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Biotechnol Biofuels. 2019 Apr 27;12:99. doi: 10.1186/s13068-019-1437-4. eCollection 2019.

A finalized determinant for complete lignocellulose enzymatic saccharification potential to maximize bioethanol production in bioenergy Miscanthus.

Alam A1,2, Zhang R1,2, Liu P1,2, Huang J1,2, Wang Y1,2, Hu Z1,2, Madadi M1,2, Sun D1,3, Hu R4, Ragauskas AJ5, Tu Y1,2, Peng L1,2.

Author information

1
1Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan, 430070 China.
2
2College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070 China.
3
3School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan, 430068 China.
4
4College of Food Science and Technology, Hubei University of Arts and Science, Xiangyang, 441053 China.
5
5Department of Chemical and Biomolecular Engineering, University of Tennessee-Knoxville, Knoxville, TN 37996-2200 USA.

Abstract

Background:

Miscanthus 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.

Results:

Among 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).

Conclusion:

Using 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.

KEYWORDS:

Bioethanol yield; Biomass porosity; Biomass saccharification; Miscanthus; Polymer features; Polymer linkages

Conflict of interest statement

The authors declare that they have no competing interests.

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