This report describes results toward developing a process to sequester CO2 centered on the enzyme pyruvate carboxylase. The process involves the use of bacteria to convert CO2 and glucose as a co-substrate and generates succinic acid as a commodity chemical product. The first phase of this research has focused on strain development and on process development. Progress in strain development has been made in three areas. The gene encoding for alcohol dehydrogenase has been knocked out of the bacteria, and thereby eliminating the synthesis of the by-product ethanol. The gene for glucokinase has been overexpressed in the production strain with the goal of faster utilization of glucose (and hence CO2). Efforts have continued toward integrating pyruvate carboxylase gene (pyc) onto the E. coli chromosome. Progress in process development has come in conducting several dozen fermentation experiments to find a defined medium that would be successful for the growth of the bacteria, while permitting a high rate of CO2 utilization in a subsequent prolonged production phase. Using this defined medium, the strains that continue to be constructed are being compared for CO2 utilization, so that we may understand the factors that govern the biological sequestration process.
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