Abstract
Plant lignin is one of the major wall components that greatly contribute to biomass recalcitrance for biofuel production. In this study, total 79 representative Miscanthus germplasms were determined with wide biomass digestibility and diverse monolignol composition. Integrative analyses indicated that three major monolignols (S, G, H) and S/G ratio could account for lignin negative influence on biomass digestibility upon NaOH and H2SO4 pretreatments. Notably, the biomass enzymatic digestions were predominately affected by the non-KOH-extractable lignin and interlinked-phenolics, other than the KOH-extractable ones that cover 80% of total lignin. Furthermore, a positive correlation was found between the monolignols and phenolics at p<0.05 level in the non-KOH-extractable only, suggesting their tight association to form the minor wall-networks against cellulases accessibility. The results indicated that the non-KOH-extractable lignin-complex should be the target either for cost-effective biomass pretreatments or for relatively simply genetic modification of plant cell walls in Miscanthus.
Highlights
Lignocellulose is the most abundant and sustainable biomass on the earth for biofuels and other chemical products [1,2,3]
The genetic modification of plant cell walls is considered a promising solution in bioenergy crops and it has become essential in understanding the effects of wall polymer on biomass digestibility [10,11,12]
Total 79 representative Miscanthus samples have been determined with a variation of lignocellulose enzymatic digestibility and a diversity of three monolignols (S, G, H) and seven interlinkedphenolics compositions
Summary
Lignocellulose is the most abundant and sustainable biomass on the earth for biofuels and other chemical products [1,2,3]. The current biomass process mainly involves three major steps, namely, physical and chemical pretreatment for plant cell wall destruction, enzymatic hydrolysis for saccharification, as well as yeast fermentation for ethanol production [4]. Plant cell walls are mainly composed of cellulose, hemicelluloses, and lignin with relatively small amounts of pectin and proteins [13,14]. Lignin is an amorphous polymer with phenylpropane units, which mostly comprise three monomers, namely, p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) [17]. These monomers are linked by ether-, ester- and C-C bonds that are irregularly repeated [18,19]. Despite that the lignin level and the S/G ratio show the negative effects on biomass saccharification in transgenic switchgrass [22,23], the higher S/G ratio in natural populus was recently reported to exhibit a positive effect on sugar release while the negative effect of lignin level is less pronounced [20]
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