An improved method for MALDI-TOF analysis of wine-associated yeasts

Although MALDI-TOF mass spectrometric analysis has been applied to the characterization of yeast species important in winemaking, relatively few taxa have so far been examined, and the value of low mass peaks for identification has not, to our knowledge, been previously determined. We describe a modified (pre-mixing) procedure for extraction of low (m/z 500–4000) - and high (m/z 2000–20,000) mass range moieties detected by MALDI-TOF and compare it with a previously described, proposed standard method based on a dried-droplet approach. Thirty-three strains representing 21 yeast species were examined. We found our modified method consistently yielded more discriminatory peaks and a broader mass range detection than the proposed standard method for the species examined. Cluster analyses of MALDI-TOF profiles also indicated better separation between species when the pre-mixing method was used, especially where high mass features were used. The use of low mass features may be useful for strain-level discrimination.