Microbial diversity and probiotic potential of fermented traditional rice varieties: Characterization and functional evaluation

This study focuses on the characterization of probiotic diversity derived from two
fermented traditional rice varieties, Kattuyanam and Mappillai Samba. The rice samples
were processed, lyophilized, and subjected to microbiological analysis. Molecular
identification was performed using metagenomics analysis. Probiotic efficacy was
evaluated through acid and bile salt tolerance tests, antibiotic susceptibility assays (agar
well diffusion), glucose fermentation, and adhesion assays on stainless steel plates.
Metagenomic analysis confirmed the dominance of the Firmicutes phylum in both
samples, with Lactobacillaceae as the most prevalent family. Antibiotic susceptibility
tests revealed varying resistance patterns, with notable resistance to penicillin,
streptomycin, and ampicillin, while susceptibility to tetracycline, rifampin, and
erythromycin varied between samples. The combination of rice varieties displayed
increased susceptibility compared to individual strains. In vitro probiotic efficacy tests
demonstrated acid and bile salt tolerance, with the Kattuyanam and Mappillai Samba 1:1
(KRMR) showing the highest survival rates under acidic (80.287±0.328%) and bile salt
(78.419±0.285%) conditions. Glucose fermentation tests indicated homofermentative
behavior in all isolates, producing lactic acid without gas accumulation. Additionally,
adhesion assays revealed that KRMR had the highest adherence to stainless steel
(39.333±1.52%), indicating its potential for gut colonization. These findings highlight
the probiotic potential of traditional rice-fermented microbes for applications in
gastrointestinal health and functional foods.