Design and characterization of a chimeric alginate lyase for immobilization to produce well-defined oligosaccharides

Recently, a novel two-domain alginate lyase (AlyAL01) was cloned from Algibacter sp. and successfully overexpressed in Escherichia coli BL21(DE3). Biochemical analysis showed that the N-terminal carbohydrate-binding module (CBM) of AlyAL01 had no effect on the enzyme activity and product distributions. Therefore, the N-terminal CBM was substituted with CBM3 to confer the designed chimeric protein with the ability to specifically bind to regenerated amorphous cellulose. As anticipated, the designed chimeric protein (CBM3-L1) exhibited a similar enzyme activity. Moreover, it was found that the CBM3-L1 combined the purification and immobilization in one step with high immobilized efficiency of 65.8%. The immobilized enzyme exhibited good storage stability and moderate reusability. The immobilized enzyme could keep 85% activity when incubated at 4°C for 60 days and 70% activity when incubated at 25°C for 30 days. Furthermore, the immobilized CBM3-L1 kept about 50% of its initial activity after being reused five times. Finally, immobilized CBM3-L1 successively produced well-defined alginate oligosaccharides (AOS) with DPs of 2–6 by controlling reaction time. In sum, our current study provided a feasible strategy for well-defined AOS production.