Cloning, characterization and substrate degradation mode of a novel chitinase from Streptomyces albolongus ATCC 27414

Cloning, expression and characterization of a novel chitosanase from Streptomyces albolongus ATCC 27414

A gene encoding chitosanase from Streptomyces albolongus was cloned, sequenced and expressed in Escherichia coli. The novel recombinant enzyme (Csn21c) was purified by Ni-NTA Superflow Column and showed a molecular mass of 29.6 kDa by SDS-PAGE. The enzyme Csn21c showed the optimal activity in 50 mmol/L Tris-HCl buffer, pH 8.0, and 50 °C and it was strongly activated (2-fold) by Mn²⁺. It belonged to glycoside hydrolase 46 family according to NCBI database (http://www.ncbi.nlm.nih.gov/) and displayed an exo-type cleavage pattern, hydrolyzing chitosan mainly into d-glucosamine (GlcN) and chitobiose ((GlcN)₂) as confirmed by TLC and MS analysis. This study demonstrated that Csn21c can be an effective tool to produce abundant glucosamine and chitooligosaccharides (COS) from chitosan.

Efficient enzymatic hydrolysis of ionic liquid pretreated chitin and its dissolution mechanism

Colloidal chitin, the substrate of chitinase with an open hydrated gel-like structure, can be obtained by treatment using either traditional hydrochloric acid (HCl) or ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). IL-pretreated chitin provided an efficient production of N-acetylglucosamine (175.62 mg g chitin) and N,N'-diacetylchitobiose (341.70 mg g chitin) with a conversion of 61.49% at 48 h catalyzed by chitinase from Streptomyces albolongus ATCC 27414. A short time second homogenization treatment after IL pretreatment can increase the conversion to 76.11%. A comprehensive characterization and comparison of chitin with different pretreatments suggested that enzymatic performances were correlated with the structural changes (size of the grains and porosity), high decrease in crystallinity, and high enzyme adsorption. The NMR spectroscopy studies of N-acetylglucosamine solvation in [Emim][OAc] clearly suggest that hydrogen bonding is formed between the hydroxyls of N-acetylglucosamine and both the anions and cations of the IL.