Photoenzymatic decarboxylation to produce renewable hydrocarbon fuels: A comparison between whole-cell and broken-cell biocatalysts

Abstract

The recently discovered fatty acid photodecarboxylase from Chlorella variabilis NC64A (CvFAP) is a potential photoenzyme to produce sustainable aviation fuels from lipid-rich wastewater. Herein, we compared the catalytic performance in photoenzymatic decarboxylation reactions between recombinant Escherichia coli cells containing CvFAP (CvFAP@E. coli) and broken cells (CvFAP BCs) prepared by supersonic treatment of CvFAP@E. coli under various catalytic conditions for the first time. The conversion of palmitic acid as a model substrate by CvFAP BCs was 1.87 times higher than that by CvFAP@E. coli at a rotation speed of 100 rpm due to the absence of mass transfer resistance from the cytomembrane for CvFAP BCs. However, no significant difference in the conversion of palmitic acid between CvFAP@E. coli (88.4%) and CvFAP BCs (95.4%) was obtained under the optimal reaction conditions: a cell dry weight of 35.2 mg·mL−1, a rotation speed of 200 rpm, a pH of 8.0, and a light intensity of 200 μmol·m−2·s−1 for 3 h. Good stabilities for CvFAP BCs (92.4%) and CvFAP@E. coli (87.7%) were retained at 30 °C for 3 days. CvFAP BCs was capable of decarboxylating palmitic acid at a high concentration of 54 mM with the highest conversion rate of 17.2 mM/h as previously reported. This work demonstrates the continuous potential of CvFAP in producing hydrocarbon fuels.