Optimization And Composition Analysis For The Production Of α-glucosidase Inhibitors By Bacillus Amyloliquefaciens SY07

Diabetes mellitus, a metabolic disorder characterized by chronic hyperglycaemia and accompanied with a number of severe complications, is the third threat that seriously harms mankind health behind cardiovascular disease and cancer. Seeking for the hypoglycemic functional factors with high efficiency has become the focus of research. a-Glucosidase inhibitor is an effective approach to the management of non-insulin-dependent diabetes, by suppressing oligosaccharide hydrolysis and thus reducing postprandial carbohydrate uptake.This work aims at screening and identifying a new a-glucosidase inhibitor-producing bacterial strain,and analysing the physical and chemical characteristics as well as the separation of the a-glucosidase inhibitors. The main results are described as below:Compared to samples started with Bacillus subtilis natto, Aspergillus oryzae,Aspergillus niger and Monascus, fermented soybean sample started with the bacterial strain SY07 exhibited potent inhibition on a-glucosidase. This strain was identified as Bacillus amyloliquefaciens SY07 based on its 16S rRNA gene and gyrB gene sequences as well as morphological, physiological and biochemistry properties.The optimized fermentation conditions for B. amyloliquefaciens SY07 to produce a-glucosidase inhibitors were as follows: okara 5%, inoculation amount 2%, medium capacity 60 mL/250 mL, initial pH 6.5, 180 r/min of shaking speed, temperature 37℃, and 48 h of fermentation time. The a-glucosidase inhibitory activity of the fermented sample under such conditions reached to 60.08%, which was 13.01% higher than before (47.07%).The fermented sample presented a reversible, uncompetitive pattern on a-glucosidase inhibition. The active components were stable at a large range of temperature or acid-base environment and showed rather high polarity. Preliminary chemical analysisshowed possible presence of carbohydrates in the active components.Using dialysis and Sephadex G-15, the a-glucosidase inhibitors in final fermented product were preliminarily purified. An active fraction was obtained, with an IC50 value of 0.056 mg/mL which is close to that of acarbose,a commercial hypoglycemic drug. Further reseach on the active compounds generated by B. amyloliquefaciens SY07 would be of great significance.