Process intensification (PI) of CO consumption by C. ljungdahlii in a low power input biocomposite gas absorber

PI in a cellular biocomposite concentrates cells, reduces mass transfer resistance using thin liquid films, decreases water consumption and can significantly reduce power input for carbon recycling into fuels and chemicals. Our model system, C. ljungdahlii OTA1, takes up CO/H₂ and produces ethanol/acetate. The cells will adhere to chromatography paper without the use of an adhesive at 10¹² CFU/m². These biocomposites are tested in horizontal Balch tubes, hydrated with growth limiting media, and flushed with an H₂/N₂/CO mixture (45%/10%/45%). The biocomposite is hydrated by the media moving through the paper pores while the coating remains in the gas phase. Using an extrusion coating method, at 100rpm the CO specific uptake rate of OTA1 is ~10% faster in a biocomposite than in suspension. However, at 25rpm (98% less power) the biocomposite is ~300% faster. This is the result of the paper maintaining a high interfacial area without vigorous mixing which is required for high CO uptake in a stirred tank. A specific CO consumption PI of more than an order of magnitude is demonstrated (6.6 vs 69.8 mmol CO/m²/h) over previous researchers (Gosse et al, 2012). The current k_La_apparent of this system compares favorably with common bioprocessing technologies. However, further microstructure optimization could enhance low power biocomposite gas absorber performance. We also investigate the desiccation tolerance of OTA1 by adding excipients and controlling the drying, storage and rehydration conditions on paper for rapid recovery of reactivity to create a continuous gas-absorbing module that can be stored dry at ambient conditions.