Rapid identification of hiochi bacteria by matrix-assisted laser desorption/ionization mass spectrometry

The rapid identification of the sake spoilage microorganisms (hiochi bacteria) by matrix-assisted laser desorption/ ionization mass spectrometry (MALDI-MS) using ribosomal proteins as biomarkers was developed. Ribosomal proteins isolated and purified from five representative hiochi bacteria (Lactobacillus fructivorans, L. hilgardii, L. paracasei subsp. paracasei, L. paracasei subsp. lolerans, and L. rhamnosus) as references were characterized by MALDI-MS. Among the peaks observed both from purified ribosomal protein samples and cell lysates in the range of m/z 6000 similar to 12000, the 15 strongest peaks were selected for each reference hiochi bacteria to make a biomarker peak database. Since the m/z values of several biomarker peaks were identical to each bacteria, rapid discrimination and identification of hiochi bacteria could be performed at the species as well as the subspecies level. This method was then applied for the rapid identification of hiochi bacteria generated in a sake brewery. The m/z values of MALDI mass spectra of the hiochi bacteria sample suggested that this bacteria could be identified as L. paracasei subsp. paracasei or closely-related species.