A thermophilic chitinase 1602 from the marine bacteriumMicrobulbifersp. BN3 and its high-level expression inPichia pastoris

Chitinases play an important role in many industrial processes, including the preparation of oligosaccharides with potential applications. In the present study, a 1,713 bp gene ofChi1602, derived from a marine bacteriumMicrobulbifersp. BN3, encoding a GH18 family chitinase, was expressed at high levels inPichia pastoris. Distinct from most of the marine chitinases, the recombinant chitinase 1602 exhibited maximal activity at 60 degrees C and over a broad pH range between 5.0 and 9.0, and was stable at 50 degrees C and over the pH range 4.0-9.0. The hydrolytic products derived from colloidal chitins comprised mainly (GlcNAc)(2)and GlcNAc, indicating that rChi1602 is a GH18 processive chitinase in conformity with its hypothetical structure. However, rChi1602 showed traces of beta-N-acetylglucosaminidase activity on substrates such as powder chitin, chitosan, and ethylene glycol chitin. The thermophilic rChi1602, which manifests adaptation to a wide pH range and can be expressed at a high level inP. pastoris, is advantageous for applications in industrial processes.