Identification of Dominant Strains in Liu Shenqu by MALDI-TOF MS and DNA Sequencing Methods

Abstract

Liu Shenqu has been widely used to treat the weakness of spleen and stomach, indigestion, etc. in China. As a fermented product, strains make an important role in the fermentation process, which will affect the quality of Liu Shenqu. Therefore, it is important to identify the dominant strains in the fermentation process of Liu Shenqu. In this study, we aim to identify the dominant strains in Liu Shenqu through Matrix-assisted laser desorption ionization time-of-flight mass spectrometry Biotyper (MALDI-TOF MS) combined with DNA sequencing methods. This research involves two parts: MALDI-TOF MS identified the dominant bacteria, and the Sanger sequencing method identified the dominant fungi. Total number of 21 bacterial species were identified by MALDI-TOF MS and 21 fungi species were identified by Sanger sequencing. We searched the types of enzymes in the identified strains above based on the GB2760-2014 National Food Safety Standard and Food Additives Use Standard. Compared the types of enzymes reported in Liu Shenqu with the types of enzymes retrieved in GB2760-2014 National Food Safety Standard and Food Additives Use Standard, Aspergillus oryzae and Rhizopus oryzae were finally determined to be the dominant strains in Liu Shenqu. This study showed that MALDI-TOF MS combined with DNA sequencing methods could be used for identification the dominant strains in Liu Shenqu. This strategy is promising for application to strains identification of other fermented products.