A Biorefinery Approach to Transforming Lignin into High-Value Products: Coupling a Microbial Electrolysis Cell and Lignin Depolymerization

Abstract:

Lignin is the largest store of renewable aromatics. Due to its refractory nature, however, its chemical potential is not fully realized. Here, we propose a biorefinery where the treatment of wastewater by a microbial electrolysis cell (MEC) produces "clean" water and a caustic catholyte that can depolymerize lignin under mild conditions into two high value product streams. We determine the MEC operating conditions to produce a depolymerization solvent and characterize and quantify solution and colloidal phase products using an array of analytical techniques. In contrast to previous reports of limited high-value-product yields, we obtain and identify 11% of discrete aromatics (monomers and flavonoids) using LC-MSn. We close mass balance by simultaneously producing lignin nanoparticles. In part, our higher product yield is due to selective repolymerization to form flavonoids and nanoparticles. Furthermore, we explore how depolymerization is influenced by lignin source (i.e. herbaceous, softwood, and hardwood) and extraction (i.e. organosolv and klason) to gain insight into ways to tune products. We also explore the effect of salt concentration, salt type, and pH on LNP properties. Both flavonoids and lignin nanoparticles have antioxidant properties and have potential applications in the pharmaceutical, nutraceutical, personal care, and agricultural industries.

Bio:

Natalia Obrzut is a fifth year Ph.D. candidate at Northwestern University working with Dr. Kimberly Gray. Natalia's work focuses largely on researching environmentally friendly ways of producing valuable products from lignin, a highly aromatic structure that is typically discarded as a low value waste. Natalia and Dr. Gray have published a book chapter and a paper and two ACS presentations. Natalia received her B.S. in both Physics and Biochemistry from Loyola University Chicago in 2018. Upon completing her Ph.D. this June, Natalia will start a career in management consulting at Bain & co. in Chicago.