The lignin component of biomass is an attractive source of carbon and energy for the microbial production of fuels and chemicals. This adding of value (valorization
) to lignin by biological conversion can increase the overall economic viability of biorenewable fuel and chemical production. Thermal depolymerization of biomass through fast pyrolysis shows promise in terms of its ability to recover aromatic monomers from the lignin component of the biomass. Specialized microbes, such as Pseudomonas putida
KT2440, can utilize many of these aromatic monomers when provided in pure culture [1,2]. However, microbes can be negatively affected by toxic impurities in biomass derived streams, and lignin rich pyrolysis fractions are insoluble in water and therefore inaccessible to microbes in liquid culture medium. Here we addressed these toxicity and insolubility issues by developing and testing an emulsion formula which granted P. putida
KT2440 access to the phenolic monomers. The optimized emulsion formula contained 18.2 MΩ water, a 70:30 ratio of Tween20®
surfactant, and the lignin rich pyrolysis fraction. P. putida
KT2440 was able to use this emulsion formulation as sole carbon source. Additionally, studies with a pure aromatic monomer, p-coumarate, indicated that the emulsion procedure at least partially protects P. putida
KT2440 from the substrate toxicity of this monomer. To minimize surfactant cost, the surfactant amount was minimized to 7 wt% of the total lignin rich pyrolysis fraction weight. This emulsification method is an important step in enabling the biological valorization of biomass-derived lignin.
Refs: 1. Johnson, C. W.; Beckham, G. T. Metabolic Engineering 2015, 28, 240-247. 2. Vardon, D. R.; Franden, M. A.; Johnson, C. W.; Karp, E. M.; Guarnieri, M. T.; Linger, J. G.; Salm, M. J.; Strathmann, T. J.; Beckham, G. T. Energy & Environmental Science 2015, 8, (2), 617-628.