A novel beta-propeller phytase from Pedobacter nyackensis MJ11 CGMCC 2503 with potential as an aquatic feed additive.

A phytase with high activity at neutral pH and typical water temperatures ( approximately 25 degrees C) could effectively hydrolyze phytate in aquaculture. In this study, a phytase-producing strain, Pedobacter nyackensis MJ11 CGMCC 2503, was isolated from glacier soil, and the relevant gene, PhyP, was cloned using degenerate PCR and thermal asymmetric interlaced PCR. To our knowledge, this is the first report of detection of phytase activity and cloning of phytase gene from Pedobacter. PhyP belongs to beta-propeller phytase family and shares very low identity ( approximately 28.5%) with Bacillus subtilis phytase. The purified recombinant enzyme (r-PhyP) from Escherichia coli displayed high specific activity for sodium phytate of 24.4 U mg(-1). The optimum pH was 7.0, and the optimum temperature was 45 degrees C. The K (m), V (max), and k (cat) values were 1.28 mM, 71.9 micromol min(-1) mg(-1), and 45.1 s(-1), respectively. Compared with Bacillus phytases, r-PhyP had higher relative activity at 25 degrees C (r-PhyP (>50%), B. subtilis phytase (<8%)) and hydrolyzed phytate from soybean with greater efficacy at neutral pH. These characteristics suggest that r-PhyP might be a good candidate for an aquatic feed additive in the aquaculture industry.