Investigating the probiotic and flavor-producing functions of Bacillus sp. FPIK1 sourced from fermented bamboo shoots of Assam.

BACKGROUND: Fermented bamboo shoots, locally known as Khorisa, are a traditional food widely consumed in Assam, India, valued for their distinctive tangy flavour and potential probiotic benefits. This study aimed to isolate, identify, and characterize microbial strains from Khorisa, assessing their probiotic potential, safety, and flavour-producing capabilities for application in functional food products. METHODS: Fifteen Khorisa samples were collected from five districts of Assam. Fifty-two microbial isolates were obtained and screened for proteolytic, lipolytic, and carbohydrate-fermenting activities. Six strains (Khorisa/NA/1-Khorisa/NA/6) showing positive enzymatic activity were evaluated for safety (haemolysis, DNase activity, antibiotic susceptibility) and probiotic attributes, including acid, bile, salt, and phenol tolerance, auto-aggregation, and epithelial cell adhesion. Sensory evaluation of curd and rice beverage fermented with these isolates was performed by a trained panel. Derivatized compounds were profiled using gas chromatography-mass spectrometry (GC-MS). Molecular identification was conducted via 16 S rRNA sequencing. RESULTS: Strain Khorisa/NA/3 was identified as Bacillus sp. strain FPIK1. It exhibited outstanding probiotic-like potential, maintaining 59.2% survival at pH 2, 92.5% at pH 4, and 40% bile salt tolerance. It demonstrated notable halotolerance (20.6% viability at 8% NaCl), phenol resistance (97% at 0.4%), high auto-aggregation (29%), and strong epithelial adhesion (69%). Thermal adaptability was evident with 91.5% viability at 37 °C and 83.4% at 40 °C. Safety evaluation confirmed a non-haemolytic, DNase-negative phenotype with broad antibiotic susceptibility, showing resistance to only one tested antibiotic. Sensory trials revealed that curd and rice beverage fermented with FPIK1 achieved the highest scores for flavour, aroma, and overall acceptability. GC-MS profiling revealed a diverse array of esters, alcohols, ketones, and organic acids that imparted sweet and lemony-sour notes. These volatiles were absent in both uninoculated controls and products prepared with non-flavour-producing strains, underscoring the strain's inherent ability to enhance organoleptic quality through natural flavour biosynthesis. CONCLUSION: Bacillus sp. FPIK1, isolated from traditional Khorisa, combines robust probiotic-like attributes, a favourable safety profile, and diverse flavour-producing capabilities, underscoring its suitability as a natural starter culture for probiotic-like, flavour-enhanced fermented foods. These findings support its potential incorporation into functional dairy and non-dairy products, offering both sensory and health benefits while valorizing an indigenous fermented food resource.