Making Succinate More Successful

What does the word “fermentation” bring to mind? Beer? Bread? Ethanol derived from corn and other plant matter? How about succinate? Since 2001, biochemist George Bennett and bioengineer Ka-Yiu San, both professors at Rice University, have been tinkering with Escherichia coli to coax it to convert sugars to succinate, a chemical with multiple industrial uses. Now their efforts are bearing fruit as “green” succinate is starting to become a reality in chemical commerce. Who uses succinate? By itself, succinate is used as a flavor enhancer in food products and as a stabilizer in pharmaceuticals. It is also used to produce other industrial chemicals, including butanediol, tetrahydrofuran, and pyrrolidone, which become ingredients in solvents, paints, deicers, plastics, fuel additives, fabrics, and carpets. Succinate is traditionally manufactured from petrochemicals through expensive processes. The Rice team’s goal is to make a more environmentally friendly succinate from renewable starting materials. “We want to use agricultural materials that are renewable to make this useful product, and alleviate the drain of limited oil reserves,” says Bennett. The Department of Energy (DOE) “sees a future for biorefineries that use biomass as feedstocks to make fuels and chemicals,” says department chemist Gene Petersen. In 1994, the agency’s now-defunct Alternative Feedstocks Program assessed the likelihood of making chemicals from biomass. “The category of compounds that seemed most viable were organic acids like succinic, acetic, and citric,” says Petersen. That evaluation resulted in the DOE’s funding of fermentation research programs at national laboratories and universities. In 2004, the DOE released volume I of a report titled Top Value Added Chemicals from Biomass, coauthored by Petersen (volume II is expected out in 2006). According to the report, succinate tops the list of 12 “building block” chemicals—molecules with multiple functional groups that possess the potential to be transformed into new families of useful materials—that can be produced from sugars via biological conversion. In 2001, 10 million pounds of succinate were produced from petrochemicals and sold for an average of $2 per pound. “The market is there if we can make succinate more economically through biofermentation,” says Praveen Vadlani, principal research scientist at AgRenew Incorporated in Manhattan, Kansas. By making green succinate in bulk—a potentially cheaper material with the cachet of environmental friendliness—people may even be inspired to find new applications for it, such as bio-based polymers and composites, predicts Vadlani.