Rice stands to gain from biobutanol

Rice stands to gain from biobutanol’s return

Rice News staff

With oil prices high and every indication that they’ll stay that way, policymakers and energy executives are finally beginning to invest — both financially and politically — in biofuel alternatives.

U.S. ethanol production will expand by more than 30 percent this year with the opening of 60 new plants. Investors are also flocking to biodiesel, with dozens of plants planned nationwide, including two in the Houston-Galveston region.

Jeff Fitlow
Rice biochemist George Bennett, right, and graduate student Leighann Sullivan are working in the lab to find ways to improve the biofuel biobutanol, a lesser-known — and possibly better — cousin of ethanol.

Nearly a dozen research groups at Rice are actively looking for ways to improve biofuels, including ethanol and biodiesel, but Rice has significant scientific contributions from more than 20 years of groundbreaking studies into a third, lesser-known fuel called biobutanol, which could turn out to be even more promising than it’s better-known siblings.

Like ethanol, biobutanol is made from plant feedstocks like corn, potatoes and molasses, and like ethanol it can be mixed with gasoline, either to reduce smog or to stretch a gallon of gas. Unlike ethanol, biobutanol can be transported in pipelines and contains about 30 percent more energy, so it can be substituted for unleaded gas in mixtures approaching 100 percent — without engine modifications.

“In a nutshell, we think it’s better,” said Leighann Sullivan, a graduate student in the lab of Rice biochemist George Bennett, who has published more than 50 scientific papers on biobutanol.

Apparently, BP and DuPont think so too. The companies announced plans in June to convert an ethanol plant in the United Kingdom to biobutanol production early next year.

Bennett said the announcement brings biobutanol full circle; not only is it the latest biofuel to enter the market, but it was also one of the first chemicals made by fermentation.

Its origins date to World War I, when British chemist Chaim Weizmann discovered how to use industrial-scale fermentation to produce massive quantities of acetone needed to supply British troops with ammunition. The discovery made Weizmann famous as the father of industrial fermentation — an achievement that not only helped Britain win the war but which eventually played a crucial role in birthing the modern pharmaceutical industry.

The key to Weizmann’s acetone-manufacturing scheme was a bacterium called Clostridium acetobutylicum. Found naturally in soils, C. acetobutylicum feeds on dead plants and aids in decomposition. Its three primary waste byproducts are butanol, acetone and ethanol. An important feature of C. acetobutylicum is its ability to grow on a wide variety of substances, including agricultural crops like molasses and potatoes, and Weizmann’s factories were fed with a range of these. But butanol can also be made from petroleum, and cheap oil eventually led to the shuttering of all the Weizmann factories. The last of them operated in the former Soviet Union and South Africa in the 1980s.

Though solvent-producing bacteria were well-known to biologists, the biochemical processes were little studied until the late Fred Rudolph, Terry Papoutsakis and Bennett began systematically exploring them at Rice in the 1980s.

“Many of the enzymes were isolated by Fred and collaborators, and all of the solvent-producing genes were isolated at Rice,” Bennett said. “Fred, Terry, who’s now at Northwestern, and I conducted many experiments on knockouts and other mutants in the late 1980s and 1990s.”

Rice’s team was also a major supplier of DNA and live cultures to the consortium of scientists who sequenced the genome of C. acetobutylicum in the mid 1990s, and Rice’s work has continued, even after Rudolph’s untimely death in 2003.

“This organism is more difficult to work with than yeast or E. coli, so a significant amount of work has gone into developing the biotechnological tools needed to manipulate it,” Bennett said.
Bennett and collaborators have developed a mutant strain of the bacterium that produces about one-third more butanol than naturally occurring strains, and they hope to do even better. Eventually, Bennett hopes Rice’s work will allow biobutanol producers to improve yields and make biobutanol even more competitive with petroleum-based butanol.

“Everything is falling into place for biobutanol; the economics, the move toward ‘green’ chemistry and the maturing science,” Bennett said.

About Jade Boyd

Jade Boyd is science editor and associate director of news and media relations in Rice University's Office of Public Affairs.