Mass Transfer and Kinetic Limitations During Synthesis Gas Fermentation by Acetogenic Bacteria

Abstract

Hydrogen and carbon monoxide, sparingly soluble gases are transferred to reactive sites inside cells during fermentation of synthesis gas to fuel and chemicals. The rate of conversion is set by either the transfer of gas into the cell or the kinetics of reaction inside the cell. Gas consumption, cell growth and production of ethanol and acetic acid from synthesis gas, primarily CO, H2 and CO2, by Clostridium ragsdalei, also called Clostridium strain P11 was followed to observe the interplay of kinetic and mass transfer limitations in the course of fermentation. Fermentations were studied under various conditions of pressure, cell concentration, agitation, gas composition, and mass transfer techniques. Mass transfer limitation was differentiated from kinetic limitation in batch bottle fermentation. Substrate uptake rate limit transitions from kinetic limitation with inhibition to mass transfer limitation in batch bottle fermentors. Fermentation during stationary growth phase was kinetic limited. Control strategy balancing mass transfer limitation and kinetic limitation of fermentation will be adapted to a stirred tank fermentor.