Application of the acetolactate decarboxylase from Lactobacillus casei for accelerated maturation of beer

Abstract

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.

Purification of α-acetolactate decarboxylase from Lactobacillus casei DSM 2547

“…This was not confirmed in our laboratory as only addition of zinc could stabilize partially purified ct-aceto-lactate decarboxylase from L.casei DSM 2547 in solutions at pH 4.2 containing yeast cells (9), addition of thiamine pyrophosphate had no effect.…”

“…The purification scheme in Table I shows that the final product boxylase. The assay was performed in acetate buffer ( 9 ) or phosphate buffer (---==--) at the indicated pH values for 30 rain at 37 ~ after which the acetoin formed was estimated colorimetrically.…”

“…However, the practical use of this procedure is complicated by a limited stability of the Aerobacter ct-acetolactate decarboxylase at the pH of beer (7). A search for an enzyme with higher stability in the acid pH region led, among others (7,8,10), to an a-acetolactate decarboxylase in a strain of Lactobacillus casei which met this criteria (8,9). This enzyme removed as expected all ct-acetolactate from freshly fermented beer within 48 hrs.…”

“…Enzymes with the ability to decarboxylate ct-acetolactate are widely found amoung bacterial strains but not in other groups of microorganisms (7,8,10). The only ct-acetolactate decarbo~ylase (EC 4.1.1.5.)…”

“…This enzyme has more recently been demonstrated to be effective for removal of a-acetolactate from freshly fermented beer and thus for acceleration of the beer maturation process (6). However, the practical use of this procedure is complicated by a limited stability of the Aerobacter ct-acetolactate decarboxylase at the pH of beer (7). A search for an enzyme with higher stability in the acid pH region led, among others (7,8,10), to an a-acetolactate decarboxylase in a strain of Lactobacillus casei which met this criteria (8,9).…”