MALOLACTIC FERMENTATION IN GRAPE MUSTS BY A GENETICALLY-ENGINEERED STRAIN OF SACCHAROMYCES-CEREVISIAE

Malate enters Saccharomyces cerevisiae by simple diffusion. Due to the lack of a malate transporter and the low affinity of the S. cerevisia e malic enzyme, this yeast is unable to degrade malate efficiently. We have constructed a malolactic yeast strain by co-expressing the malat e permease gene (mae 1) of the fission yeast Schizosaccharomyces pombe and the Lactococcus lactis malolactic gene (mleS) in S. cerevisiae. T he recombinant strain of S. cerevisiae transported malate and actively metabolized malate to lactate within three days in Cabernet Sauvignon and Shiraz grape musts at 20 degrees C. The malolactic fermentation i n Chardonnay grape must was completed within seven days at 15 degrees C. The efficient degradation of malate in grape musts is important to wineries and the availability of malolactic yeasts will allow the earl y application of cellar operations for storage and aging of wine.