Novel MS-based analytical approaches for shotgun lignomics and quantification of lignin

• Applicant: Professor Dr. Dietrich Volmer
• Subject Area: Analytical Chemistry
• Term: from 2013 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 242673274

The goal of this grant renewal application is the development of novel mass spectrometric techniques for lignomics research. The lignome in this context is the full complement of lignin-related compounds in a given sample; that is, all lignin monomers, oligomers and polymers. Lignin is a major component of woody plants and second most abundant natural polymer. It is difficult degrade by chemical or biochemical methods. Depolymerization, however, is extremely important for recovery of value chemicals and biofuels from lignin wastes. During the first funding phase, we have developed novel electrochemical methods for lignin cleavage by means of ionic liquids and efficient catalytically-active electrodes. Mass spectrometric (MS) analysis showed that electrochemical degradation yielded a very large number of breakdown products, typically >5000 compounds, which could be readily characterized and assigned to chemical classes by means of ultra-high resolution MS. We developed powerful two-dimensional visualization tools that provided detailed information on the transformation and exact degradation mechanisms as well as on the identity of the cleavage products. Despite the powerful approach, MS is not yet capable to characterize full lignomes and also exhibits shortcomings for analysis of very low abundant species as well as isomers and isobars. In this grant renewal application, novel shotgun MS methods will be developed that dig much deeper into the lignome than presently possible and also yield quantitative information on lignin subunits. In particular de novo lignin sequencing is currently very difficult because of the heterogenous nature, the crosslinking and the lack of linear repeat patterns, limiting the technique currently to selected, small oligomers. We are planning comprehensive experiments by means of novel tandem-MS techniques, so-called “electron-activated dissociations (ExD)”, and expect detailed information on the different linkages of lignin subunits and thus enhanced lignin sequencing. To obtain even better sequence coverage, our strategy also comprises ion mobility spectrometry separations, to separate the numerous isomers and isobars prior to MS analysis. Finally, by developing enhanced data mining strategies for the complex mass spectral raw data, we will develop new quantitative tools that avoid the problems of existing wet chemistry procedures and permit improved quantitative determination of lignin subunits.

• DFG Programme: Research Grants