Heterologous expression of two novel deacetylases from Bacillus altitudinis JYY-02 and their applications in the enzymatic modification of chitin and xylan

Deacetylation can convert chitin into chitosan with superior properties and improve xylan's hydrolytic efficiency, broadening their applications in biomedicine, agriculture, and bio-based materials. In this study, two novel deacetylase genes encoding polysaccharide deacetylase (PdaA) and chitin oligosaccharide deacetylase (COD), were screened from Bacillus altitudinis JYY-02 and heterologously expressed in Escherichia coli Rosetta (DE3). The recombinant deacetylases were subsequently purified using Ni–NTA affinity chromatography. Comprehensive enzymatic characterization revealed that PdaA exhibited optimal activity at pH 5.0 and 30 °C, while COD performed best at pH 6.5 and 30 °C. Both deacetylases demonstrated exceptional thermal stability, retaining over 90% of their activity after incubation at 50 °C for 1 h. Kinetic studies showed that PdaA and COD displayed efficient substrate binding capabilities, with K m of 58.58 μg/mL and 72.05 μg/mL. Functional analyses revealed the two deacetylases could effectively catalyze the deacetylation of colloidal chitin with a deacetylation degree of 59.81-69.02%. Moreover, when combined with xylanases, they significantly improved xylan hydrolysis, increasing the yield of reducing sugar by 35-40% compared to conventional acid hydrolysis methods. The superior catalytic properties and stability of these deacetylases position them as promising biocatalysts for the enzymatic modification of commercial chitin and xylan.