CONSTRUCTION OF A WINE YEAST STRAIN CAPABLE OF MALOLACTIC FERMENTATION

WINE IS THE PRODUCT OF BOTH YEAST AND BACTERIAL FERMENTATIONS OF GRAPE JUICE. THE ALCOHOL CONTENT OF WINE IS A RESULT OF THE ANAEROBIC CONVERSION OF SUGARS TO ETHANOLBY STRAINS OF THE YEAST SACCHAROMYCES CEREVISIAE. THE CONVERSION OF MALIC ACID TO LACTIC ACID IS ACCOMPLISHED BY ONE OR MORE SPECIES OF LACTIC ACID BACTERIA. THIS SO-CALLEDMALOLACTIC FERMENTATION IS IMPORTANT FOR THE REDUCTION OF MALIC ACID IN THE WINE PRIOR TO BOTTLING (TO REDUCE THE POSSIBILITY OF BACTERIAL GROWTH AFTER BOTTLING) AND FOR IMPROVING THE PALATABILITY OF THE WINE. SINCE BACTERIAL FERMENTATIONS DURING OR AFTER THE YEAST FERMENTATION ARE NOTALWAYS CONSISTENT (AND ARE SOMETIMES DETRIMENTAL), IT IS ATTRACTIVE TO CONSIDER ENDOWING YEAST WITH THE ABILITY TO CONVERT MALIC ACID TO LACTIC ACID, THUS ELIMINATING THE NECESSITY FOR A BACTERIAL FERMENTATION. THIS PROPOSAL SEEKSTO EXTEND THE WORK OF OTHERS IN CHARACTERIZING THE MALOLACTIC ENZYME GENE FROM LACTOBACILLUS DELBRUECKII AND TO EXPRESS THE GENE AT AN APPROPRIATE LEVEL IN A COMMERCIAL STRAIN OF SACCHAROMYCES CEREVISIAE.