Enhancing Lignin Functionality through Targeted Process Optimization
J. Bergrath*1,2, R. Burger1, H.-W. Kling2, M. Schulze1,3
1 Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
2 Department of Chemistry and Biology, University of Wuppertal, Gaußstrasse 20, 42119 Wuppertal, Germany
3 Institute of Crop Science and Resource Conservation, Faculty of Agricultural, Nutritional and Engineering Sciences, University of Bonn, Rheinbach, Germany
*jonas.bergrath@h-brs.de
Lignin, a complex aromatic biopolymer and a key structural component of plant cell walls, offers significant potential for high-value applications, such as antioxidants for packaging and food preservation.[1] The physicochemical properties of lignin, i.e. molecular weight (Mw) and the content of functional groups, are profoundly influenced by the extraction method and the biomass source.[2] This study utilizes a design of experiments (DOE) approach to optimize the organosolv process conditions for lignin extraction from grape pomace, pruning, and reed.
The experimental factors, including temperature, process time, and ethanol concentration, were systematically varied to study their effects on Mw and total phenolic content (TPC). The findings indicate that the ethanol concentration exerts a substantial influence on the Mw of both p-hydroxyphenyl, guaiacyl and syringyl (HGS) and GS lignin-containing biomass. Temperature exhibited a non-linear effect, where higher Mw lignins were increasingly isolated at lower temperatures, while higher temperatures promoted recondensation. Conversely, TPC showed the opposite trend, with a local maximum observed at approx. 170 °C. Higher ethanol concentrations (90 v/v %) and lower temperatures (150 °C) resulted in lignin fractions with higher Mw and reduced TPC.
The correlation between Mw and TPC, along with their opposing trends, indicates that extraction conditions directly influence lignin's antioxidant potential. Prediction and optimization plots suggest that lignin properties can be tailored for specific applications, by adjusting ethanol concentration and temperature. The study underscores the crucial role of precise process parameter control in enabling biomass-specific lignin extraction, thereby paving the way for environmentally friendly advanced material applications.
References
[1] Shorey, R.; Salaghi, A.; Fatehi, P.; Mekonnen, T.H. Valorization of lignin for advanced material applications: a review, RSC Sustain, 2024, 2, 804-831. DOI: 10.1039/d3su00401e
[2] Bergrath, J.; Rumpf, J.; Burger, R.; Do, X. T.; Wirtz, M.; Schulze, M. Beyond Yield Optimization: The Impact of Organosolv Process Parameters on Lignin Structure, Macromol. Mater. Eng., 2023, 308. DOI: 10.1002/mame.202300093