S144: Progress towards designing photobiological fuel cells: thin biocomposite paper coatings of live cells and latex particles deposited by continuous convective assembly

We have introduced continuous convective assembly as a rapid and reproducible method for fabricating biocomposite coatings containing hydrogen-producing or oxygen-evolving cells.  Photobiological hydrogen production by the purple nonsulfur bacterium Rhodopseudomonas palustris, combined with oxygen evolution by the green algae Chlamydomonas reinhardtii, is of interest because it holds the promise of generating photoreactive fuel cells from abundant inexpensive resources – sunlight and non-carbohydrate waste organics.  Convective assembly offers controlled deposition of particle or cell coatings with tailored composition, particle packing, and monolayer thicknesses.  Thin nanoporous coatings of monolayers of photoreactive cells surrounded by high T_g, latex polymer particles (for improving coating adhesion) have several advantages  including enhanced cell stability, increased reactivity, minimized diffusion resistance to nutrients, reduced light scattering and low cost. We demonstrate that thin adhesive coatings can be fabricated using a continuous meniscus deposition process on paper  that can be dried and rehydrated without loss of reactivity.  Preliminary results show stable photohydrogen production from acetate by  latex coatings of nitrogen-limited Rsp. palustris CGA009 or sulfur-limited C. reinhardtii CC-124 incubated under anoxygenic conditions (argon atmosphere).  The immobilized cell coatings maintained photosynthetic reactivity over the entire incubation period, producing hydrogen (without nutrient addition).  We aim to correlate light absorption and scattering data to coating microstructure and reactivity, as a means of optimizing light absorption and gas production efficiency in multi-layer flexible biocomposite devices.