Identification a Novel Raw-Starch-Degrading-a-Amylase from a Tropical Marine Bacterium

摘要

Problem statement: Bacteria from the surface of the tropical marine hard coral Acropora sp. were screened for producing raw-starch-degrading-a-amylase. Approach: Based on its 16s rDNA sequence, a bacterium that produced the highest amylolitic activitywas identified as Bacillus amyloliquifaciens ABBD. The bacterial isolate secreted a a-amylase extracellularly and then the enzyme was partially purified by ammonium sulfate precipitation followed by anion exchange chromatography. Results: Electrophoresis results both SDS-PAGE and native PAGE suggested that the enzyme was a heterodimeric protein (97 kDa) consisting of 45 and 55 kDa subunits. The a-amylase had an optimum pH of 7.0 and temperature of 60°C. More than 80% activity of the enzyme was retained under high salt conditions (up to 20% NaCl). The enzyme remained stable at 50°C for 1 h. Starch hydrolysis by the enzyme at 70°C yielded oligosaccharides (G2-G4) and at room temperature yielded glucose/maltose (Gl and G2). Conclusion: The B. amyloliquifaciens ABBD a-amylase was capable of degrading various raw starch granules from corn, rice, cassava and sago at room temperature.