Influence of the support surface properties on the protein loading and activity of lipase/mesoporous carbon biocatalysts

Three mesoporous carbons were selected as supports for two lipases from Candida antarctica (CALA and CALB). A commercially available mesoporous carbon (MB) was used as starting material. Two additional supports were prepared from MB by heat treatment at 1773 K and oxygen plasma, bringing about materials with marked differences in both textural and surface chemical properties. Heterogenisation of lipases was performed at different immobilisation pH (4–8 range). The lipase/mesoporous carbons showed an enhancement of the catalytic activity in the kinetic resolution of (±)-1-phenylethanol when compared to that of the unsupported enzymes. For CALA, enzyme loadings were controlled by enzyme–support electrostatic interactions, whereas adsorption of CALB was ruled by specific interactions related to the enzyme and support surface chemistry. No direct correlation was found between the protein loads and catalytic activity. The catalytic activity of CALA/carbon systems was found to depend on both immobilisation pH and selected support more strongly than CALB biocatalysts. Changes observed in the support textural properties affect less to protein adsorption and catalytic activity. Operational stability tests were carried out with selected biocatalysts, with no significant activity loss being observed after 10 consecutive cycles of use and recovery.

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► Results of the catalytic activity of the systems rather than only adsorption capacities are presented. We have demonstrated that there is not a direct correlation between the amount of lipase loaded on mesoporous carbons and the final activity of the biocatalysts.
► Even if only enzyme adsorption is considered, the influence of different carbon surface chemical environments on the loading capacity of the mesoporous supports is reported. As a consequence, this study has lead to quite different conclusions of those outlined in previous works. In our case, adsorption of lipases on the carbon supports are strongly controlled by the protein-carbon surface interactions, including electrostatic, hydrophobic and specific (acid–base).
► Results of the operational stability of the mesoporous carbon biocatalysts are included.