JBEI researchers develop dynamic sensor-regulatory system

By Erin Voegele | April 05, 2012

Researchers at the U.S. DOE’s Joint BioEnergy Institute have developed a new technique that can significantly boost the microbial production of biofuels. The new technique, referred to as a dynamic sensor-regulator system (DSRS), was able to triple the amount of biobased diesel produced from glucose in one demonstration. According to information released by Lawrence Berkeley National Laboratory, which is part of the JBEI, the DSRS system is able to detect metabolic changes in microbes during the production of fatty acid-based fuels or chemicals and control the expression of genes affecting that production.

“Microbial production of fuels and chemicals from fatty acids is a greener and sustainable alternative to chemical synthesis,” JBEI researcher Fuzhong Zhang. “However, high productivities, titers and yields are essential for microbial production of these chemical products to be economically viable, particularly in the cases of biofuels and low-value bulk chemicals.”

Zhang explained that traditional microbial production of fatty-acid based fuels and chemicals have been limited by metabolic imbalances that result in the bioreactor. When pathway genes are expressed at levels that are too low, he said that it results in low yields and a “bottleneck” in the process. However, when the expression is too high, resources are diverted to produce unnecessary intermediate metabolites or enzymes. As those unnecessary metabolites and enzymes accumulate, it can prove toxic to the microbe, which essentially halts production of the target fuel or chemical.

The DSRS system is able to overcome these changes. It does this by responding to the metabolic status of the microbe as it converts feedstock into biobased products by sensing key intermediate metabolites in an engineered pathway. It can then regulate genes that control the production and consumption of intermediates, thereby optimizing productivity as conditions within the bioreactor continue to change.

According to information released by Berkeley Lab, Zhang and his team created the DSRS using a strain of E. coli that had been engineered at JBEI to produce biobased diesel. When the DSRS was introduced to the strain its stability was improved and yields were increased. According to Zhang, his team intends to continue this line of research. “We are aiming to develop more DSRS systems,” he said, “focusing not only on the production of diesel fuel, but expanding the focus to other biobased fuels and chemicals.”