Synthetic biology proposes to engineer photoreactive microbes to be more stable than isolated enzymes and synthetic light harvesting materials for absorbing CO2, generating C-C bonds and secreting fuels. Dried and rehydrated cellular biocomposites containing concentrated viable cells in contact with the gas-phase will enable true continuous gas-phase biocatalysts. We report the microstructure and reactivity of model nonwoven (paper) cellular biocomposites for long-term stabilization of concentrated photosynthetic and non-photosynthetic microorganisms that remain hydrated in the gas-phase by the liquid in the paper pores. Cells can be deposited as thin nanoporous latex coatings, coated onto polyelectrolytes, or incorporated during paper manufacture to generate highly porous biocomposites (microbial paper). The paper pores function as a transport network to keep cells hydrated with nutrients, eliminate waste materials and separate secreted products. One model system, cyanobacteria extrusively coated along with non-toxic latex binder emulsions on chromatography paper, achieved CO2 uptake rates comparable to plant leaves (5.67 mmol m-2 h-1). In a second model system, H2  gas production from acetate by CGA009 Rps. palustris entrapped in microbial paper can be sustained for >1,000 hours at a rate of 4.00 � 0.28 mmol m2 h-1 following rehydration. A third model gas-phase system is non-photosynthetic CO absorption by Clostridium ljungdahlii in composites generated by aerosol or ink-jet deposition.  SEM images of rehydrated composite microstructures reveal the distribution of concentrated cells on the surface and between paper fibers allowing perfusive flow through the matrix. Various deposition methods can be used (convective sedimentation assembly, dielectrophoresis, aerosol, ink-jet printed 3-D microstructures) to generate cell monolayers, multi-layers or high surface areas microstructures containing a high volume fraction of microbes. Combining different microbes into multi-functional biocomposites is also possible.  This will enable using microbes for gas cleaning/recycling or gas-phase carbon bioprocessing utilizing a combination of engineered microbes (photosynthetic + non-photosynthetic).

Cellular composite materials for energy and gas-phase biocatalysis

247th National Meeting (2014)

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