Recombinant expression of Bacillus licheniformis chitinase in B. subtilis and preparation of amino-oligosaccharides

In this study, a chitinase blchiA from Bacillus licheniformis was recombinantly expressed in B. subtilis, and the B. subtilis engineering strain (B. subtilis WS9/pHY300PLK-blchiA) was constructed. The enzyme activity in the fermentation supernatant was 0.73 U·mL⁻¹. The enzymatic properties of recombinant enzyme BLCHIA were characterized, and its best activity was obtained at pH 6.0 and 60 ℃, and the specific activity was 3.68 U·mg⁻¹. 10 mmol·L⁻¹ Cu²⁺ and Fe²⁺ could promote its activity, and its stability was good at pH 5.0−8.0 and 50−60 ℃. In addition, the catalytic ability of the recombinant enzyme on chitosan with a degree of deacetylation> 95% was significantly better than that of colloidal chitin, and the types of hydrocolloid chitin and chitosan were significantly different. Using colloidal chitin as substrate, the recombinant enzyme could mainly produce chitobiose, but using chitosan as substrate, it could produce chitosan oligosaccharide with polymerization degree of 2−7. The results have a good application prospect for viscosity reduction of chitosan and preparation of oligosaccharides with different polymerization degrees.