Production of Thermostable a-amylase by Bacillus cereus MK in solid state fermentation: Partial purification and characterization of the enzyme

Abstract

Thermostable a-amylase production under solid state fermentation was investigated using isolated thermophilic Bacillus cereus MK. Optimization of process parameters followed by leaching parameters for enhanced enzyme yields were carried out. The optimum temperature, pH, incubation period, inoculation size and substrate to moisture ratio were found to be 55 C, 7.0, 24 h, 15 % (v/w) and 12.5 (w/v), respectively. Among different carbon, nitrogen and trace elements supplemented, glucose, peptone and calcium chloride, respectively enhanced enzyme production. The optimum leaching parameters such as solvents, solvent volume, physical state, solvent temperature and solvent pH for effective extraction of amylase from the fermented bran were found to be sodium acetate buffer (0.1M, pH 5.6), 1:2.5 (w/v), agitation, 50 C and 7.0, respectively. An overall 14 fold increase in enzyme production was attained by optimization of process conditions and leaching parameters in SSF. The crude amylase showed maximum activity at pH 7.0 and 90 C. The enzyme was stable at 90 C for 1h. However in the presence of 4% (w/v) starch, the stability of enzyme was increased to100 C up to 2h.