Efficient immobilization of lactate dehydrogenase in biocomposites of double-walled carbon nanotube-doped alginate gel

An efficient carrier, double-walled carbon nanotube-doped alginate gel (DWCNT-ALG), was researched for lactate dehydrogenase (LDH, EC 1.1.1.27) immobilization in this study. LDH was pre-adsorbed on DWCNTs and then they were encapsulated in the ALG matrices followed by Ca2+ cross-linking to form LDH-DWCNT-ALG biocomposites. Scanning and transmission electron microscope images were used to characterize the LDH-DWCNT-ALG biocomposites and the DWCNTs before and after being adsorbed by LDH. LDH leakage from LDH-DWCNT-ALG biocomposites was remarkably reduced about 61.7% compared with LDH-ALG biocomposites. The results of the optimum pH and temperature of the reaction catalyzed by immobilized LDH showed that higher activity was obtained by using LDH-DWCNT-ALG biocomposites. Operational and storage stabilities of immobilized LDH had been greatly improved after being immobilized in LDH-DWCNT-ALG hybrid biocomposites. This work showed both the biocompatibility of the organic component and the higher surface energy of nanotubes in enzyme immobilization.