BIOFUEL BREAKTHROUGH

BESC scores a first with isobutanol directly from cellulose
March 7, 2011 (Oak Ridge National Laboratory)

"In the quest for inexpensive biofuels, cellulose proved no match for a bioprocessing strategy and genetically engineered microbe developed by researchers at the Department of Energy's BioEnergy Science Center.

"Using consolidated bioprocessing, a team led by James Liao of the University of California at Los Angeles for the first time produced isobutanol directly from cellulose..."

Is this the dream realized? (slide from Caltech Prof Frances Arnold - click to enlarge)

"…[Metabolic Engineering of Clostridium Cellulolyticum for Isobutanol Production from Cellulose], published online in Applied and Environmental Microbiology, represents across-the-board savings in processing costs and time, plus isobutanol is a higher grade of alcohol than ethanol…because [it has] an energy density, octane value and Reid vapor pressure - a measurement of volatility - that is much closer to gasoline…

"While cellulosic biomass like corn stover and switchgrass is abundant and cheap, it is much more difficult to utilize than corn and sugar cane. This is due in large part because of recalcitrance, or a plant's natural defenses to being chemically dismantled…[and] biofuel production that involves several steps - pretreatment, enzyme treatment and fermentation - is more costly than a method that combines biomass utilization and the fermentation of sugars to biofuel into a single process."

slide from Caltech Prof Frances Arnold - click to enlarge

"To make the conversion possible, Liao and postdoctoral researcher Wendy Higashide of UCLA and Yongchao Li and Yunfeng Yang of Oak Ridge National Laboratory had to develop a strain of Clostridium cellulolyticum, a native cellulose-degrading microbe, that could synthesize isobutanol directly from cellulose…[because] some Clostridium species produce butanol…[but] do not digest cellulose directly…[other] Clostridium species digest cellulose but do not produce butanol…[and none] produce isobutanol…

"…[T]he research team ultimately chose Clostridium cellulolyticum, which was originally isolated from decayed grass…[which has] natural cellulolytic activity and…[produces more] alcohol than ethanol…[The] Clostridium cellulolyticum has been genetically engineered to improve ethanol production, and this has led to additional more detailed research…"