A novel bi-functional cold-adaptive chitinase from Chitinilyticum aquatile CSC-1 for efficient synthesis of N-acetyl-D-glucosaminidase

In order to better utilize chitinolytic enzymes to produce high-value N -acetyl-D-glucosamine (GlcNAc) from chitinous waste, there is an urgent need to explore bi-functional chitinases with exceptional properties of temperature, pH and metal tolerance. In this study, we cloned and characterized a novel bi-functional cold-adaptive chitinase called Ca Chi18A from a newly isolated strain, Chitinilyticum aquatile CSC-1, in Bama longevity village of Guangxi Province, China. The activity of Ca Chi18A at 50 °C was 4.07 U/mg. However, it exhibited significant catalytic activity even at 5 °C. Its truncated variant Ca Chi18A_ΔChBDs, containing only catalytic domain, demonstrated significant activity levels, exceeding 40 %, over a temperature range of 5–60 °C and a pH range of 3 to 10. It was noteworthy that it displayed tolerance towards most metal ions at a final concentration of 0.1 mM, including Fe 3+ and Cu 2+ ions, retaining 122.52 ± 0.17 % and 116.42 ± 1.52 % activity, respectively. Additionally, it exhibited favorable tolerance towards organic solvents with the exception of formic acid. Interestedly, Ca Chi18A and Ca Chi18A_ΔChBDs had a low K m value towards colloidal chitin (CC), 0.94 mg mL −1 and 2.13 mg mL −1 , respectively. Both enzymes exhibited chitobiosidase and N -acetyl-D-glucosaminidase activities, producing GlcNAc as the primary product when hydrolyzing CC. The high activities across a broader temperature and pH range, strong environmental adaptability, and hydrolytic properties of Ca Chi18A_ΔChBDs suggested that it could be a promising candidate for GlcNAc production.