(217bo) Highly Reactive Non-Woven Photoreactive Cellular Biocomposites for Gas-Phase CO2 Recycling and H2 Production

Synthetic biology has the potential to engineer photoreactive microbes to have significant stability advantages over isolated enzymes and synthetic harvesting materials that harvest sunlight, absorb CO₂ and produce fuels. What is needed are inexpensive methods to concentrate and stabilize photoreactive cells into composite sheet-like materials that can be easily illuminated, function in the gas-phase much like natural leaves without dehydration, and can be stored dry without loss of reactivity.  We report the microstructure and reactivity of two novel nonwoven cellulose fiber (paper) cellular biocomposites for long-term stabilization of concentrated  photosynthetic microorganisms. Cells can either be deposited as a thin nanoporous water-borne latex coating or incorporated during the paper making process as an integral highly porous biocomposite (microbial paper). The paper pores function as a transport network to keep cells hydrated with nutrients, eliminate waste materials and separate secreted products. CO₂ absorption without cell outgrowth has been monitored for >500 hours from cellular photocomposites of  five strains of cyanobacteria (Synechococcus PCC7002, Synechocystis PCC6308, Synechocystis PCC6803, Cyanothece ATCC51142 and Anabaena PCC7120) coated along with non-toxic latex binder emulsions on chromatography paper. Hydrogen gas production from acetate by the activity of the nitrogenase in CGA009 Rps. palustris entrapped at very high concentration in microbial paper can be sustained for >1000 hours at a rate of 4.00 ± 0.28 mmol H₂ m² h^-1 following rehydration. SEM images of rehydrated composite microstructure reveal the distribution of concentrated cells on and between paper fibers that do not clog the pore space, which allows for perfusive flow through the cellulose fiber matrix. Current efforts are focused on the characterization of the latex binder wet coalescence process on paper, intensification of reactivity, and optimization of the coating/biocomposite formulation for improved mechanical stability and reactivity. Understanding  the cell-fiber interactions will enable intensification and stabilization of other types of photoreactive cells on non-woven supports. The composite microbial paper concept has been demonstrated. These composite non-woven paper-based materials can be engineered in the future as cost-effective biophotocatalysts that combine intensification, uniform illumination, stabilization of reactivity and separation capabilities for applications in biosolar energy.