Synthesis of a Lignin-Enhanced Graphene Aerogel for Lipase Immobilization

A novel lignin-enhanced graphene aerogel (LGA) was prepared by one-step hydrothermal synthesis, and lipase from Pseudomonas sp. (PSL) was immobilized on LGA successfully by interfacial activation. The catalytic activity and enantioselectivity of LGA-PSL for the preparation of (S)-2-octanol by an enantioselective transesterification were improved obviously. The characterization of LGA and LGA-PSL was performed. X-ray diffraction and Fourier transform infrared spectroscopy demonstrated the formation of numerous electrostatic and hydrogen bonds between lignin and graphene in the aerogel structure. In addition, the specific surface area pore size analyzer (BET) test proved that the introduction of lignin significantly increased the specific surface area and pore size of the aerogel material, which improved the immobilization efficiency of lipase in the aerogel. The introduction of lignin has changed the original lamellar structure of the graphene oxide (GO) aerogels. The lignin cross-linked with the GO lamellae through hydrogen bonding, causing a porous structure to form between the original lamellae, thus increasing their specific surface area. The immobilized lipase (LGA-PSL) was used for the preparation of (S)-2-octanol by an enantioselective transesterification, and the reaction conditions for this enzymatic transesterification had been optimized. LGA-PSL exhibited a high catalytic performance and could be reused four times in this reaction. Based on these results, LGA as an immobilization carrier had potential applications in the industrial application of lipase.