Heat-loving bacteria could lead to next-generation microbe

By Holly Jessen | July 03, 2012

Key proteins have been identified in a family of bacteria that help the microbes grab onto pieces of plant material in order to better degrade it. This was discovered during the examination of eight related species of bacteria belonging to the genus Caldicellulosiruptor, which are well known for their ability to work at high temperatures. “These [bacteria] will do their thing, so to speak, at temperatures of 70 degrees Celsius and in some cases even higher,” said Paul Gilna, director of the DOE’s BioEnergy Science Center, which provides support for multidisciplinary, multi-institutional research teams, such as the one that completed this study. “Those are the kinds of temperatures that pretty much kill off a lot of other processes or enzymes so the ability to work at this high temperature is pretty important.”

North Carolina State University, Oak Ridge National Laboratory and the University of Georgia found that, among Caldicellulosiruptor bacteria, some contain a previously uncharacterized group of proteins called adhesins, which helped researchers understand why certain bacteria were better at breaking down plant material than others. An article co-authored by 18 researchers has been published on the subject online in the Journal of Bacteriology. "Previously, we knew these bacteria would secrete enzymes that would then freely diffuse into their environment," said NCSU's Sara Blumer-Schuette in a prepared statement. "We assumed that the enzymes would by chance stick to either cellulose or a piece of biomass in their environment and start to degrade it. Now we're seeing that a lot of proteins are involved in maintaining a tight interface between the bacterium and cellulose." 

Currently, cellulosic ethanol production involves three steps, including pretreatment, enzymes and yeast. Gilna said researchers want to examine microbes that are already naturally capable of digesting plant material, such as those studied for this research, and engineer them to also have the ability to ferment the sugars they release into biofuels, initially ethanol. This is referred to as consolidated bioprocessing, or CBP. An alternative approach would be to engineer cellulosic capabilities into a microbe that already naturally ferments sugars into ethanol, which he referred to as a next-generation CBP microbe. “The goal here is to drive down the cost of producing biofuels from lignocellulosic sources,” he said.