AUTHOR=Chai Li-Juan , Lu Zhen-Ming , Zhang Xiao-Juan , Ma Jian , Xu Peng-Xiang , Qian Wei , Xiao Chen , Wang Song-Tao , Shen Cai-Hong , Shi Jin-Song , Zheng-Hong Xu 

TITLE=Zooming in on Butyrate-Producing Clostridial Consortia in the Fermented Grains of Baijiu via Gene Sequence-Guided Microbial Isolation

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01397

DOI=10.3389/fmicb.2019.01397

ISSN=1664-302X

ABSTRACT=<p>Butyrate, one of the key aroma compounds in Luzhou-flavor <italic>baijiu</italic>, is synthesized through two alternative pathways: butyrate kinase (<italic>buk</italic>) and butyryl-CoA: acetate CoA-transferase (<italic>but</italic>). A lack of knowledge of butyrate-producing microorganisms hinders our ability to understand the flavor formation mechanism of <italic>baijiu</italic>. Here, temporal dynamics of microbial metabolic profiling in fermented grains (FG) was explored <italic>via</italic> PICRUSt based on 16S rRNA gene sequences. We found Bacilli and Bacteroidia were the major potential butyrate producers in <italic>buk</italic> pathway at the beginning of fermentation, while later Clostridia dominated the two pathways. Clone library analysis also revealed that Clostridia (~73% OTUs) was predominant in <italic>buk</italic> pathway throughout fermentation, followed by Bacilli and Bacteroidia, and <italic>but</italic> pathway was merely possessed by Clostridia. Afterward, Clostridia-specific 16S rRNA gene sequencing demonstrated <italic>Clostridium</italic> might be the major butyrate-producing genus in two pathways, which was subsequently evaluated using culture approach. Seventeen <italic>Clostridium</italic> species were isolated from FG based on 16S rRNA gene sequence-guided medium prediction method. Profiles of short-chain fatty acids and <italic>but</italic> and <italic>buk</italic> genes in these species demonstrated phylogenetic and functional diversities of butyrate-producing <italic>Clostridium</italic> in FG. These findings add to illustrate the diversity of potential butyrate producers during brewing and provide a workflow for targeting functional microbes in complex microbial community.</p>