Effect of methylcobalamin-C-10-Br from stinky tofu on inhibition of Listeria monocytogenes and alteration of microbiota in an in vitro colonic simulation

Abstract

In this study, it was found that methylcobalamin-C-10-Br (MeCbl-C-10-Br) from stinky tofu exerts an inhibitory effect on Listeria monocytogenes, and the minimum inhibitory concentration was 0.125 ng/mL. Here, we studied the effect of MeCbl-C-10-Br on the adenosylcobalamin (AdoCbl)-dependent enzyme glycerol dehydratase, the methylcobalamin (MeCbl)-dependent enzyme methionine synthetase and three types of vitamin B12 riboswitches from L. monocytogenes. The results show that MeCbl-C-10-Br inhibits about 100% of glycerin dehydrase activity and about 37% methionine synthase activity. While the expression of the downstream genes of the vitamin B12 riboswitch is suppressed, the ratios of inhibition of transport, synthetic, and functional vitamin B12 riboswitches from 1.00 μg/mL MeCbl-C-10-Br are approximately 60%, 30%, and 40%, respectively, which suggests that MeCbl-C-10-Br effectively controls the growth of L. monocytogenes. According to the results of the simulated fermentation, MeCbl-C-10-Br did not destroy the balance of intestinal microbes after ingestion, which indicates that MeCbl-C-10-Br is a safe antibacterial agent and can be applied to food in the future.