DEACIDIFICATION OF GRAPE JUICE WITH DEREPRESSED MUTANTS OF THE YEAST HANSENULA-ANOMALA

Transport and utilization of malic acid by the yeast Hansenula anomala are subject to glucose repression. Derepressed diploid mutant strains were obtained by hybridization of depressed haploid mutant strains of opposite mating type. Six diploid mutant strains displayed derepressed behaviour with respect to malic acid utilization in the presence of glucose up to 30% (w/v). Three of these diploid mutant strains, as compared with the parent strain, were able to degrade completely malic acid in grape juice without fermenting the sugars. In addition, using one diploid mutant strain together with a strain of the wine yeast Saccharomyces cerevisiae, it was possible to carry out a mixed microvinification in which deacidification occurred simultaneously with alcoholic fermentation.