In the United States, researchers at Sandia National Laboratories have engineered E. coli to convert lignin into precursors for products such as nylon, plastics, and pharmaceuticals.
Seema Singh and her team engineered genes known as lignin degraders into E. coli. While abundant, lignin has been difficult for science to use because it is the material that gives plant cell walls its strength. Singh’s team was able to lower the cost of the process by placing engineering the E. coli to be induced by lignin-derived compounds such as vanillin. Traditionally, bio refineries have had to buy high-cost inducers, lowering the viability of lignin-based processes. The solution was to “circumvent the need for an expensive inducer by engineering the E coli so that lignin-derived compounds such as vanillin serve as both the substrate and the inducer,” Singh said.
This also solved the toxicity issues. “Our engineering turns the substrate toxicity problem on its head by enabling the very chemical that is toxic to the E. coli to initiate the complex process of lignin valorization,” said Singh. “Once the vanillin in the fermentation broth activates the enzymes, the E. coli starts to convert the vanillin into catechol, our desired chemical, and the amount of vanillin never reaches a toxic level. It auto regulates,” she added.