Co-immobilization of β-agarase and α-agarase for degradation of agarose to prepare bioactive 3,6-anhydro-L-galactose

Agarose from biomass can be used to synthesize the rare sugar 3,6-anhydro- L -galactose ( L -AHG), and the new synthesis route and functional properties of L -AHG have always been the focus of research. Here we developed a novel method to co-immobilize Aga50D and Bp GH117 onto streptavidin-coated magnetic nanoparticles and achieved the conversion of agarose to bioactive L -AHG in one pot. Results showed that enzymes were successfully immobilized on the carrier. The activity of co-immobilized enzymes was 2.5-fold higher than that of single immobilized enzymes. Compared with free enzymes, co-immobilized enzymes exhibited enhanced thermal stability. The co-immobilized enzymes retained 79.45 % relative activity at 40 °C for 3 h, while the free enzymes only possessed 21.40 % residual activity. After eight cycles, the co-immobilized enzymes still retained 73.47 % of the initial activity. After silica gel chromatography, the purity of L -AHG obtained by co-immobilized enzymes hydrolysis reached 83.02 %. Furthermore, bioactivity experiments demonstrated that L -AHG displayed better antioxidant and antibacterial effects than neoagarobiose. L -AHG had broad-spectrum antibacterial activity, while neoagarobiose and D -galactose did not show an obvious antibacterial effect. This study provides a feasible method for the production of L -AHG by a co-immobilized multi-enzyme system and confirms that L -AHG plays a key role in the bioactivity of neoagarobiose.