Production of ChiA-Pt70, a new organic solvent-tolerant extracellular chitinase from Paenibacillus timonensis strain LK-DZ15

A new extracellular chitinase (ChiA-Pt70) was produced and purified from a newly isolated Paenibacillus timonensis strain LK-DZ15. The maximum chitinase activity recorded after 44-h of incubation at 30°C was 11,500 U/mL. Pure enzyme was obtained after ammonium sulphate precipitation (40-70%) followed by sequential column chromatographies on fast performance liquid chromatography (FPLC) and high performance liquid chromatography (HPLC). Based on matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis, the purified enzyme is a monomer with a molecular mass of 70,166.11 kDa. The sequence of the 25 NH₂-terminal residues of the mature ChiA-70 showed high homology with Paenibacillus GH-18 chitinases family. Optimal activity was achieved at pH 4.5 and 80°C. The pure enzyme was completely inhibited by p-chloromercuribenzoic acid (p-CMB) and N-ethylmaleimide (NEM). Chitinase activity was high on colloidal chitin, chitin azure, glycol chitin, glycol chitosane, chitotriose, and chito-oligosaccharide while it did not hydrolyse chitibiose and amylose. Furthermore, thin-layer chromatography (TLC) analysis from enzymatic catalyzed hydrolysis of chitin-oligosaccharides showed that ChiA-Pt70 acted as an endo-splitting enzyme. Its K_m and k_cat values were 0.611 mg colloidal chitin/mL and 87,800 s^-1, respectively. Interestingly, its catalytic efficiency was higher than those of chitinases ChiA-Mt45 from Melghiribacillus thermohalophilus strain Nari2A^T, ChiA-Hh59 from Hydrogenophilus hirchii strain KB-DZ44, Chitodextrinase^® from Streptomyces griseus, and N-acetyl-β-glucosaminidase^® from Trichoderma viride. Therefore, ChiA-Pt70 exhibited remarkable biochemical properties suggesting that it is suitable for the enzymatic degradation of chitin.