Chitosan derivative functionalized carbon nanotubes as carriers for enzyme immobilization to improve synthetic efficiency of ethyl caproate

Abstract To acquire stable non-covalent functionalized carbon nanotubes with good dispersion and biocompatibility, cinnamaldehyde-chitosan conjugates (CA-CS conjugates) were synthesized to modify carbon nanotubes. The functionalized carbon nanotubes (CA–CS–CNTs) were characterized by FTIR, TGA and TEM. CA–CS–CNTs could be dispersed well in water, and the loading of CA-CS conjugates on carbon nanotubes was about 23%. CA–CS–CNTs were further extended to immobilize porcine pancreatic lipase (PPL), and the successful attachment of PPL onto CA–CS–CNTs was revealed by the result of FTIR. The lipase loading and relative lipase hydrolysis activity of immobilized PPL (CA–CS–CNTs-PPL) reached 248 mg/g and 8064 U/g, respectively. CA–CS–CNTs-PPL possessed good thermostability, and maintained 69% of enzyme activity after reusing 7 times. Additionally, characteristic flavor of strong aromatic liquors, ethyl caproate, was prepared using CA–CS–CNTs-PPL as biocatalysts, and the highest yield of 88% was observed. CA–CS–CNTs-PPL possessed positive properties, which could be expected to become low-cost and useful biocatalysts.