Analytical Py-GC/MS of Genetically Modified Poplar for the Increased Production of Bio-aromatics

Gorugantu SriBala; Hilal Ezgi Toraman; Steffen Symoens; Annabelle Déjardin; Gilles Pilate; Wout Boerjan; Frederik Ronsse; Kevin M Van Geem; Guy B Marin

doi:10.1016/j.csbj.2019.04.007

Analytical Py-GC/MS of Genetically Modified Poplar for the Increased Production of Bio-aromatics

Comput Struct Biotechnol J. 2019 Apr 25:17:599-610. doi: 10.1016/j.csbj.2019.04.007. eCollection 2019.

Authors

Gorugantu SriBala¹, Hilal Ezgi Toraman¹, Steffen Symoens¹, Annabelle Déjardin², Gilles Pilate², Wout Boerjan^{3

4}, Frederik Ronsse⁵, Kevin M Van Geem¹, Guy B Marin¹

Affiliations

¹ Ghent University, Laboratory for Chemical Technology, Technologiepark 125, 9052 Ghent, Belgium.
² Institut National de la Recherche Agronomique (INRA), Unité de Recherche 0588, Amélioration, Génétique et Physiologie Forestières, 45075 Orléans, France.
³ Ghent University, Department of Plant Biotechnology and Bioinformatics, Technologiepark 71, 9052 Ghent, Belgium.
⁴ VIB Center for Plant Systems Biology, Technologiepark 71, 9052 Ghent, Belgium.
⁵ Ghent University, Department of Biosystems Engineering, Coupure Links 653, 9000 Ghent, Belgium.

Abstract

Genetic engineering is a powerful tool to steer bio-oil composition towards the production of speciality chemicals such as guaiacols, syringols, phenols, and vanillin through well-defined biomass feedstocks. Our previous work demonstrated the effects of lignin biosynthesis gene modification on the pyrolysis vapour compositions obtained from wood derived from greenhouse-grown poplars. In this study, field-grown poplars downregulated in the genes encoding CINNAMYL ALCOHOL DEHYDROGENASE (CAD), CAFFEIC ACID O-METHYLTRANSFERASE (COMT) and CAFFEOYL-CoA O-METHYLTRANSFERASE (CCoAOMT), and their corresponding wild type were pyrolysed in a Py-GC/MS. This work aims at capturing the effects of downregulation of the three enzymes on bio-oil composition using principal component analysis (PCA). 3,5-methoxytoluene, vanillin, coniferyl alcohol, 4-vinyl guaiacol, syringol, syringaldehyde, and guaiacol are the determining factors in the PCA analysis that are the substantially affected by COMT, CAD and CCoAOMT enzyme downregulation. COMT and CAD downregulated transgenic lines proved to be statistically different from the wild type because of a substantial difference in S and G lignin units. The sCAD line lead to a significant drop (nearly 51%) in S-lignin derived compounds, while CCoAOMT downregulation affected the least (7-11%). Further, removal of extractives via pretreatment enhanced the statistical differences among the CAD transgenic lines and its wild type. On the other hand, COMT downregulation caused 2-fold reduction in S-derived compounds compared to G-derived compounds. This study manifests the applicability of PCA analysis in tracking the biological changes in biomass (poplar in this case) and their effects on pyrolysis-oil compositions.

Keywords: Analytical fast pyrolysis; C, Holocellulose; CAD, CINNAMYL ALCOHOL DEHYDROGENASE; CCoAOMT, CAFFEOYL-CoA O-METHYLTRANSFERASE; COMT, CAFFEIC ACID O-METHYLTRANSFERASE; G, Guaiacyl units; GC, Gas chromatography; Genetically modified poplar; H, p-hydroxyphenyl units; L, Lignin-derived aromatic compounds; L-G, Guaiacyl lignin-derived compounds; L-H, p-Hydroxyphenyl lignin-derived compounds; L-S, Syringyl lignin-derived compounds; Lignin; MD, Mahalanobis distance; MS, Mass spectroscopy; PC, Principal component; Phenolic compounds; Principal component analysis; Py, Micropyrolysis or micropyrolyzer; S, Syringyl units; as, Antisense line; s, Sense line.