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 BpGH117 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.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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