Deciphering microbial and metabolite dynamics in rice noodle fermentation: A metagenomic and untargeted metabolomic...

Inoculated fermentation accelerates rice noodle production and improves quality, but the underlying microbe-metabolite dynamics remain unclear. This study employed metagenomic and non-targeted metabolomic profiling to investigate microbial succession and metabolic transformations during fermentation. Lacticaseibacillus rhamnosus, Lactococcus cremoris, and Saccharomyces cerevisiae were identified as dominant strains, with Lacticaseibacillus rhamnosus rapidly outcompeting other microbes and suppressing Klebsiella pneumoniae and Salmonella enterica by over 70 %. At 6 h, rice noodle hardness and springiness improved markedly, driven by microbial shifts and metabolic outputs. Metabolomic analysis identified 1405 metabolites, of which 57 showed significant changes: aspartic and citric acid levels declined by 14.99 % and 33.16 %, while citrulline, γ-aminobutyric acid, lactate, and Cinnamic acid increased by 16.38 %, 8.96 %, 70.69 %, and 63.90 %, respectively. Enzyme annotation indicated α-amylase and glycogen synthase regulate starch degradation and amylose synthesis. These findings provide insights into the microbial and metabolic mechanisms that enhance the quality of fermented rice noodles.