Identification of multiple-derived peptides produced by Saccharomyces cerevisiae involved in malolactic fermentation inhibition.

An oenological strain of Saccharomyces cerevisiae was previously shown to produce a 5-10 kDa peptidic fraction responsible for the inhibition of malolactic fermentation (MLF). In the present study, we aim to further purify the anti-MLF peptides of this fraction. The yeast fermented synthetic grape juice medium was fractionated by ammonium sulfate precipitation combined with ultrafiltration. The 5-10 kDa fraction recovered at a saturation degree of 60%-80% was the only fraction that inhibited both the bacterial growth and the malate consumption in vivo. It also inhibited the malolactic enzyme activity in vitro at a pH range between 3.5 and 6.7. Therefore, it was purified by both anion and cation exchange chromatography. The eluates that inhibited the malolactic enzyme activity in vitro were migrated on Tricine SDS-PAGE and the protein bands were excised and sequenced by LC-MS/MS. The sequencing revealed nine peptides originating from eight proteins of S. cerevisiae. Two GAPDH cationic fragments of 0.9 and 1.373 kDa having a pI of 10.5 and 11 respectively, Wtm2p and Utr2p anionic fragments of 2.42 kDa with a pI of 3.5 and 4 respectively were thought to contribute the most to the MLF inhibition.