A Versatile Method for Preparation of Hydrated Microbial-Latex Biocatalytic Coatings for Gas Absorption and Gas Evolution

We describe a latex wet coalescence method for gas-phase immobilization of microorganisms on paper which does not require drying for adhesion. This method reduces drying stresses to the microbes. It is applicable for microorganisms that do not tolerate desiccation stress during latex drying even in the presence of carbohydrates. Small surface area, 10-65 lm thick coatings were generated on chromatography paper strips and placed in the head-space of vertical sealed tubes containing liquid to hydrate the paper. These gas-phase microbial coatings hydrated by liquid in the paper pore space demonstrated absorption or evolution of H₂, CO, CO₂ or O₂. The microbial products produced, ethanol and acetate, diffuse into the hydrated paper pores and accumulate in the liquid at the bottom of the tube. The paper provides hydration to the back side of the coating and also separates the biocatalyst from the products. Coating reactivity was demonstrated for Chlamydomonas reinhardtii CC124, which consumed CO₂ and produced 10.2 ± 0.2 mmol O ₂ m^-2 h^-1, Rhodopseudomonas palustris CGA009, which consumed acetate and produced 0.47 ± 0.04 mmol H₂ m ^-2 h^-1, Clostridium ljungdahlii OTA1, which consumed 6 mmol CO m^-2 h^-1, and Synechococcus sp. PCC7002, which consumed CO2 and produced 5.00 ± 0.25 mmol O₂ m-2 h-1. Coating thickness and microstructure were related to microbe size as determined by digital micrometry, profilometry, and confocal microscopy. The immobilization of different microorganisms in thin adhesive films in the gas phase demonstrates the utility of this method for evaluating genetically optimized microorganisms for gas absorption and gas evolution.