Effect of Lactobacillus plantarum-fermented mulberry pomace on antioxidant properties and fecal microbial community

Rich in phenolic compounds and dietary fibers, mulberry pomace is a potential material for gut health. This study investigated the effect of the probiotic Lactobacillus plantarum on mulberry pomace. The antioxidant activity as well as the changes of fecal microbiota and short-chain fatty acids (SCFAs) were determined using chemical models, quantitative polymerase chain reaction (qPCR) and gas chromatography, respectively. Furthermore, the phenolic compounds were characterized by UPLC-MS. The results showed that the antioxidant activity was significantly improved in fermented mulberry pomace (FMP) samples. The fecal microbiota community was modulated by FMP through improving beneficial bacteria (Lactobacillus, Bifidobacterium, Ruminococcus, butyrate-producing bacteria and Akkermansia) and inhibiting pathogenic bacteria (Escherichia coli and Enterococcus). Moreover, FMP showed an increase in the production of SCFAs and lactic acid. The study identified that the corresponding glycosides of cyanidin and quercetin were released during Lactobacillus plantarum fermentation. A total of eighteen phenolic compounds were detected in samples and three compounds (p-hydroxybenzoic acid, catechin and gallocatechin) were only detected in FMP samples. The changes in phenolic compounds might explain the gut-improving functions. This study provided a suggestion that Lactobacillus plantarum fermentation was a potential way to utilize mulberry pomaces as a functional food.