Abstract
The sustainability and economic feasibility of modern biorefinery depend on the efficient processing of both carbohydrate and lignin fractions for value-added products. By mimicking the biomass degradation process in white-rote fungi, a tailored two-step fractionation process was developed to maximize the sugar release from switchgrass biomass and to optimize the lignin processability for bioconversion. Biomimicking biomass processing using Formic Acid: Fenton: Organosolv (F2O) and achieved high processability for both carbohydrate and lignin. Specifically, switchgrass pretreated by the F2O process had 99.6% of the theoretical yield for glucose release. The fractionated lignin was also readily processable by fermentation via Rhodococcus opacus PD630 with a lipid yield of 1.16 g/L. Scanning electron microscope analysis confirmed the fragmentation of switchgrass fiber and the cell wall deconstruction by the F2O process. 2D-HSQC NMR further revealed the cleavage of aryl ether linkages (β-O-4) in lignin components. These results revealed the mechanisms for efficient sugar release and lignin bioconversion. The F2O process demonstrated effective mimicking of natural biomass utilization system and paved a new path for improving the lignin and carbohydrate processability in next generation lignocellulosic biorefinery.
Highlights
The demands for renewable energy have become urgent in recent years due to the increases in greenhouse gas emissions and various other environmental concerns associated with fossil fuel consumption (Himmel et al, 2007)
When the switchgrass was treated with formic acid and dioxane, the hemicellulose content reduced to about 6.38%, indicating that the hemicellulose was almost removed from switchgrass biomass (Figure 1A)
By mimicking the natural lignocellulosic biomass degradation of white-rot fungi, the present study developed a two-step organosolv pretreatment (F2O) to achieve high processability of both carbohydrates and lignin
Summary
The demands for renewable energy have become urgent in recent years due to the increases in greenhouse gas emissions and various other environmental concerns associated with fossil fuel consumption (Himmel et al, 2007). Perennial feedstock, such as switchgrass, could provide environmental and economic advantages over the current corn-based ethanol, considering the higher net energy gain and the fact that it requires only marginal land use (Yuan et al, 2011) Despite the potential it presents, lignocellulosic biomass conversion is a more challenging process due to the recalcitrant nature of biomass and the need to disrupt secondary cell wall structure to release carbohydrate and lignin (Isikgor and Becer, 2015; Balch et al, 2017). The Formic Acid: Fenton: Organosolv (F2O) pretreatment process developed in this study could overcome the traditional refinery challenges of low fermentable sugar yield and inefficient lignin utilization. This study could open new avenues for biorefinery design towards the co-utilization of carbohydrate and lignin processibility
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