Maximizing the production of high-value chemicals via fast-pyrolysis of lignin-engineered poplars: Impact of cinnamyl alcohol dehydrogenase 1 (hpCAD) downregulation

Lignin valorisation is crucial for the economic viability of biorefineries, but remains a challenge. Our work shows that the fast pyrolysis of transgenic biomass has significant potential for the production of high-value chemicals. New field-grown transgenic poplars severely downregulated for cinnamyl alcohol dehydrogenase 1 (hpCAD) have a change in lignin structure due to the substantial incorporation of sinapaldehyde into the polymer. Wildtype and hpCAD poplars were pyrolyzed in a micropyrolyzer for identification and quantification of pyrolytic volatiles. The study aims at capturing the influence of CAD1 downregulation on lignin-derived pyrolysis products supported by statistical analysis of the obtained pyrolysis data. The results showed that the pyrolysis of hpCAD lines enhanced the yield of two kinds of high-value aromatics, namely, those with C--O group in side-chains (e.g. vanillin and syringaldehyde), and those without side-chains (e.g. phenol, guaiacol and syringol), at the expense of the formation of aromatics with alkyl side-chains.

Automated summary

The fast pyrolysis of transgenic biomass has the potential to produce high-value chemicals, which is crucial for the economic viability of biorefineries. Our study shows that downregulation of CAD1 in transgenic poplars leads to changes in lignin structure, resulting in increased yield of aromatics with C-O groups and decreased yield of aromatics with alkyl side-chains during pyrolysis.