Micropyrolysis of natural poplar mutants with altered p-hydroxyphenyl lignin content

- Analytical pyrolysis GC-MS for thermochemical degradation analysis of natural poplar mutants.
- Shift in lignin-derived compounds for mutants homozygous for the defective PnHCT1-Δ73 allele.
- Higher production of non-methoxylated products at the expense of methoxylated phenols.
- Correlation analysis revealing demethoxylation of G and S lignin units into non-methoxylated phenols.

Analytical pyrolysis coupled to GC-MS (Py-GC-MS) was applied for the thermochemical degradation analysis of wood from poplar (Populus nigra) defective in p-HYDROXYCINNAMOYL-CoA:SHIKIMATE p-HYDROXYCINNAMOYL TRANSFERASE 1 (HCT1), an enzyme essential in the biosynthesis of guaiacyl and syringyl units in lignin. The aim of this study was to assess the potential of natural poplar trees with characteristic lignin composition to improve the yield of valuable chemicals in biomass fast pyrolysis, with a focus on phenolic product formation during lignin decomposition. Analysis of the fast pyrolysis vapor phase obtained from the lignocellulosic biomass of trees homozygous for the defective PnHCT1-Δ73 allele revealed significant shifts in the spectrum of lignin-derived pyrolytic compounds as compared to wild type and heterozygous trees. More particular for the homozygotes, a higher production of the non-methoxylated p-hydroxycinnamic alcohol (p-coumaryl alcohol) and 2,3-dihydrobenzofuran was detected at the expense of mono-methoxylated phenols. Correlation analysis also suggested further decomposition reactions such as demethoxylation, demethylation and alkylation of the mono- and di-methoxylated phenolic moieties during pyrolysis, giving rise to a remarkable amount of non-methoxylated phenols in the pyrolytic spectrum.