Effect of CO Transfer on Hydrogen Production By Carboxydotrophic Archeon Thermococcus Onnurineus NA1

In recent years biological conversion of syngas or steel mill gas containing carbon monoxide (CO) has been receiving much attention since it offers an exciting opportunity to produce fuels and chemicals from non-food and non-fossil resources. However, there are some obstacles for the commercialization of this process. One major bottleneck is regarding the CO transfer since it has the poor aqueous solubility and it is important to design a strategy to enhance gas transfer efficiency. In this study, the effect of CO transfer on the performance of syngas fermentation was investigated. Hydrogen production by Thermococcus onnurineus NA1, a carboxydotrophic hyperthermophilic archeon using a model gas containing 60% of CO was carried out at 80 ^oC in a stirred tank reactor with Rushton turbine impeller. Reactor performance with various agitation speeds and CO flow rate was evaluated in terms of cell growth and hydrogen productivity. After short lag period depending on agitation speed and CO flow rate, T. onnurineus NA1 actively produced hydrogen with growth–associated kinetics, governed by Luedeking-Piret model. Severe mass transfer was occurred within several hours and hydrogen productivity remained constant. From mass transfer coefficient of CO, determined using the hydrogen productivity in the mass transfer limiting stage, we derived a correlation equation between CO transfer and reaction conditions.