Development of Methods to Engineer Microbial Biocatalytic Coating Microstructure for Optimal Reactivity

Optimization of the reactivity of microbial biocatalytic coatings depends on microstructure (nanoporosity, adhesion, cell alignment or packing), physical intensification (cell density/ surface area), reduction of diffusion path (thinness, pore structure) and genetic manipulation to minimize loss of reactivity resulting from cellular stresses associated with coating, drying and rehydration.  Up-regulation of gene expression of coating-entrapped microbes can further increase reactivity and allow coatings to adapt or “self-tune” to changing conditions.  In order to optimize, model and predict the reactivity of multi-layer and multi-organism biocatalytic coatings, we study the microstructure of uniform monolayers of polymer particle + cell blends deposited onto flexible polyester by convective sedimentation assembly (CSA) and dielectrophoresis (DEP).  CSA orders cells on surfaces by evaporation of the meniscus; coating microstructure is effected by evaporation rate, sedimentation, and particle or cell properties (size, density, buoyancy, charge) and convective transport.  DEP aligns microbes in an electric field as charged polarizable particles.  CSA and DEP methods used for ordering polymer particle are  modified to screen polymer emulsion + cell blends to generate permanent cell adhesion to the substrate and preserve reactivity after drying and rehydration.  Model systems investigated are: H₂ production by Rhodopseudomonas palustris, CO₂ adsorption and O₂ evolution by  Chlamydomonas reinhardtii or Synechococcus sps. Understanding the relationships between coating microstructure and reactivity will lead to engineering highly reactive nanoporous biocatalytic coatings which incorporate both H₂ and O₂ producing microbial coatings (as fuel cells), or CO_x adsorbing coatings for recycling carbon emissions to liquid fuels or chemical intermediates.