Characterization of a thermostable, CaCl2-activated and raw-starch hydrolyzing alpha-amylase from Bacillus licheniformis AT70: Production under solid state fermentation by utilizing agricultural wastes

• The production of AT70 alpha-amylase was optimized about 10 folds using starch (0.1%) and ammonium chloride (2.0%).
• This is the first report for the production of bacterial alpha-amylase by using date waste in SSF.
• The very salient improvement (2.5 folds) of the enzyme thermo-stability was observed after addition of Ca2+ into reaction mixture.
• AT70 alpha-amylase showed about 34% activity toward commercial solid detergents Shooma.
• AT70 alpha-amylase exhibited remarkable hydrolytic activity in 14–20% (w/v) of raw corn starch at 55 °C.

B. licheniformis AT70 which produced a thermophilic, raw-starch degrading alpha-amylase was isolated from Gorooh hot springs in Kerman province. Maximum production of AT70 alpha-amylase was obtained in the presence of starch (as a carbon source) and ammonium chloride (as a nitrogen source) with 388 and 329 U/ml enzyme yield, respectively. SSF was also carried out using various agricultural and kitchen wastes and results showed that the maximum yield of AT70 alpha-amylase production was obtained by date waste and wheat bran, respectively (10%, w/v). The thermal stability of the AT70 alpha-amylase was increased about 2.5 folds at 60 °C. AT70 alpha-amylase showed the maximum activity at 1.5 M NaCl by 42% and local detergent Shooma enhanced the alpha-amylase activity about 34%, compared to control. Furthermore, AT70 alpha-amylase exhibited remarkable hydrolytic activity in a range of 14–20% (w/v) of raw corn starch at 55 °C. These results indicated that AT70 alpha-amylase has great potential applications for the raw-starch degrading.

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