Combining Liposomal Photocatalysts with Whole-Cell Catalysts for One-pot Photobiocatalysis

Cooperative photobiocatalytic processes have seen extensive potentials for the synthesis of both bulk and fine chemicals owing to their versatility, eco-friendliness, and cost-effectiveness. Nevertheless, developing a universal and effective synthetic strategy compatible with both catalytic systems remains challenging. In this study, we explored cationic liposomes as biocompatible photocatalyst encapsulation systems and combined them with bacteria overexpressing enzymes for two-step and three-step cascade reactions. Specifically, the water-soluble photocatalyst anthraquinone-2-sulfonate (AQS), which can oxidize benzyl alcohol, is encapsulated within the core of cationic liposomes composed of dioleoyl-3-trimethylammonium propane (DOTAP) and the helper lipid cholesterol. The positive charge on the liposome surface enabled electrostatic interactions with the negative charges on the membrane of Escherichia coli cells. Bacterial cells overexpressing various enzymes, such as Candida antarctica lipase B (CalB) and benzaldehyde lyase (BAL), and coated with liposomes enabled the production of added value compounds through cascade reactions with excellent production. These cascades involve CalB-catalyzed hydrolysis, BAL-catalyzed condensation, and AQS-driven photo-oxidation reactions. Therefore, the strategy offers more possibilities of combining photocatalysis with biocatalysis for recoverability, enhanced mass transfer, and enhanced compatibility in both industrial biotechnology and synthetic chemistry.