Abstract
In order to improve the activity and stability of phytase fromBacillus amyloliquefaciens, site-directed mutagenesis has been performed base on the previous recombinantE.coliBL21 harboring the expression vector ofphyC. Mutation residues were chosen based on the sequence alignments and structure analysis of neutral phytsaes from different microorganisms. Site-directed mutagenesis techniques were used to get three mutants (D148E/H149R, Q67E/N68R, and D191E), then the mutants were expressed and purified. Enzymatic characters of different mutants were investigated. The results indicated that the optimum pH of all mutants were 7.0, and the optimum temperature were between 65 °C–70 °C. The maximum specific activity of mutant D148E/H149E was 27.84 U/mg which was 2.19 times than that of the wild-type phytase. The half inactivation temperature of D191E was 4.5 °C higher than that of the wild-type phytase. Fluorescence emission spectra showed that slight differences were among the structures of the mutant phytases. The phytases described here which have increased activity and thermostability may have promosing potential as feed additives in animal diets.
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