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-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.

Lignin Carbohydrate Complexes structure preserved throughout downstream processes for their valorization after recovery from industrial process water.

Firstly studied and pointed out because of their major role in wood recalcitrance to delignification, LCCs are gradually raising interest about their own valorization thanks to their various interesting properties. Considering their future industrial production, this work is focused on evaluating the impact of different downstream processes (DSP) on their structure including moist heat sterilization, simple effect evaporation and spray-drying. LCCs were recovered from the mill water of a thermomechanical plant by successive membrane filtration steps. Samples were taken after the different DSP and compared to a freeze-dried control. Global and structural characterizations given by elemental analysis, acid hydrolysis, pyrolysis coupled to gas-chromatography, SEC, 13C and 2D-HSQC NMR showed that the LCCs structure is well preserved during all of these DSP. This paper demonstrates the feasibility of producing high quality industrial LCC grade for commercialization in integrated biorefineries.