A novel raw starch digesting thermostable α-amylase from Bacillus sp. I-3 and its use in the direct hydrolysis of raw potato starch

• Published in: Enzyme and microbial technology 2005-12, Vol.37 (7), p.723-734
• Main Authors: Goyal, Nidhi, Gupta, J.K., Soni, S.K.
• Format: Article
• Language: English
• Subjects: Bacillus sp; Biological and medical sciences; Biotechnology; Direct hydrolysis; Fundamental and applied biological sciences. Psychology; Raw potato starch; Raw starch adsorption; Raw starch hydrolysis; Thermostable α-amylase
• ISSN: 0141-0229; 1879-0909
• DOI: 10.1016/j.enzmictec.2005.04.017

A new strain of Bacillus sp. I-3, isolated from natural soil samples, showed a high raw starch digesting activity towards potato starch. Upon optimization of various environmental and cultural conditions, the yield of α-amylase reached 642 U/mL. The kinetic characterization of partially purified enzyme exhibited the maximum activity at 70 °C, pH 7.0 and revealed a high thermostability in the presence of 10 mM CaCl 2·2H 2O where it could retain more than 90% residual activity at 70 °C after 3.5 h. At 80, 90 and 100 °C, the enzyme retained 80, 59 and 26% of its maximum activity after 2.5, 0.5 and 0.5 h, respectively. The enzyme preparation had a strong affinity towards raw potato starch granules and was almost completely adsorbed onto it. It also hydrolyzed raw potato starch at a concentration of 12.5% significantly in a short period of time of 12 h.