A thermophilic chitinase 1602 from the marine bacterium Microbulbifer sp. BN3 and its high-level expression in Pichia pastoris.

Abstract

Chitinases play an important role in many industrial processes, including the preparation of oligosaccharides with potential applications. In the present study, a 1,713bp gene of Chi1602, derived from a marine bacterium Microbulbifer sp. BN3, encoding a GH18 family chitinase, was expressed at high levels in Pichia pastoris. Distinct from most of the marine chitinases, the recombinant chitinase 1602 exhibited maximal activity at 60°C and over a broad pH range between 5.0 and 9.0, and was stable at 50°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 β-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 in P. pastoris, is advantageous for applications in industrial processes.