S127: Intensifying and stabilizing whole cell biocatalysts using coatings, inks and reactive papers

Non-growing whole cell biocatalysts can be intensified and stabilized by entrapment in thin (<50 μm thick), adhesive, nanoporous polymer coatings or in nonwovens that can be stored dry.  When rehydrated, microbial biocoatings or papers are capable of protein synthesis, chiral oxidations, carbon assimilation, gas absorption or photoreactivity, all without significant outgrowth. We investigate these advanced materials to intensify multi-phase bioreactors, microbial photoabsorbers, biomembranes or biophoto fuel cells.  Biocoatings contain microbes growth-limited by a nitrogen source, however, little is known about the regulation of protein synthesis or how cells survive desiccation and osmotic stress during drying.  Reactivity depends on microbial survival (loss of viability during drying, dry storage, rehydration), microstructure (nanoporosity, adhesion, cell packing), physical intensification (cell density/surface area), specific reactivity, thinness, and pore structure.  Up-regulation of gene expression of the microbes allows coatings to sense or “self-tune”.  We engineer monolayer or multi-layer coatings deposited onto flexible nonporous or porous substrates by continuous convective assembly (CCA), dielectrophoresis (DEP) and other methods.  CCA orders cells by evaporation of the meniscus; microstructure is affected by evaporation rate, sedimentation, particle or cell properties (size, density, buoyancy, charge) and convective transport.  DEP aligns microbes in an electric field as charged polarizable particles.  Model systems are: photo H₂ production by Rhodopseudomonas palustris, gas-phase CO₂ adsorption and O₂ evolution by Chlamydomonas reinhardtii or Synechococcus, and gas-phase CO absorption by Clostridium ljungdahlii. These systems reveal how coating and paper microstructure can be optimized for transport, reactivity, and biocatalyst stability - half lives of 100s to 1,000s of hours.