Study of Yeast Identification Using MALDI-TOF MS

After culturing 75 strains of 19 yeast species from food on potato dextrose agar medium at 25 degrees C for 5 days, mass spectra were acquired using VITEK MS (TM) plus to prepare SuperSpectra (SSp). Verification of the prepared SSp showed that the reliability of identification was more than 80 % except for Schizosaccharomyces spp., Sterigmatomyces elviae, Starmerella apicola, S. etchellsii, Wickerhamomyces subpelliculosus, Zygosaccharomyces rouxii, and Z. bisporus. It was difficult to distinguish Z. bailii, Z. parabailii, Z. pseudobailii, Z. mellis, and Z. siamensis, by using their SSp, but they can be identified as Z. bailii complex for Z. bailii, Z. parabailii and Z. pseudobailii, and Z. mellis-siamensis complex for Z. mellis and Z. siamensis. The identification reliability level was affected by the medium used for cultivation of yeast. For the Brettanomyces (Dekkera) spp., there were cases where they were difficult to identify when a mass spectrum with peaks that had a sufficient number and intensity was not obtained, or when the major peaks were similar. Improvement of the methods for sample treatment and SSp creation were required.