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

Appl Microbiol Biotechnol (2009) 83:249259 DOI 10.1007/s00253-008-1835-1

BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS

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

Huoqing Huang & Na Shao & Yaru Wang & Huiying Luo &

Peilong Yang & Zhigang Zhou & Zhichun Zhan & Bin Yao

Received: 5 November 2008 /Revised: 14 December 2008 /Accepted: 17 December 2008 /Published online: 13 January 2009 # Springer-Verlag 2009

Abstract A phytase with high activity at neutral pH and typical water temperatures (25C) could effectively hydro-lyze 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 (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 mg1. The optimum pH was 7.0, and the optimum temperature was 45C. The Km, Vmax, and kcat values were 1.28 mM, 71.9 mol min1 mg1, and 45.1 s1, respectively. Compared with Bacillus phytases, r-PhyP had higher relative activity at 25C (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.

Keywords Aquaculture . Phytate . Beta-propeller phytase . Pedobacter nyackensis . Bacillus phytases

Introduction

Most of the phosphorus in plants occurs as a nonbioavailable organic complex termed phytate (Reddy et al. 1982) that also forms insoluble complexes with nutritionally important metals and proteins, thereby decreasing their bioavailability as well (Wodzinski and Ullah 1996). Phytase is an enzyme that initiates the stepwise hydrolysis of phosphomonoesters and liberates inorganic phosphate from phytate (Mullaney and Ullah 2003). Numerous experiments have shown that adding phytase to animal feed replaces partial inorganic phosphorus supplementation, improves the bioavailability of minerals, and reduces total phosphorus excretion by about 50% (Kemme et al. 1997; Liu et al. 1997; Yi et al. 1996). For these reasons, it has been used worldwide as...