Assessment of microbial quality and health risks associated with traditional rice wine starter of Assam, India: a step towards defined and controlled fermentation.

This study reports the microbial quality of ethnic starter culture used for rice wine fermentation in Assam. Here, we collected 60 samples belonging to community of the state and enumerated the microorganisms using spread plate technique. Illumina-based whole genome shotgun sequencing detected the presence of microbial contaminants like , , , , , , , , , etc. Presence of major health hazards associated with spontaneous rice wine fermentation necessitated method optimization through the development of a defined mixed starter culture. For this, functionally important α-amylase producers viz, sp. ABTSJ23, ABTSJ63, ABTSJ72 and ABTSJ82 and eight yeasts viz, ABTY1J, ABTY1S, ADJ5 & ADJ1,  ADJ2, ADJ3, ADJ4 and ADJ6 were retrieved using appropriate media. All the mould cultures tested negative for aflotoxins production. Among the yeasts, ABTY1S and ADJ1 decarboxylated lysine HCl and tyramine HCl, respectively, indicating their biogenic amine production ability. For defined mixed starter culture, ABT82 with α-amylase (5.92 U/ml) and glucoamylase (7.50 U/ml) activities was selected as fungal partner; while ADJ4 and ABT-Y1J with high ethanol production (up to 10.11% and 9.88% v/v, respectively) were selected as yeast partners. The mixed culture was able to produce high amount of glucose, ethanol and liquid (glucose 10.91% w/v; ethanol 7.5% w/v; liquid 51.0% w/v). Therefore, this study demonstrated the efficiency of mixed starter cultures for safe and controlled rice wine production.