Photosynthetic Polymer Dots–Bacteria Biohybrid System Based on Transmembrane Electron Transport for Fixing CO₂ into Poly-3-hydroxybutyrate

Abstract

Organic semiconductor-microbial photosynthetic biohybrid systems show great potential in light-driven biosynthesis. In such a system, an organic semiconductor is used to harvest solar energy and generate electrons, which can be further transported to microorganisms with a wide range of metabolic pathways for final biosynthesis. However, the lack of direct electron transport proteins in existing microorganisms hinders the hybrid system of photosynthesis. In this work, we have designed a photosynthetic biohybrid system based on transmembrane electron transport that can effectively deliver the electrons from organic semiconductor across the cell wall to the microbe. Biocompatible organic semiconductor polymer dots (Pdots) are used as photosensitizers to construct a ternary synergistic biochemical factory in collaboration with <i>Ralstonia eutropha</i> <i>H16</i> (<i>RH16</i>) and electron shuttle neutral red (NR). Photogenerated electrons from Pdots promote the proportion of nicotinamide adenine dinucleotide phosphate (NADPH) through NR, driving the Calvin cycle of <i>RH16</i> to convert CO₂ into poly-3-hydroxybutyrate (PHB), with a yield of 21.3 ± 3.78 mg/L, almost 3 times higher than that of original <i>RH16</i>. This work provides a concept of an integrated photoactive biological factory based on organic semiconductor polymer dots/bacteria for valuable chemical production only using solar energy as the energy input.