SUNY researchers optimizing efficient biobutanol pathway

By Bryan Sims | May 26, 2011

A team of researchers at State University of New York (SUNY) College of Environmental Science and Forestry are experimenting with different strains of microorganisms to efficiently ferment sugars, extracted from woody biomass, into biobutanol and other biochemicals.

Led by Shijie Liu, associate professor at the ESF, the research involves separating hemicellulose found in fresh hardwood, mostly sugar maple species, through hot-water extraction as solvent—commonly known as hydrolysis—without any other added chemicals. The next step, Liu explained, involves putting the fractionated hemicellulose material through a nanofiltration membrane to remove acetic acid. From there, a strain of bacterium, Clostridium acetobutylicum, is fed on the hydrolysis extraction to produce liter batches of n-butanol.

In addition to n-butanol, the sugar stream produced by Liu’s team has been successfully fermented to produce ethanol, lactic acid, and Polyhydroxyalkanoates (PHA). There is no deliberate detoxification that generates waste byproducts. The residual solid mass that contains cellulose and lignin has wide applications, including fiberboard, wood fuel pellet, pulp and paper, sugars or aromatics.

“We did some adaptations that we don’t have to go through the detoxification step as most people do,” Liu told Biorefining Magazine, adding that doing so exploits the inherent value of the sugar streams found in wood biomass.

While yield from the wood itself is much lower, as there hasn’t been much work on the complete conversion process yet from that end, Liu said that he has achieved a 22 percent yield rate from sugars extracted from hydrolysis. “It really depends on the amount of hemicelluloses found in the wood,” he said.

Liu and his students conduct their work in laboratories outfitted with an anaerobic chamber to fine-tune the selection of bacteria used in the fermentation process, and a bioreactor, in which the fermentation process occurs.

Research has been going on for about three years now, and Liu said the work aims to optimize the process to eventually go from batch to continuous. Liu’s research is supported by a $400,000 grant from the U.S. DOE and $75,000 from the New York State Energy Research and Development Authority.