Process Design for the Biocatalysis of Value-Added Chemicals from Carbon Dioxide

摘要

This report describes results toward developing a process to sequester CO{sub 2} centered on the enzymes PEP carboxylase and pyruvate carboxylase. The process involves the use of bacteria to convert CO{sub 2} and glucose as a co-substrate and generates succinic acid as a commodity chemical product. The study reports on strain development and process development. In the area of strain development, knockouts in genes which divert carbon from the enzymatic steps involved in CO{sub 2} consumption were completed, and were shown not to affect significantly the rate of CO{sub 2} sequestration and succinic acid generation. Furthermore, the pyc gene encoding for pyruvate carboxylase proved to be unstable when integrated onto the chromosome. In the area of process development, an optimal medium, pH and base counterion were obtained, leading to a sequestration rate as great as 800 mg/Lh. Detailed studies of gas phase composition demonstrated that CO{sub 2} composition has a significant affect on CO{sub 2} sequestration, while the presence of 'toxic' compounds in the gas, including NO{sub 2}, CO and SO{sub 2} did not have a detrimental effect on sequestration. Some results on prolonging the rate of sequestration indicate that enzyme activities decrease with time, suggesting methods to prolong enzyme activity may benefit the overall process.