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

Abstract

Abstract Background Liu Shenqu has been widely used to treat the illnesses of spleen and stomach, indigestion, etc. in China. As a fermented product, strains play 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. Objectives Identify dominant strains in the fermentation process of Liu Shenqu and provide a theoretical reference for the fermentation of fixed strains in industrial production. Methods In this study, we aim to identify the dominant strains in Liu Shenqu through matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) combined with DNA sequencing methods. This research involves two parts: MALDI-TOF MS identifies the dominant bacteria, and the Sanger sequencing method identifies the dominant fungi. Results A total 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 based on the GB2760-2014 National Food Safety Standard and Food Additives Use Standard (China). We 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 determined to be the dominant strains in Liu Shenqu. Conclusion This study showed that MALDI-TOF MS combined with DNA sequencing methods could be used for identification of the dominant strains in Liu Shenqu. This strategy is promising for application to strain identification in other fermented products. Highlights Fresh products were frozen and transported in bacteria-preserving tubes to ensure the authenticity of the number and type of strains of Liu Shenqu. MALDI-TOF MS combined with DNA sequencing methods was successfully applied to identify the dominant strains in the fermentation process of Liu Shenqu for the first time. Aspergillus oryzae and Rhizopus oryzae were determined to be the dominant strains in Liu Shenqu.