| The lignocellulose is the most abundant carbohydrate compounds in the world. Lignocellulose-based biofuels have been regarded as a clean, safe and sustainable energy, it has been considered as a major renewable biomass source for biofuels. It is sound for any research on the production of biofuels from biomass as it is important to the development of economy and society. The sea island cotton (G barbadense) and Upland cotton (G hirsutum), Jute(Corchorus capsularis L), Kenaf(Hibiscus cannabinus L) and Ramie (Boehmeria nivea L. Gaud) are all the important fiber crops well planted all over the world with vast growth acreage and high fiber yield. In this study, the stalks of two cotton species, and three major fiber crops were pretreated with steam explosion followed by acid (H2SO4) or alkali (NaOH) at various concentrations treatment as pretreatment and the sequential biomass enzymatic saccharification efficiency were compared in between the species and the pretreatment. In addition, the yeast fermentation inhibition from various pretreatments was also evaluated in order to find out an optimal biomass process for those crops stalk. Furthermore, the cell wall structure of polymer features was detected under scanning electron microscope to analysis of the pretreatment affection. The multiple linear regression (MLR) and stepwise multiple regression (SLR) were used to build a QSAR (quantitative structure-activity relationship) model based on degradation efficiency, cell wall component content and fine structure of the cell wall as key factors. The model has widely prediction ability for those fiber plants their stalk is character between herbaceous plant and woody plant. It provides a theoretical basis for biomass energy plant selection. Here are the main points proposed in this study:(1) Steam explosion has large enhancements on biomass digestibility by largely reducing DP (degree of polymerization) of cellulose, and extracting hemicellulose and lignin in both cotton stalks and fiber crops stem.(2) Steam explosion with dilute acids (0.25%) causes not only the relative higher biomass digestion, higher sugar-ethanol conversion rates, and lower inhibitor releasing in cotton stalks. The two-step pretreatment should be the optimum option in fiber crops stalk as steam explosion and followed 1.00% H2SO4/NaOH treatment.(3) Pretreatment of extremely high concentration alkali (16.00% NaOH) with raw stalks resulted in the highest hexoses yields, but also led to the lowest sugar-ethanol conversion rates in both cotton stalks and fiber crops.(4) The cellulose polymerization degree (DP), crystalinity, and arabinose substitution degree of xylans (reverse Xyl/Ara) were the major factors on biomass digestibility in both cotton stalks and fiber crops.(5) Correlation analysis between contents of S monomer and xylan suggested S monomer might play an important role in the forming of lignin-hemicellulose compounds in those five fiber crops.(6) Comparison among various pretreatments, which applied in each species, revealed that G barbadense (Island cotton, Gb) and Jute (Corchorus capsularis L) showed highest biomass digestion in cotton stalks, and fiber crops, respectively. |
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