Lactic acid bacteria diversity of fresh rice noodles during the fermentation process, revealed by culture-dependent and culture-independent methods

Rice noodles, a traditional Chinese food, are made using natural fermentation. The fermentation process plays an important role for the texture and flavour, which are due to the metabolism of the microorganisms involved, especially lactic acid bacteria (LAB). However, the fermentation of rice noodles is a non-controlled and spontaneous process; the quality of products is not stable. In order to improve and stabilize the quality of the production, the LAB functions on rice noodles during fermentation need to be elucidated. In this study, the community composition and dynamics of LAB associated with the fermented rice were investigated by using a culture-dependent approach in combination with a culture-independent approach, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Sixty-four strains were isolated by culture-dependent analysis in different rice noodles factories and mainly 10 species in total were found. In addition, PCR-DGGE detected 17 species (including uncultured species) in total. Seven Lactobacillus species were detected by both methods, namely Lb. delbrueckii, Lb. salivarius, Lb. helveticus, Lb. reuteri, Lb. fermentum, Lb. amylovorus and Lb. oris, and the rest were detected by different methods separately. The potential role of these predominant LAB in the fermentation process is discussed. In general, the two techniques complement each other to give a better understanding on the LAB composition, which is necessary for the isolation of functional strains and improvement of the quality and consistency of rice noodles.