Deciphering microbial diversity and predicting metabolic functionalities in fermented pigmented rice water using...

Fermented rice water is gaining importance lately due to its traditional food culture and potential beneficial effects. Flavored fermented rice water (FFRW) produced from pigmented rice varieties, viz., black, brown, and red, is shown to have rich nutritional and functional profiles. However, the microbiota in this spontaneously fermented beverage is scantly known. Hence, this study aimed to explore the total bacterial and fungal diversity using 16S rRNA and Internal Transcribed Spacer (ITS) sequencing, respectively, along with the phytochemicals and their metabolites produced/utilized during storage. The bacterial diversity showed significant differences (p < 0.05) in black FFRW while depicting stability for brown- and red-FFRW on the 0th day and 30th day of refrigerated storage. Lactic acid bacteria (LAB) like Weissella were abundantly recorded; similarly, fungal diversity showed dominance of various yeasts. Predictive functional/metabolic pathways suggested 23 pathways of which the predominant were metabolism amino acids like branched-chain amino acids (BCAAs) viz., leucine, valine, and isoleucine, aromatic amino acids such as tryptophan, and metabolites of glycan biosynthesis, polyphenols, lipids, cofactors and vitamins. KEGG pathways revealed a shift in microbial metabolism from amino acid degradation pathways dominating on day 0 to carbohydrate and fatty acid metabolism by day 30. Enzymes like lactate dehydrogenase showed increased abundance by the 30th day, particularly in red and black-FFRW. The untargeted profiling showed that brown FFRW had more polyphenol-related compounds, followed by black and red FFRW. Decrements in the compounds were detected on the 30th day of storage compared to the 0th day. The findings provide insights into the microbial diversity, metabolic potential, and phytochemical composition of FFRW, supporting its potential as a functional beverage.