MOESM1 of Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar

Additional file 1. Table S1. Sugar yields obtained from different pretreatment strategies. Table S2. Percent mass loss obtained after different pretreatments. Figure S1. Water retention value (WRV) for untreated biomass and alkaline pre-extracted biomass. Figure S2. Enzymatic hydrolysis inhibition studies using Avicel as a substrate. Figure S3. Partial 2D HSQC NMR spectra of (A) lignin from untreated, debarked whole poplar, (B) solubilized lignin from reference case Cu-AHP pretreated poplar, and (C) solubilized lignin from modified Cu-AHP pretreated poplar

Additional file 1: of Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Figure S1. EELS spectrum of the Cu-containing nanoparticles showing the Cu L2,3 edge providing evidence that the Cu in these particles is primarily in the Cu(I) oxidation state with contributions by Cu(0). Figure S2. Partial 2D HSQC NMR spectra of (a) whole cell wall untreated poplar, (b) solubilized lignin, and (b) residual poplar cell walls following Cu-catalyzed AHP pretreatment. Contours are colored to match the structures for aromatic components. [This is the same as Fig. 6 in the main paper except that important polysaccharide correlations have been assigned]

Lignin Conversion to Low-Molecular-Weight Aromatics via an Aerobic Oxidation-Hydrolysis Sequence: Comparison of Different Lignin Sources

Diverse lignin samples have been subjected to a catalytic aerobic oxidation process, followed by formic-acid-induced hydrolytic depolymerization. The yield of monomeric aromatic compounds varies depending on the lignin plant source and pretreatment method. The best results are obtained from poplar lignin isolated via a acidolysis pretreatment method, which gives 42 wt% yield of low-molecular-weight aromatics. Use of other pretreatment methods and/or use of maple and maize lignins afford yields of aromatics ranging from 3 to 31 wt%. These results establish useful references for the development of improved oxidation/depolymerization protocols

Engineered Lignin in Poplar Biomass Facilitates Cu-Catalyzed Alkaline-Oxidative Pretreatment

Both untransformed poplar and genetically modified “zip-lignin” poplar, in which additional ester bonds were introduced into the lignin backbone, were subjected to mild alkaline and copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment. Our hypothesis was that the lignin in zip-lignin poplar would be removed more easily than lignin in untransformed poplar during this alkaline pretreatment, resulting in higher sugar yields following enzymatic hydrolysis. We observed improved glucose and xylose hydrolysis yields for zip-lignin poplar compared to untransformed poplar following both alkaline-only pretreatment (56% glucose yield for untransformed poplar compared to 67% for zip-lignin poplar) and Cu-AHP pretreatment (77% glucose yield for untransformed poplar compared to 85% for zip-lignin poplar). Compositional analysis, glycome profiling, and microscopy all supported the notion that the ester linkages increase delignification and improve sugar yields. Essentially no differences were noted in the molecular weight distributions of solubilized lignins between the zip-lignin poplar and the control line. Significantly, when zip-lignin poplar was utilized as the feedstock, hydrogen peroxide, catalyst, and enzyme loadings could all be substantially reduced while maintaining high sugar yields