Abstract
BackgroundMiscanthus is a leading bioenergy crop with enormous lignocellulose production potential for biofuels and chemicals. However, lignocellulose recalcitrance leads to biomass process difficulty for an efficient bioethanol production. Hence, it becomes essential to identify the integrative impact of lignocellulose recalcitrant factors on cellulose accessibility for biomass enzymatic hydrolysis. In this study, we analyzed four typical pairs of Miscanthus accessions that showed distinct cell wall compositions and sorted out three major factors that affected biomass saccharification for maximum bioethanol production.ResultsAmong the three optimal (i.e., liquid hot water, H2SO4 and NaOH) pretreatments performed, mild alkali pretreatment (4% NaOH at 50 °C) led to almost complete biomass saccharification when 1% Tween-80 was co-supplied into enzymatic hydrolysis in the desirable Miscanthus accessions. Consequently, the highest bioethanol yields were obtained at 19% (% dry matter) from yeast fermentation, with much higher sugar–ethanol conversion rates by 94–98%, compared to the other Miscanthus species subjected to stronger pretreatments as reported in previous studies. By comparison, three optimized pretreatments distinctively extracted wall polymers and specifically altered polymer features and inter-linkage styles, but the alkali pretreatment caused much increased biomass porosity than that of the other pretreatments. Based on integrative analyses, excellent equations were generated to precisely estimate hexoses and ethanol yields under various pretreatments and a hypothetical model was proposed to outline an integrative impact on biomass saccharification and bioethanol production subjective to a predominate factor (CR stain) of biomass porosity and four additional minor factors (DY stain, cellulose DP, hemicellulose X/A, lignin G-monomer).ConclusionUsing four pairs of Miscanthus samples with distinct cell wall composition and varied biomass saccharification, this study has determined three main factors of lignocellulose recalcitrance that could be significantly reduced for much-increased biomass porosity upon optimal pretreatments. It has also established a novel standard that should be applicable to judge any types of biomass process technology for high biofuel production in distinct lignocellulose substrates. Hence, this study provides a potential strategy for precise genetic modification of lignocellulose in all bioenergy crops.
Highlights
Miscanthus is a leading bioenergy crop with enormous lignocellulose production potential for biofuels and chemicals
Pair IV samples did not show significantly different cell wall compositions at P > 0.05, suggesting that this pair of samples should be powerful to explore how biomass enzymatic hydrolysis is affected by wall polymer features and interlink styles
Despite that cellulose crystalline index (CrI) of raw materials has been well examined as the negative factor on biomass enzymatic saccharification [3, 7, 9, 36], this study indicated that the CrI of three optimal pretreated biomass residues did not show significant correlation with biomass enzymatic hydrolysis, probably due to the distinct hemicellulose and lignin extractions and specialized polymer feature alterations from the optimal pretreatments as described above (Figs. 5 and 7)
Summary
Miscanthus is a leading bioenergy crop with enormous lignocellulose production potential for biofuels and chemicals. It becomes essential to identify the integrative impact of lignocellulose recalcitrant factors on cellulose accessibility for biomass enzymatic hydrolysis. We analyzed four typical pairs of Miscanthus accessions that showed distinct cell wall compositions and sorted out three major factors that affected biomass saccharification for maximum bioethanol production. Cellulosic ethanol production involves three major steps: initial physical and chemical pretreatment to deconstruct plant cell walls, sequential enzymatic hydrolysis to release soluble sugars, and final yeast fermentation to produce bioethanol [3, 4]. Cellulose is the major wall polymer of all lignocelluloses, but its crystallinity and degree of polymerization (DP) have been characterized as one of the factors negatively affecting biomass enzymatic saccharification under various physical and chemical pretreatments [3, 7]. As biomass porosity has multiple parameters measured from different assays such as Simons’ stain [11, 14], Congo red [15], and nitrogen adsorptions [3], it remains yet to be identified the crucial parameter(s) precisely accounting for biomass saccharification and bioethanol production
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
