Keratinase is one of the important proteases, which is widely used for converting keratin of the keratinaceous materials into various value-added products. In this study, a popular keratinase producer, Bacillus licheniformis PWD-1, was exposed to ultraviolet (UV) and He-Ne laser irradiations to develop high keratinase-producing mutants. Laser irradiation showed a higher lethality of cells (94%) than UV treatment (92%), whereas laser treatment required a longer time (75 min) than UV treatment (20 min). A total of 58 mutants were selected from 176 isolates to study protein and keratinase production capability of the mutants. The highest keratin-to-casein (K:C) ratio (1.43) was exhibited by LU11 mutant, which was obtained from the combined laser and UV irradiations. The purified keratinase (65 kDa) of LU11 showed 40% yield 1.7-fold purity, while the respective value for wild enzyme was 29% and 1.3-fold. Both enzymes showed optimal activity at 55 ℃ and pH 8, with a Z value of 15.78 ℃ for LU11 and 19.72 ℃ for wild strain. The Vmax and specific constant (Kcat/Km) of the mutant enzyme were 357.17 U/ml and 33.11 min-1 mM-1, respectively, which were significantly higher than the respective values of wild enzyme (102.04 U/ml and 28.36 min-1 mM-1).
Keywords: Bacillus licheniformis; Enzyme catalysis; K:C ratio; Laser-UV mutagenesis; Microbial keratinase.
© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.