ESTERASE ACTIVITY IN THE GENUS BRETTANOMYCES

Abstract

During the spontaneous fermentation of Iambic and the production of the typical Belgian beer Gueuze, yeasts of the genus Brettanomyces are always found. They are especially active in the 6 to 12 months fermentation period and during refermentation in the bottle. It was found that Brettanomyces yeasts show esterase activity towards a large number of esters but especially towards esters normally found in Gueuze: ethyl acetate, ethyl lactate, iso‐amyl acetate and phenethyl acetate. The esterase activity is expressed by whole cells of all Brettanomyces strains in our collection, but not by Saccharomyces or Kloeckera. The enzyme is partially purified by ammonium sulphate precipitation. It shows optimal activity at pH 7·6 for the hydrolysis of ethyl acetete and relative good stability at around 2°C. Levels of whole cell esterase activity are dependent on growth medium, aeration rate and temperature. Most interesting is the ester‐synthesising activity of this esterase. Its role and influence on the ester fraction of Iambic and Gueuze seem very likely, which may then be considered as the first confirmed function of Brettanomyces during this special fermentation process. 1982 The Institute of Brewing & Distilling