S22: Miniature Gas-Phase Coating or Microbial Paper Bioreactors for Screening Photosynthetic and Gas Fermenting MIcroorganisms

Miniature tube bioreactors containing dried and rehydrated bionano coated papers or highly concentrated microbes entrapped within paper (microbial papers) are useful for rapid screening of microorganisms in contact with a gas-phase to determine specific gas assimilation rates.  These inexpensive small bioreactors of concentrated non-growing microorganisms improve gas-liquid mass transfer, minimize liquid volume (increase product concentration) and the paper pores can separate soluble products - products accumulate in the bulk liquid phase at the bottom of the tube. CO₂ absorption without cell outgrowth has been monitored for >500 hours from cellular coatings of five strains of cyanobacteria coated by extrusion 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 and confocal 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. Other deposition methods can also be used (convective sedimentation assembly, dielectrophoresis, aerosol, ink-jet) to generate cell monolayers, multi-layers or high surface area 3-D printed microstructures from emulsions containing a high volume fraction of microbes. Combining different microbes into multi-layered biocomposites is also possible.  This will enable using microbes for gas cleaning or gas-phase carbon recycling utilizing a combination of engineered microbes (photosynthetic + non-photosynthetic).