A novel thermostable phytase from the fungus Aspergillus aculeatus RCEF 4894: gene cloning and expression in Pichia pastoris

摘要

A novel gene of thermostable phytase, phyA, was isolated by polymerase chain reaction (PCR) techniques from Aspergillus aculeatus RCEF 4894. The full-length phyA gene comprises 1,404bp and encodes 467 amino-acid residues, including a 19-residue putative N-terminal signal peptide. The phytase of A. aculeatus was a novel addition to the histidine-acid phosphatase family, as evidenced by both the conserved motifs RHGXRXP and HD in the amino-acid sequence, and 3D structure models. The recombinant phytase was overexpressed in Pichia pastoris, and its specific activity reached 3,000UmL super(-1) at the optimum pH of 5.5. This recombinant, thermostable phytase was able to withstand temperatures of up to 90 degree C for 10min, with a loss of only 13.9% of initial enzymatic activity, and showed high activity with phytic-acid sodium salt at a pH range of 2.5-6.5. The broad pH optima and high thermostability of the phytase makes it a promising candidate for feed-pelleting applications.