Production of lactobionic acid using an immobilized cellobiose dehydrogenase/laccase system on magnetic chitosan spheres

Abstract

Lactobionic acid (LBA) has numerous promising applications in food, pharmaceutical, cosmetics and chemical fields. LBA can be produced by cellobiose dehydrogenase (CDH)/laccase (Lac) bi‐enzymatic system with redox mediator, in which CDH catalyzes the oxidation of lactose into LBA, while LAC serves as a regenerative enzyme to simultaneously regenerate the redox mediator as electron acceptor for CDH. Despite this CDH/LAC system is effective in catalyzing the oxidation of lactose into LBA, easy deactivation of free enzymes throughout the biocatalysis process limited its industrial implementation. In this study, a new cellobiose dehydrogenase from Aspergillus fumigatus (AfCDH) was characterized. AfCDH and LAC were separately immobilized on the glutaraldehyde-modified magnetic chitosan spheres (MCS) with the activity yields of immobilization 61.54 % and 14.1 %, respectively. Immobilized AfCDH displayed better thermal stability and retained 60 % of initial activity after incubation at 50 °C for 4 h, in contrast, the residual activity of free AfCDH was hardly detected under the same condition. Our study demonstrated that the immobilized AfCDH/LAC system was efficient for bioproduction of LBA. 100 g/L of lactose was completely converted to LBA with a space-time yield of 7.14 g/L h This immobilized AfCDH/LAC system had good reusability and retained 70 % activity after 10 cycles of reuse.