(793a) Development of Novel Biofilm-Based Reactor Systems for Enhancing Mass Transfer in Syngas Fermentation

Syngas fermentation is a promising technology for sustainable fuels and chemicals production. However, syngas conversion efficiency is limited by the low mass transfer efficiency due to the low water-solubility of carbon monoxide (CO) and hydrogen (H₂). Bioreactor design plays an important role to enhance the mass transfer efficiency. In this study, we investigated the applicability of two biofilm-based reactor systems, hollow fiber membrane biofilm reactor (HFM-BR) and monolithic biofilm reactor (MBR), for mass transfer enhancement in syngas fermentation.  Clostridium carboxidivorans P7 was used as test strain. Both reactor systems were operated under batch condition for 15 days with continuous gas feed (20% CO, 15% H₂, 15% CO₂, 60% N₂) at 200 mL/min so that microbes could attach onto the surface of hollow fiber membrane or monolith channels. After the biofilm was formed, the continuous operation was started by continuously feeding liquid media to the reactors.  The maximum ethanol concentration in the HFM-BR and MRB achieved 24.3 g/L and 12.7 g/L, respectively. The mass transfer coefficients (K_La) of the two reactors were 1096 hr^-1 and 443 hr^-1. A conventional continuous stirred tank reactor (CSTR) and a bubble colume reactor (BCR), which have the same working conditions as the above tow bio-film based systems, were used for comparison. The results show that the ethanol production, syngas consumption from the two biofilm based systems are much higher than those of the control, due to the enhancement of the mass transfer efficiency of these two reactors.