Investigation of Extracellular Highly Thermostable Starch Hydrolyzing Activity from A Novel Thermophilic Bacterium Anoxybacillus gonensis A4

摘要

A novel hot spring thermophile, Anoxybacillus gonensis A4 was investigated in terms of capability of starch degradation and characterization of its thermostable hydrolytic activity. It was observed that A. gonensis A4 has a hydrolytic enzyme responsible for starch hydrolysis with a 0.6 R_f value. The extracellular crude preparation was characterized in terms of pH and temperature optima and stabilities, kinetic parameters and inhibition/activation behaviour toward some chemicals and metal ions. Starch agar assay showed that A. gonensis A4 secreted a hydrolytic enzyme and K_m and V_(max) values of its activity were found to be 1.88 mg/ mL and 0.54 U/mg protein, respectively. The optimum temperature and pH, for A. gonensis A4 hydrolase was 30 °C and 7.5, respectively. The enzyme activity was not significantly changed by incubating crude extract solution at the temperature range from 20 to 80 °C for 60 h. pH-stability profile of the crude enzyme for 24 h at 4 °C of incubation temperature showed that the enzyme had good stability over 65 % at all investigated pH range from 4.5-9.5. The efficiency of metabisulphite on crude amylolytic activity indicated that A. gonensis A4 produce a hyrolaze having disulfide bridges were essential for starch hydrolysis.