Functional and Systems Biology
Biologically Produced Muconic Acid Can Replace Petroleum-Based Products
Researchers take a step closer to a commercially viable, sustainable alternative to fossil-fuel-based biochemical production strategies.
Scientists have identified a sustainable strategy for converting sugars into muconic acid, a common building block for bioproducts and petrochemicals. Shown here are samples from the research (on the tray at left) awaiting metabolomics analysis—large-scale study of metabolites and their processes—by high-resolution gas chromatography coupled with mass spectrometry. (Photo by Andrea Starr | Pacific Northwest National Laboratory)
The Science
Replacing conventional petrochemicals—any chemical made from crude oil, natural gas, or coal—is vital to curb human-made greenhouse gas emissions. A key strategy to this end is engineering bacterial strains that can convert sugars, such as glucose and xylose, derived from plant waste to biochemicals and biofuels at industrially relevant scales. In this study, a collaborative team from the Agile BioFoundry—a consortium of Department of Energy national laboratories—identified an efficient and sustainable strategy for converting glucose and xylose to muconic acid, a potential building block for important bioproducts and petrochemicals.
The Impact
Previous efforts to produce muconic acid from sugars have been successful, but engineering of bacterial strains has not yet achieved commercially viable performance. Now, a research team has demonstrated that using both glucose and xylose in the soil bacterium Pseudomonas putida is an efficient strategy for producing muconic acid. This method takes a significant step closer to the economic threshold for using plant sugars to produce muconic acid, opening doors for further research and overcoming current cost barriers.
Summary
Muconic acid is a valuable molecule that can be converted into a variety of bioproducts and petrochemicals for use as direct replacements for conventional petrochemicals. A new research study shows that the bacterial strain Pseudomonas putida KT2440 can be engineered to convert the lignocellulosic sugars glucose and xylose into muconic acid. To do so, a multi-institutional team of scientists used metabolic engineering in P. putida to express the D-xylose isomerase pathway, a key part of xylose conversion, followed by adaptive laboratory evolution to improve strain performance. They demonstrated that efficient muconic acid synthesis from both xylose and glucose could be enabled through increased expression of the key facilitator superfamily transporter PP_2569, overexpression of the aroB gene, and mutations in the heterologous D-xylose:H+ symporter (a cell membrane protein that can transport different molecules in the same direction across the membrane). As part of the overall effort, researchers used gas chromatography-mass spectrometry metabolomics for in-depth metabolite identification and characterization at EMSL, the Environmental Molecular Sciences Laboratory, a Department of Energy user facility located in Richland, Washington. The metabolites were confirmed using EMSL’s metabolomics database. The researchers produced 33.9 grams per liter of muconic acid at a rate of 0.18 grams per liter per hour and a 46% molar yield, which is 92% of the maximum theoretical yield. These results bring this process one step closer to commercial viability.
Contacts
Young-Mo Kim, Environmental Molecular Sciences Laboratory, young-mo.kim@pnnl.gov
Kristin Burnum-Johnson, Environmental Molecular Sciences Laboratory, kristin.burnum-johnson@pnnl.gov
Adam Guss, Oak Ridge National Laboratory, gussam@ornl.gov
Christopher Johnson, National Renewable Energy Laboratory, christopher.johnson@nrel.gov
Gregg Beckham, National Renewable Energy Laboratory, gregg.beckham@nrel.gov
Funding
Funding for this research was provided by the Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy, and by the DOE Bioenergy Technologies Office (BETO) via the Agile BioFoundry National Laboratory consortium.
Publications
Ling, C., et al, “Muconic acid production from glucose and xylose in Pseudomonas putida via evolution and metabolic engineering.” Nature Communications 13(1), 4925 (2022). [DOI: 10.1038/s41467-022-32296-y]