Exploring the microbiota and metabolites of traditional rice beer varieties of Assam and their functionalities

Abstract

Rice beer is traditionally prepared and consumed by various ethnic populations in the Southeast Asian countries. To understand the probable effects of rice beer on human health, present research was aimed to study biochemical parameters, microbial diversity and metabolites of major rice beer varieties of Assam, namely Apong (Poro and Nogin), Xaaj and Joubishi. Alcoholic content of rice beer varieties varied from 9.41 to 19.33% (v/v). Free radical scavenging activity against DPPH• and ABTS + were 1.94-4.14 and 1.69-3.91 mg of ascorbic acid/ml of rice beer, respectively. In relation to antioxidant activities, phenolic content varied from 2.07 to 5.40 mg gallic acid/ml of rice beer. Next-generation sequencing of 16S rDNA showed that 18 genera of bacteria were present irrespective of rice beer varieties in which lactic acid bacteria were the dominant group (90% abundance). Functional predictions based on the bacterial profiles indicated pathways, such as metabolisms of carbohydrate, amino acid, vitamins and cofactors, and xenobiotic biodegradation, to be active in the rice beer varieties. Out of 18 core bacterial genera, 7 had correlations with the predicted functions. Gas chromatography and mass spectroscopy-based metabolite analysis revealed that the metabolite profiles of the rice beer varieties consisted of 18 saccharides, 18 organic acids, 11 sugar alcohols, 8 amino acids, 1 vitamin and nutraceutical compounds thiocoumarine, carotene, oxazolidine-2-one and acetyl tyrosine. Due to the presence of potent prebiotics, probiotics and nutraceuticals, rice beer may have health benefits which need to be studied further.

A Big World in Small Grain: A Review of Natural Milk Kefir Starters

“…Johansen et al reviewed the functions of several quorum sensing (QS) (mediation of microbial cell-cell communication by secretion or recognition of small signal molecules) systems to regulate microbial traits in food-related communities and the potential effects on the quality of fermented products [49]. QS has been studied for several microorganisms involved in the production of fermented vegetables, sourdough, wine and some dairy products [50][51][52][53]. Although there are recent studies about the analysis of the metabolites profile of milk kefir [54][55][56], there is no thorough study to investigate the signaling functions of such metabolites on kefir-related species.…”

Deep microbial community profiling along the fermentation process of pulque, a biocultural resource of Mexico

“…Some Coprococcus ferment mucins, plant-derived carbohydrates into butyric, acetic, formic, propionic, and lactic acids (Holdeman and Moore, 1974;Salyers et al, 1977). Recently, it has been reported Neoasia does participate in rice beer production (Das et al, 2019). On the other hand, Bdellovibrio has the ability to predate other Gram-negative bacteria, suggesting that it could regulate the presence of probably pathogenic bacteria in pulque, Bdellovibrio has also been isolated from the fermentation of Chinese rice wine, and reported to be plant-associated (Martínez et al, 2016;Jialiang et al, 2018;Alcaraz et al .…”

Traditionally brewed rice beverage alters gut microbiota and metabolites in mice

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