Carbon–ceramic composites for enzyme immobilization

Abstract

Tunable carbon nanofiber-coated monoliths as carriers for enzyme adsorption are presented. Carbon-nanofibers (CNFs) were grown on monoliths with different microstructure. ‘‘Classical’’ cordierite monoliths were compared to novel acicular mullite (ACM) monoliths, with a more open wall structure. This open structure allows for a higher CNF-loading without affecting the open structure of the monoliths. The composites were used as a carrier for lactase from Aspergillus oryzae. ACM monoliths allow for a higher CNF loading, and thus for a higher enzyme loading. Lactase adsorption per gram of carbon increases by 15–20% compared to cordierite samples. The total enzyme adsorption capacity for CNF-coated ACM and cordierite monoliths was found to be 350 and 300 mg g-1Carbon respectively. Oxidation treatment of the CNFs affected the surface chemistry, while the porosity was not affected. The growth catalyst could be removed completely from both the support and the CNFs by treatment in HCl or HNO3, without destroying the carbon structure.