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

This study reports the microbial quality of ethnic starter culture Xaj-pitha used for rice wine fermentation in Assam. Here, we collected 60 Xaj-pitha samples belonging to Ahom 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 Acidovorax, Herbaspirillum, Methylobacterium, Pantoea, Pseudomonas, Stenotrophomonas, Staphylococcus, Micrococcus, Acinetobacter, 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., Penicillium sp. ABTSJ23, Rhizopus oryzae ABTSJ63, Mucor guilliermondii ABTSJ72 and Amylomyces rouxii ABTSJ82 and eight yeasts viz., Saccharomyces cerevisiae ABTY1J, ABTY1S, ADJ5 & ADJ1, Wickerhamomyces anomalus ADJ2, Saccharomycopsis malanga ADJ3, Saccharomycopsis fibuligera ADJ4 and Saccharomycopsis malanga ADJ6 were retrieved using appropriate media. All the mould cultures tested negative for aflotoxins production. Among the yeasts, Saccharomyces cerevisiae ABTY1S and ADJ1 decarboxylated lysine HCl and tyramine HCl, respectively, indicating their biogenic amine production ability. For defined mixed starter culture, Amylomyces rouxii ABT82 with α-amylase (5.92 U/ml) and glucoamylase (7.50 U/ml) activities was selected as fungal partner; while Saccharomycopsis fibuligera ADJ4 and Saccharomyces cerevisiae 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.

Metagenomics analysis of microbial communities associated with a traditional rice wine starter culture (Xaj-pitha) of Assam, India.

This is the first report on the microbial diversity of xaj-pitha, a rice wine fermentation starter culture through a metagenomics approach involving Illumine-based whole genome shotgun (WGS) sequencing method. Metagenomic DNA was extracted from rice wine starter culture concocted by Ahom community of Assam and analyzed using a MiSeq® System. A total of 2,78,231 contigs, with an average read length of 640.13 bp, were obtained. Data obtained from the use of several taxonomic profiling tools were compared with previously reported microbial diversity studies through the culture-dependent and culture-independent method. The microbial community revealed the existence of amylase producers, such as Rhizopus delemar, Mucor circinelloides, and Aspergillus sp. Ethanol producers viz., Meyerozyma guilliermondii, Wickerhamomyces ciferrii, Saccharomyces cerevisiae, Candida glabrata, Debaryomyces hansenii, Ogataea parapolymorpha, and Dekkera bruxellensis, were found associated with the starter culture along with a diverse range of opportunistic contaminants. The bacterial microflora was dominated by lactic acid bacteria (LAB). The most frequent occurring LAB was Lactobacillus plantarum, Lactobacillus brevis, Leuconostoc lactis, Weissella cibaria, Lactococcus lactis, Weissella para mesenteroides, Leuconostoc pseudomesenteroides, etc. Our study provided a comprehensive picture of microbial diversity associated with rice wine fermentation starter and indicated the superiority of metagenomic sequencing over previously used techniques.