Molecular cloning and the biochemical characterization of two novel phytases from B. subtilis 168 and B. licheniformis

Abstract

A novel phytase gene (phyL) was cloned from Bacillus licheniformis by multiple steps of degenerate and inverse PCR. The coding region of the phyL gene was 1,146 bp in size and a promoter region of approximately 300 bp was identified at the upstream sequence. This gene, together with a phytase gene (168phyA) identified in the B. subtilis strain 168 genome by a homology search, was cloned and over-expressed in B. subtilis using a φ105MU331 prophage vector system. Up to 35 units of phytase/ml were secreted into the culture media; and mature enzymes of around 44-47 kDa were purified for characterization. Both phytases exhibited broad temperature and pH optima and showed high thermostability. Of the two, the phytase encoded by phyL exhibited higher thermostability, even at a lower calcium concentration, as it was able to recover 80% of its original activity after denaturation at 95°C for 10 min. With their neutral pH optima and good temperature stabilities, these Bacillus phytases are good candidates for animal feed applications and transgenic studies.