Saccharomyces cerevisiae is a representative yeast used for alcohol production. Production of alcohol from milk using S. cerevisiae is not easy, as this species is unable to hydrolyse lactose. Lactobacillus delbrueckii subsp. bulgaricus (LDB) is able to hydrolyse lactose into galactose and glucose, and is widely used in yogurt production. In this study, production of alcohol from milk was attempted by multiple fermentation using S. cerevisiae and LDB. Firstly, strain LDB48A-12, released from catabolite repression, was obtained from LDB48P by N-methyl-N ’-nitro-N-nitrosoguanidine mutagenesis. LDB48A-12 showed high ability of lactose degradation. Surprisingly, growth speed and lactate production of LDB48A-12 were found to be lower than those of LDB48P. Fermentation of 10% skim milk solution using LDB48A-12 and S. cerevisiae SBC3207 for 4 days at 30℃ or 37℃ produced approximately 1~1.5% of alcohol, which was 1.5 times that produced using LDB48P. In addition, decrease in pH was inhibited. These results were thought to demonstrate novel alcoholic milk fermentation. Comparison of genome sequences revealed mutations in RpoA and DnaA in LDB48A-12. These genes are related to catabolite repression and replication of genome DNA, respectively, suggesting that combined mutation of these genes leads to the preferable phenotype for alcoholic milk fermentation.
We investigated the effects of heat-killed Lactobacillus paracasei K71 (K71）on lipid metabolism and gut microbiota in an ob/ob mouse model of obesity. Wild-type and ob/ob (ob-AIN group) mice were fed an AIN-93G diet or an AIN 93G diet containing K71 (ob-K71 group) for 90 d. Serum lipids, hepatic gene expression, and gut microbial populations were evaluated. K71 intake had no significant effect on body weight or lipid metabolism in the liver, while serum nonesterified fatty acids (NEFA) were lower in the ob-K71 group than in the ob-AIN group. In addition, the expression of serine palmitoyl transferase (SPT)-1, a key enzyme in the formation of ceramides associated with insulin resistance, was also lower in the livers of the ob-K71 group than in those of the ob-AIN group. Sequencing of the 16S ribosomal RNA gene revealed that K71 intake suppressed the changes in gut microbiota related to type 2 diabetes and nonalcoholic steatohepatitis. Our results suggest that K71 ingestion alters gut microbiota composition and improves insulin resistance via the ceramide synthesis pathway.