Production and characterization of a thermostable α-amylase from Nocardiopsis sp. endophyte of yam bean

Thermostable amylolytic enzymes have been currently investigated to improve industrial processes of starch degradation. Studies on production of α-amylase by Nocardiopsis sp., an endophytic actinomycete isolated from yam bean (Pachyrhizus erosus L. Urban), showed that higher enzyme levels were obtained at the end of the logarithmic growth phase after incubation for 72 h at pH 8.6. Maximum activity of α-amylase was obtained at pH 5.0 and 70°C. The isolated enzyme exhibited thermostable properties as indicated by retention of 100% of residual activity at 70°C, and 50% of residual activity at 90°C for 10 min. Extracellular enzyme from Nocardiopsis sp. was purified by fractional precipitation with ammonium sulphate. After 60% saturation produced 1130 U mg−1 protein and yield was 28% with purification 2.7-fold. The enzyme produced by Nocardiopsis sp. has potential for industrial applications.