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

Abstract

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-1 .m-2) 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.

Bio-based platform chemicals synthesized from lignin biorefinery

“…Most common usage scenarios of membrane separation in in situ separation occur in the field of lignin electrochemical or enzyme biorefinery owing to the ease of configuration of the reactor and the mildness of the reaction conditions. [266][267][268] In enzymatic depolymerization of lignin, the in situ membrane separation of lignin fragments effectively prevents the repolymerization. Additionally, reaction equilibriums were altered, favoring the lignin depolymerization.…”

“…Additionally, reaction equilibriums were altered, favoring the lignin depolymerization. 268 It is well-known that membrane fouling is an omnipresent challenge in membrane applications. To mitigate this issue, a composite electrode mixer, which integrated a rod electrode with a 3D-printed static mixer, was developed in lignin electrochemical conversion.…”

“…However, the case of membrane separation in in-situ separation is not prevalent as that in ex-situ separation, potentially attributing to the harsh environment of reaction system. Most common usage scenarios of membrane separation in in-situ separation occurs in the field of lignin electrochemical or enzyme biorefinery due to the ease of configuration of the reactor and the mildness of the reaction conditions [266][267][268] . In enzymatic depolymerization of lignin, the in-situ membrane separation of lignin fragments effectively prevents the repolymerization.…”

“…In enzymatic depolymerization of lignin, the in-situ membrane separation of lignin fragments effectively prevents the repolymerization. Additionally, reaction equilibriums were altered, favoring the lignin depolymerization 268 . Still, it is well-known that membrane fouling is an omnipresent challenge in membrane applications.…”

Enhanced depolymerization of beech wood lignin and its removal with peroxidases through continuous separation of lignin fragments

“…33 Recently, a membrane bioreactor that was designed for a laccase-catalyzed reaction by Steinmetz et al successfully shifted the technical lignin reaction from polymerization to depolymerization. 34 In the membrane bioreactor, reactive lignin fragments generated by laccase were continuously isolated from the reaction system, which reduced the repolymerization reaction and enhanced the efficiency of lignin depolymerization. This approach is also expected to be favorable for a peroxidase-catalyzed reaction.…”