Isolation, characterization and identification of lactic acid bacteria and yeasts from sour Mifen, a traditional fermented rice noodle from China

Aims:  Considering the effect of natural fermentation on the textural improvement of fermented rice noodles in China and South Asia, and given the lack of reports concerning microbial populations and structure in the fermentation process, this study aims to determine the number of viable micro-organisms and identify the species isolated from the local factories, and to assess their potential use as a starter culture from their enzymatic profiles.
Methods and Results:  Fourteen samples from three local factories were analysed for the presence of micro-organisms. A total of 170 lactic acid bacteria (LAB) and 96 yeasts were isolated from the factories. The isolates were phenotypically characterized by using API 50 CHL kits, API 20 Strep kits, API ID 32 C kits and by performing additional biochemical tests. The enzymatic profiles of isolates were assessed by using API ZYM kits. Lactobacillus plantarum and Saccharomyces cerevisiae were identified as predominant species in the fermented supernatants. A majority of the isolates of LAB and yeasts displayed activities of α-glucosidase, β-glucosidase, lipase and trypsin.
Conclusions:  The microbial composition and strain characteristics present in the fermentation supernatant demonstrate that a majority of micro-organisms have the ability to digest starch, sugar, protein or lipid. It supports our previous work in which the rice starch was modified and purified by fermentation and thus improves the texture of rice noodles.
Significance and Impact of the Study:  The dominant strains would be important in developing a starter culture. The results can form the basis for the improvement of product quality and consistency.