Community structure and metabolic potentials of the traditional rice beer starter 'emao'

Impact of Incorporating Shiitake Mushrooms (Lentinula edodes) on Microbial Community and Flavor Volatiles in Traditional Jiuqu

Jiuqu is one of the important raw materials for brewing Chinese rice wine (Huangjiu), often known as the "bone of wine". In this study, the microbial community and flavor substances of Jiuqu made with different amounts of shiitake mushroom (Lentinula edodes) were investigated through high-throughput sequencing technology and headspace gas chromatography-ion migration spectroscopy (HS-GC-IMS), using traditional wheat yeast as a control. The results showed that 1593 genera and 5507 species were identified among the four types of yeast, with Aspergillus and Paecilomyces being the most dominant microorganisms at the genus level. Carbohydrate, coenzyme, and amino acid metabolism may be the main metabolic processes of the dominant microorganisms in Jiuqu. In terms of flavor, a total of 79 volatile substance monomers and some dimers were detected from four types of Jiuqu raw materials, with the main substances being 12 aldehydes, 19 ketones, 13 alcohols, 19 esters, 4 olefins, 1 acid, 3 ethers, 4 furans, 1 pyrazine, 1 pyridine, 1 triethylamine, and 1 thiazole. The correlation results indicate that Aspergillus, Lactobacillus, and Vibrio correlate significantly with the volatile flavor compounds unique to shiitake mushrooms and also have a positive effect on alcohol, esters, and furans. These results could shed light on the selection of Lentinula edodes as a fermentation starter for Huangjiu in the Qinba Mountain area.

Unveiling the microbial communities and metabolic pathways of Keem, a traditional starter culture, through whole-genome sequencing

Traditional alcoholic beverages have played a significant role in the cultural, social, and culinary fabric of societies worldwide for centuries. Studying the microbial community structure and their metabolic potential in such beverages is necessary to define product quality, safety, and consistency, as well as to explore associated biotechnological applications. In the present investigation, Illumina-based (MiSeq system) whole-genome shotgun sequencing was utilized to characterize the microbial diversity and conduct predictive gene function analysis of keem, a starter culture employed by the Jaunsari tribal community in India for producing various traditional alcoholic beverages. A total of 8,665,213 sequences, with an average base length of 151 bps, were analyzed using MG-RAST. The analysis revealed the dominance of bacteria (95.81%), followed by eukaryotes (4.11%), archaea (0.05%), and viruses (0.03%). At the phylum level, Actinobacteria (81.18%) was the most abundant, followed by Firmicutes (10.56%), Proteobacteria (4.00%), and Ascomycota (3.02%). The most predominant genera were Saccharopolyspora (36.31%), followed by Brevibacterium (15.49%), Streptomyces (9.52%), Staphylococcus (8.75%), Bacillus (4.59%), and Brachybacterium (3.42%). At the species level, the bacterial, fungal, and viral populations of the keem sample could be categorized into 3347, 57, and 106 species, respectively. Various functional attributes to the sequenced data were assigned using Cluster of Orthologous Groups (COG), Non-supervised Orthologous Groups (NOG), subsystem, and KEGG Orthology (KO) annotations. The most prevalent metabolic pathways included carbohydrate, lipid, and amino acid metabolism, as well as the biosynthesis of glycans, secondary metabolites, and xenobiotic biodegradation. Given the rich microbial diversity and its associated metabolic potential, investigating the transition of keem from a traditional starter culture to an industrial one presents a compelling avenue for future research.

Amylolytic Fungi in the Ethnic Beer Starter “emao” and Their Beer-Producing Attributes

Naturally occurring autochthonous microbes associated with ethnic beer starters are diverse and important as they play different functional roles in beer fermentations. The study on culturable microbes from the ethnic rice beer starter “emao” of the Bodo community of Assam is limited. Here we isolated and identified the culturable fungal diversity associated with emao and screened them for beer-producing capability from glucose and starch substrates. Based on morphology and molecular characterization, the species identified were Candida glabrata (Cgla_RF2), Cyberlindnera fabianii (Cfab_RF37), Hyphopichia burtonii (Hbur_RF19), Mucor circinelloides (Mcir_RF48), Mucor indicus (Mind_RF25), Penicillium citrinum (Pcit_RF32), Rhodosporidiobolus ruineniae (Rrui_RF4 & Rrui_RF43), Saccharomyces cerevisiae (Scer_RF6), Saccharomycopsis fibuligera (Sfib_RF11), and Wickerhamomyces anomalus (Wano_RF3) among which the relative abundance (RA) of W. anomalus was the highest (24%) followed by C. glabrata and H. burtonii (16% in each). Five (Hbur_RF19, Sfib_RF11, Mind_RF25, Mcir_RF48, and Pcit_RF32) of eleven isolates showed amylase positive in the starch medium. Scer_RF6 showed the highest ethanol tolerance (14% v/v) followed by Hbur_RF19 (12% v/v), Cgla_RF2 (11% v/v) and Wano_RF3 (11% v/v). The amylase-positive strains produced beer-containing ethanol in the range of 3.17–7.3 (% v/v) from rice substrate. Although the rice beer produced by amylase-positive strains showed negligible pH difference, other parameters like ethanol, ascorbic acid, total phenol, and antioxidant properties were varied from beer to beer. Antibacterial activities shown by Mcir_RF48 and Pcit_RF32 against the test bacteria were higher with a 23–35 mm zone of inhibition than the other isolates. The present findings reveal the presence of fungi with antibacterial, amylolytic, ethanol fermenting, and antioxidant producing capacity in emao which could the source for future bioprospection.