ZHANG Yan, ZHAO Xinqi, WANG Tianqi, WANG Cheng, YU Bing, LYU Jialu, ZHANG Lili, XU Yunhe
To understand the main metabolic substrates, metabolic pathways, accumulated products and byproducts of mixed fermentations of corn, two lactic acid bacteria strains were used as mixed fermentation starters to ferment corn beverages and byproducts. The low molecular weight substance content before and after beverage fermentation was assessed and compared using non-targeted metabolomics technology. Significant differences in metabolites were observed between the pre-fermented corn and its fermentation product beverage. Fourteen differential metabolites were identified, including three nucleotides and their derivatives, two organic acids, two amino acids and their derivatives, two flavonoids, one phenylpropionic acid, one antibiotic, one nicotinamide, one naphthol derivative, and one phosphate methyl alcohol. These included multiple potentially beneficial activities: 1-hydroxy-2-naphthoic acid, a naphthol with anti-inflammatory activity, isopentene, which has anti-bacterial, hypotensive, anti-fungal, anti-oxidant, anti-HIV, anti-tumor, and other effects, and epicatechin, which has the function of anti-oxidation, prevention and cure to heart and cerebrovascular, and can prevent the epicatechin of tumor, etc. Metabolic pathway analysis via KEGG revealed five metabolic pathways significantly involved in fermentation, including valine, leucine and isoleucine biosynthesis, tyrosine metabolism, two-component system, purine metabolism, and the citric acid cycle. These studies confirmed that lactic acid bacteria fermentation could promote synthesis and accumulation of useful metabolites as byproducts of corn-based beverage fermentation, and provide a reference for the comprehensive evaluation of the utilization of lactic acid bacteria in fermented cereal beverage production.
