Abstract
Bacillus velezensis LPL061, which shows strong exopolysaccharide (EPS) producing capacity, was isolated from carnations in Beijing, China. The complete genome of LPL061 comprised a single circular chromosome (3,907,268 bp; G+C content of 46.7%) with 3,737 coding DNA sequences, 26 rRNA, and 89 tRNA. According to genome analysis, 12 protein-coding genes which related to polysaccharide biosynthesis in LPL061 were identified. Comparative genome analysis revealed that the EPS biosynthetic gene cluster was relatively conserved among Bacillus species. EPS showed approximately 60% inhibitory activity on the α-glucosidase at 100 μg/mL. The results of quantitative reverse transcription PCR further demonstrated that compared to insulin-resistant model with insulin (500 μg/mL) (without EPS treatment), the insulin-resistant HepG2 cells treated with EPS decreased the expression of phosphoenolpyruvate carboxykinase (PEPCK) from 4.425 to 0.1587, glucose-6-phosphatase (G6Pase) decreased from 4.272 to 0.1929, and glycogen synthase kinase3β (GSK(3)β) decreased from 2.451 to 0.993, respectively. Meanwhile, EPS treatment increased GS expression and resulted in intracellular glycogen concentration increased from 28.30% to 86.48%, which further supported that EPS form LPL061 could reduce the concentration of blood glucose effectively. These results could be beneficial for better understanding of the hypoglycemic mechanism of B. velezensis LPL061 EPS and developing an EPS-based anti-diabetic agent in the future.