Antioxidant capacities of Bacillus endophyticus ST-1 and Ketogulonicigenium vulgare 25B-1 in vitamin C fermentation

Abstract

ABSTRACTKetogulonicigenium vulgare and Bacillus play an important role in the two-step fermentation of vitamin C. Resolving the interaction between the two strains, not only can reduce the production cost and improve the productivity gains of vitamin C, but also can give significant clues for the study of complex microbial consortia. We analyzed some physiological properties, antioxidant-related enzyme activities and gene expression patterns of Bacillus endophyticus ST-1 and Ketogulonicigenium vulgare 25B-1 in vitamin C mono- and co-culture fermentation systems before and after B. endophyticus ST-1 sporulation. B. endophyticus ST-1 accelerated the growth and caused excessive accumulation of reactive oxygen species in K. vulgare 25B-1, resulting in oxidative stress. Oxidative stress signals could be transmitted to B. endophyticus ST-1, resulting in the upregulation of sodA, katE and gp genes, which are related to oxidation resistance and regulation of the oxidation–reduction state. The release of spores and the lysis of B. endophyticus ST-1 cells provided a favourable oxidation–reduction state for K. vulgare 25B-1 growth. The expression of sodB, grxC, gor and zwf genes in K. vulgare 25B-1 was gradually upregulated, leading to increased antioxidant capacity. B. endophyticus ST-1 regulates the oxidation–reduction state in the vitamin C fermentation system, thereby enhancing the antioxidant capacities of K. vulgare 25B-1.