(639b) Enabling Microbial Utilization of Lignin-Derived Monomers

Authors: 
Davis, K., Iowa State University
Rover, M. R., Iowa State University
Salvachua, D., National Bioenergy Center, National Renewable Energy Laboratory
Jarboe, L., Iowa State University
Beckham, G. T., National Renewable Energy Laboratory
Wen, Z., Iowa State University
Smith, R. G., Iowa State University
Brown, R. C., Iowa State University
Bai, X., Iowa State University
Xue, Y., Iowa State University
Biomass contains lignin, a polymer of phenolic molecules, which provides stability and protection to the plant. Many economic models indicate that the addition of value to lignin is essential for the economic viability of the conversion of biomass to renewable fuels and chemicals. Some microorganisms, such as Pseudomonas putida, can convert or metabolize some aromatic and phenolic molecules. Previous reports have shown that P. putida can be engineered to funnel multiple phenolics through its central metabolic pathways [1]. A funneling approach can be advantageous because thermally decomposed lignin can be composed of hundreds of different molecules many of which can be aromatic or phenolic in nature. We have identified the following phenolics in our thermally decomposed lignin: phenol, guaiacol, 2-ethyl phenol, 4-ethylguaiacol, 4-vinylphenol, 4-vinylguaiacol, syringol, and vanillin. Phenolic-rich fractions of pyrolyzed biomass have low solubility and therefore cannot be easily accessed by microorganisms in aqueous cultures. In addition, microorganisms can be negatively affected by inhibitors present in processed biomass streams. Here, we have developed emulsions of phenolic monomer-rich product using surfactants or sonication. Pseudomonas putida KT2440 grew in emulsions produced using surfactants and phenolic monomer-rich product. Studies suggest that the emulsion allowed P. putida to access molecules with low solubility in aqueous culture. In addition, the emulsion produced using surfactants seemed to have an additional benefit of decreasing the toxic effects of the phenolic molecule p-coumarate. P. putida also grew in emulsions of the phenolic monomer-rich product produced by sonication. The total carbon decreased over time indicating that P. putida was metabolizing components of the phenolic monomer-rich product. Ongoing work involves tuning the pyrolysis products to match the products preferred by P. putida. In addition, P. putida will also be engineered to better funnel the products present in the pyrolysis stream.

Refs: 1. Johnson, C. W.; Beckham, G. T. Metabolic Engineering 2015, 28, 240-247.