(519e) One-Step Extraction of Multifunctionalized Lignins from Biomass

Lignin, one of the main components of biomass, is a promising feedstock to replace aromatic materials that are currently sourced from non-renewable fossil oil. However, the industrial use of lignin in material application remains limited¹. This can partially be explained by the uncontrolled side-reactions that happen on the lignin during traditional extraction methods, which despite providing lignin at high yields, irreversibly change its structure. The poor control on the chemical functionalities is what ultimately hinders lignin’s further upgrading². We have recently demonstrated that with the Aldehyde Assisted Fractionation (AAF) it is possible to overcome the trade-off between lignin’s isolation yields and structure preservation³. Moreover, when multifunctional aldehydes are employed, lignin can also be functionalized in a controlled manner⁴.

Here, we show how this concept can be expanded to simultaneously extract and introduce more than one non-native functional groups on the lignin backbone. We functionalized the lignin with aldehydes by using terephthalaldehyde (TALD), and carboxylic acids by using glyoxylic acid (GA). First, we isolated several lignins by performing AAF with increasing ratios of TALD and GA, and then we quantified the introduced functional groups with several spectroscopic techniques. The results clearly showed that the TALD/GA ratio initially used for the AAF linearly correlated with the TALD/GA ratio measured on the isolated lignin.

The different functionalities of TALD/GA lignins were then employed to improve the mechanical properties of gelatin-based hydrogels. This lignin with two distinct and controlled non-native functionalities can in fact be used to impart multiple features to the lignin. For example, the carboxylate groups imparted water solubility to the lignin, while the aldehyde functionalities acted as a chemical crosslinker in the gelatin-lignin adduct.

Overall, we demonstrated that multifunctional lignins can be designed according to their final application and subsequently extracted in a controlled way and in high yields in one single step from lignocellulosic biomass. The ultimate goal will be to integrate these lignins into novel materials for high-end applications.

References:

1 V. Romhányi, D. Kun and B. Pukánszky, ACS Sust. Chem. Eng., 2018, 6, 14323–14331.

2 S. Bertella and J. S. Luterbacher, Trends in Chemistry, 2020, 2, 440–453.

3 L. Shuai, M. T. Amiri, Y. M. Questell-Santiago, F. Héroguel, Y. Li, H. Kim, R. Meilan, C. Chapple, J. Ralph and J. S. Luterbacher, Science, 2016, 354, 329–333.

4 S. Bertella and J. S. Luterbacher, Green Chem., 2021, In revision.