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Molecular basis and regulation of flocculation in Saccharomyces cerevisiae and Saccharomyces pastorianus - a review - YEAST SPECIAL
K. Seibel, R. Schmalhaus, M. Haensel and F. Weiland

Flocculation is an important facet of yeast behaviour and widely exploited in the brewing industry as an effective, low cost and natural mechanism for yeast removal from beer. Phenotypic characterisation has been conducted for decades and has revealed several different flocculation types based on their inhibition by different types of sugars. However, recent research has unveiled that not all adhesin proteins involved in flocculation fit into these two categories. Over the last 10 years, the crystal structures of the sugar-binding domains of flocculins Flo1p and Lg-Flo1p have been elucidated and gave important insights into the underlying molecular basis of the different flocculation types. Together with the vast research into the cellular regulation and the intrinsic genetic instability of these two major flocculation proteins, it has become clear that a purely descriptive characterisation of flocculation is insufficient and needs to be amended with molecular biological and genetic research techniques. This is especially true in light of aiming to control flocculation during beer fermentation. Therefore, this review aims to summarise the current understanding of the underlying molecular biology and cellular signalling mechanisms involved in flocculation to give brewing scientists an adequate overview of the current state of research.

Descriptors: flocculation, Saccharomyces cerevisiae, Saccharomyces pastorianus, gene regulation, cell signalling, FLO gene family

BrewingScience, 74 (March/April 2021), pp. 39-50