Process intensification of gas-to-liquid bioprocessing with Clostridium ljungdahlii biocomposite reactor modules: High intensity, low power, ambient storage

We investigate Process Intensification (PI) of CO, CO₂, or CH₄ absorption using biocomposites - concentrated cell paste immobilized within paper that can be stored dry and when rehydrated the cells are reactive. Biocomposites reduce gas mass transfer resistance using thin liquid films, decrease water consumption and reduce power input. C. ljungdahlii OTA1, takes up CO/H₂ and produces ethanol/acetate. OTA1 adheres to chromatography paper at 10¹² CFU/m². Biocomposites are tested in shaking horizontal Balch tubes, hydrated with growth limiting media, and flushed with H₂/N₂/CO (45%/10%/45%). The hydrated coating is in the gas phase covered with a thin liquid film (thickness ~30µm). At 25rpm shaking (97% power reduction from 100 rpm) the CO specific uptake rate of an OTA1 biocomposite is ~300% faster than suspended OTA1. The biocomposite establishes a high interfacial area without vigorous liquid mixing in contrast to a stirred tank reactor (STR). A specific CO consumption PI of 14 fold is demonstrated (101 mmol CO/m²/h) over previous results. The biocomposite k_La apparent of ~100 h^-1 at <10 W/m³ power input compares favorably with a STR (k_La of ~100h^-1 at ~1000W/m³). The specific CO uptake of ~25mmol CO/g_DCW/h with low power input is comparable to the specific uptake for C. ljungdahlii of ~35mmol CO/g_DCW/h in a STR. Further optimization (porosity, surface area/reactor volume, cell loading) will enhance performance. A prototype falling film reactor demonstrated a k_La as high as ~1000h­^-1. C. ljungdahlii biocomposites can be vacuum dried (25in Hg, 60min) and stored at 21ºC under Argon with <3% relative humidity.