BREWING PERFORMANCE OF A BREWERS-YEAST HAVING ALPHA-ACETOLACTATE DECARBOXYLASE FROM ACETOBACTER-ACETI SUBSP XYLINUM

The alpha-acetolactate decarboxylase (ALDC) gene from Acetobacter aceti subsp. xylinum was integrated stably into the chromosome of a brewer's yeast. Location of the integrated ALDC gene was analyzed by Southern hybridization and CHEF (contour clamped homogeneous electric field). It was confirmed that the ALDC gene was integrated in the rRNA locus of the chromosome XII. Laboratory-scale brewing tests were carried out to study brewing properties of the transformants in detail. Total diacetyl (DA) concentration in young beer of transformants was considerably lower than that of the control yeast. No practical difference in brewing properties (attenuation degree, flocculation, amino acids composition and volatile compounds) was observed between the transformant and the control yeast. Low productivity of total DA in transformants was stably maintained during the successive brewing test in laboratory scale.