A bottom-up strategy for constructing a synthetic microbiome and its application to the design of Pixian Douban starter

Abstract:

[Objective] This study aimed to construct a synthetic microbiome which would be used as a starter for Pixian Douban (broad bean paste) fermentation.[Methods] We analyzed core microorganisms of Pixian Douban fermentation by the combined indicators,including microbial relative abundance,frequency and eigenvector centrality.Then a fully synthetic medium which simulated the in situ fermentation system was designed and used to explore the growth and aroma-producing characteristics of core microorganisms.According to the complementary aroma-producing characteristics of core microorganisms,a two-strain co-fermentation experiment was conducted.Moreover,taking the microbial interactions into account,we designed a three-strain community and verified its fermentation performance.[Results] In this study,9 microorganisms were identified and isolated from Pixian Douban as the core microorganisms.Then the volatile profiles of these core microorganisms were detected and a complementary aroma-producing relationship was found among yeasts,lactic acid bacteria and other microorganisms.Combining the growth inhibition relationship among microorganisms,we formed a three-strain combined inoculum,including Pediococcus acidilactici,Staphylococcus carnosus and Candida versatilis.With the three-strain community as the fermentation starter,the fermentation samples showed 63.1% similarity of flavor compounds and 21.8% improvement of amino acid nitrogen content compared to the in situ samples.[Conclusion] A bottom-up strategy for constructing a synthetic microbiome community was proposed,and a three-strain microbial community as the starter for Pixian Douban production was built.This study is valuable for synthetic microbiome construction and fermentation process optimization.