveal differences in sugar and (off-) flavor metabolism across differentBrettanomyces bruxellensisstrains

Abstract

Brettanomyces (Dekkera) bruxellensis is an ascomycetous yeast of major importance in the food, beverage and biofuel industry. It has been isolated from various man-made ecological niches that are typically characterized by harsh environmental conditions such as wine, beer, soft drink, etc. Recent comparative genomics studies revealed an immense intraspecific diversity, but it is still unclear whether this genetic diversity also leads to systematic differences in fermentation performance and (off-)flavor production, and to what extent strains have evolved to match their ecological niche. Here, we present an evaluation of the fermentation properties of eight genetically diverse B. bruxellensis strains originating from beer, wine and soft drinks. We show that sugar consumption and aroma production during fermentation are determined by both the yeast strain and composition of the medium. Furthermore, our results indicate a strong niche adaptation of B. bruxellensis, most clearly for wine strains. For example, only strains originally isolated from wine were able to thrive well and produce the typical Brettanomyces-related phenolic off-flavors 4-ethylguaiacol and 4-ethylphenol when inoculated in red wine. Sulfite tolerance was found as a key factor explaining the observed differences in fermentation performance and off-flavor production. Sequence analysis of genes related to phenolic off-flavor production, however, revealed only marginal differences between the isolates tested, especially at the amino acid level. Altogether, our study provides novel insights in the Brettanomyces metabolism of flavor production, and is highly relevant for both the wine and beer industry.

Microbial acidification, alcoholization, and aroma production during spontaneous lambic beer production

“…Further, some strains are unable to use nitrate or nitrite, due to the lack of one or more essential genes involved in nitrate assimilation . Moreover, both the fermentation performance and aroma production are dependent on both the yeast strain and medium composition, including available carbohydrates, nitrogen sources, volatile precursors, stressors, etc …”

“…[129][130][131] Moreover, both the fermentation performance and aroma production are dependent on both the yeast strain and medium composition, including available carbohydrates, nitrogen sources, volatile precursors, stressors, etc. 132…”

High complexity and degree of genetic variation inBrettanomyces bruxellensispopulation

“…It has also been found associated with other food or industrial processes, such as kombucha or bioethanol, for which its contribution is still unclear (Beckner, et al 2011;Teoh, et al 2004). The opposite contributions of B. bruxellensis in fermentation processes raised a growing interest in this species, and high phenotypic variability regarding for example sugar metabolism or nitrogen source utilization has been highlighted among the isolates in various studies (Borneman, et al 2014;Crauwels, et al 2015;Crauwels, et al 2017).…”

The Impact of Simple Phenolic Compounds on Beer Aroma and Flavor

“…Commercial interest in these yeasts has resulted in a growing body of data related to their contribution to wine and beer flavor. Genetic and physiological analysis of B. bruxellensis strains that vary in geographical and source environment suggests niche adaptation, as strains cluster more strongly by the isolation environment than by geography [64][65][66][67][68]. There are notable differences between beer and wine strains at the whole genome level and for SNPs, including genes involved in volatile phenol production [66,67].…”

“…The Brettanomyces PAD enzyme has been characterized and cloned from several strains, including beer and wine isolates. The production of vinyl phenols is strongly strain and growth medium dependent [67,69,70].…”