In-situ extraction of depolymerization products by membrane filtration against lignin condensation.

Catalytic depolymerization of lignin is a challenging process due to competitive repolymerization reactions. In this paper, the oxidative depolymerization of lignin was catalyzed by a commercial laccase both in a batch experiment and in a membrane bioreactor using the same catalytic conditions. The membrane bioreactor was previously optimized to reach high permeation flux (25 L.h.m) during lignin diafiltration. While the lignin was exclusively condensed in the batch experiment leading to high molecular weight macromolecules (from 9 to 16 kDa), its depolymerization was effective in the bioreactor producing fragments of less than 1 kDa thanks to the in-situ extraction of the reaction products. This paper demonstrates that the reactor configuration is playing an essential role in triggering or preventing lignin condensation. It also reports the first proof-of-concept demonstrating that in-situ membrane extraction of the reactive fragments of lignin from the bulk medium can be useful against detrimental repolymerization reactions.