No abstract

~ Present address: Novo Industri A/S, Novo All& DK-2880 BagsvaerdKeywords: et-acetolactate, a-acetolactate decarboxylase, acetoin, diacetyl, lactic acid bacteria, beer maturation, HPLC ct-Acetolactate decarboxylase has been purified to homogeneity, by fast protein liquid chromatography and high performance elution chromatography, from a partially purified ct-acetolactate decarboxylase preparation from Lactobacillus casei DSM 2547. The pure enzyme exhibited a specific activity of 375 kU. mg-' and exerted its optimal activity at pH 4.5 to 5.0 and at a temperature of 40 ~ Its isoelectric point was estimated to pH 4.7 and its molecular weight was found to be 48,000. The enzyme was inhibited by o-phenanthroline and could be partially reactivated by zinc ions. An HPLC method for the determination of ct-acetolactate is described.

The acetolactate decarboxylase produced by Lactobacillus casei DSM 2547 has been tested as an aid for accelerated removal of the diacetyl precursor acetolactic acid from beer. Addition of the enzyme to freshly fermented beer has been shown to effect efficient removal of the diacetyl precursor while addition of the decarboxylase to wort prior to pitching was found to lead to subsequent inactivation of the enzyme during the fermentation. It has been shown that zinc is a component of the acetolactate decarboxylase system, and that growing yeast cells remove the zinc ions.