Purification and characterization of a novel chitinase gene from Paecilomyces thermophila expressed in Escherichia coli

A novel chitinase gene (PtChiA) from the thermophilic fungus Paecilomyces thermophila was cloned and expressed in Escherichia coli as an intracellular soluble protein. The gene sequence alignment indicates that PtChiA belongs to glycoside hydrolase (GH) family 18 and has an open reading frame comprising of 1473 bp nucleotide sequences with five introns. PtChiA encodes 400 amino acids without any predicted signal peptide. PtChiA was purified by Ni-IDA chromatography. It displayed an acidic optimum pH of 4.5 and broad pH stability (pH 4.0–10.5). The enzyme exhibited an optimal temperature of 50 °C and was stable up to 40 °C. PtChiA was strongly inhibited by anionic detergent SDS, and also by metal ions Hg2+ and Mn2+. It did not exhibit any antifungal activity against pathogenic fungi. It has the ability to hydrolyze colloidal chitin into chito-oligomers suggesting its use in conversion of chitin waste into chito-oligosaccharides.