UV mutagenesis for the overproduction of thermoalkali-stable α-amylase from Bacillus subtilis TLO3 by fermentation of stale bread: Potential application as detergent additive

The aims of this study were (1) to test different starch-rich wastes and different chemical pretreatments for α-amylase production by the strain Bacillus subtilis TLO3; (2) to investigate the possibility of using UV mutagenesis to improve the production and characteristics of α-amylase and (3) to investigate the possibility of its applications as additive to detergents. The results indicated that stale bread was the best substrate for α-amylase production (107.3 U/min ±0.001). A mutant strain was isolated by random mutagenesis using UV-irradiations with an overproduction of α-amylase up to 473.3 U/min ±0.03 against 100 U/min ±0.06 with the parental strain. The alkali pretreatment enhanced the production of α-amylase by the mutant (1526.31 U/min ±0.67), compared to the untreated substrate (473.3 U/min ±0.03). The precipitated α-amylase was thermostable and alkalistable with an optimum activity at 70 °C and pH 8, and showed high stability with laundry detergents. The wash performance tests indicated that the precipitated α-amylase was effective in cleaning different stains (tomato sauce, chocolate sauce, coffee and tea).