CLONING OF THE THERMOSTABLE PHYTASE GENE (PHY) FROM BACILLUS SP. DS11AND ITS OVEREXPRESSION IN ESCHERICHIA-COLI

Phytase hydrolyzes phytate to release inorganic phosphate, which would decrease the addition of phosphorus to feedstuffs for monogastric ani mals and thus reduce environmental pollution. The gene encoding phytas e from Bacillus sp. DS11 was cloned in Escherichia coli and its sequen ce determined. A 560-bp DNA fragment was used as a probe to screen the genomic library. It was obtained through PCR of Bacillus sp. DS11 chr omosomal DNA and two oligonucleotide primers based on N-terminal amino acid sequences of the purified protein and the cyanogen bromide-cleav ed 21-kDa fragment. The phy cloned was encoded by a 2.2-kb fragment. T his gene comprises 1152 nucleotides and encodes a polypeptide of 353 a mino acids with a deduced molecular mass of 41 808 Da. Phytase was pro duced to 20% content of total soluble proteins in E. coli BL21 (DE3) u sing the pET22b(+) vector with the inducible T7 promoter. This is the first nucleic sequence report on phytase from a bacterial strain. (C) 1998 Federation of European Microbiological Societies. Published by El sevier Science B.V.