A temperature-induced chitosanase bacterial cell-surface display system for the efficient production of chitooligosaccharides

Objective To establish a temperature-induced chitosanase bacterial cell-surface display system to produce chitooligosaccharides (COSs) efficiently for industrial applications. Results Temperature-inducible chitosanase CSN46A bacterial surface display systems containing one or two copies of ice nucleation protein (InaQ-N) as anchoring motifs were successfully constructed on the basis of Escherichia coli and named as InaQ-N-CSN46A (1 copy) and 2InaQ-N-CSN46A (2 copies). The specific enzyme activity of 2InaQ-N-CSN46A reached 761.34 ± 0.78 U/g cell dry weight, which was 45.6% higher than that of InaQ-N-CSN46A. However, few proteins were detected in the 2InaQ-N-CSN46A hydrolysis system. Therefore, 2InaQ-N-CSN46A had higher hydrolysis efficiency and stability than InaQ-N-CSN46A. Gel permeation chromatography revealed that under the optimum enzymatic hydrolysis temperature, the final products were mainly chitobiose and chitotriose. Chitopentaose accumulated (77.62%) when the hydrolysis temperature reached 60 °C. FTIR and NMR analysis demonstrated that the structures of the two hydrolysis products were consistent with those of COSs. Conclusions In this study, chitosanase was expressed on the surfaces of E. coli by increasing the induction temperature, and chitosan was hydrolysed directly without enzyme purification steps. This study provides a novel strategy for industrial COS production.