Improved thermostability and enzyme activity of a recombinant phyA mutant phytase from Aspergillus niger N25 by directed evolution and site-directed mutagenesis.

•Three recombinant phyA mutant strains (PP-NPm-8, PP-NPep-6A and I44E/T252R-PhyA) were constructed.•Improving catalytic efficiency or thermostability of Aspergillus niger N25 phytase, by error-prone PCR or site-directed mutagenesis.•Directed evolution and site-directed mutagenesis were further applied to improve the modified phytase properties.•These mutations could produce cumulative or synergistic improvements in thermostability or catalytic efficiency of phytase.•It can do some for industrial production work.