| Eucommia ulmoides Oliver(EU) is an elm-like deciduous and dioecious tree belonging to only one species, one genus(Eucommia) and one family(Eucommiaceae) in China. As recorded in the traditional Chinese medicine(TCM), the bark, cortex Eucommiae, together with its leaf, folium Eucommiae, have been listed in “China Pharmacopoeia” with the pharmacological functions of “nourishing liver and kidney, strengthening muscles and bones, and soothing the fetus”. As one of the most valuable precursor in advanced polymer materials, guttapercha, it is highly necessary to increase the extractability and broaden its value-added application because of the limited availability of bioresources and high extracting cost. Moreover, other useful components, such as extractum and polysaccharides, should be also isolated during the whole process to increase the economic feasibility of this valuable resource. The first question is how to isolate the usefull components from EU via “unaltered form”. Another question is how to select and develop more precise method to analysis the chemical structures of the components of EU. With the development of “biorefinery”, more questions regarding of EU should be illuminated, such as the dissociative mechanism of the components of EU during pretreatment. The solutions to the above-mentioned questions will not only promote the development of biochemistry, but also provide some theoretical foundations to the value-added applications of the EU. In this doctoral thesis, some aspects regarding to the relationship between the primary metabolites(photosynthesic characteristics) and secondary metabolites(chemical compositions) of the different EU planting model was firstly presented. Based on the isolation and analytical methods presented, the fundamental chemistry of EU and chemical transformations of EU during different leading pretreatments will be also investigated. In addition, based on the results obtained, some feasible methods for disassembling the EU into main components will be presented in a biorefinery scenario.The dynamic changes of photosynthesic characteristics, chemical compositions and cumulative production between the traditional arbor forest model of Eucommia planting(AFMEP) and using leaf model of Eucommia planting(ULMEP) were systematically investigated. Results showed that the light-saturated net photosynthetic rate in ULMEP was significantly higher than that in AFMEP. The content of lignin in AFMEP wood was higher than that of ULMEP wood, while the amounts of β-O-4 linkages were abundunt in lignin from ULMEP wood, which was beneficial to utilize the ULMEP wood. By contrast, the content of carbohydrates in this wood present an opposite trend. Besides, the contents of different secondary metabolites in the leaves from AFMEP and ULMEP varied with the seasonal change. Moreover, the cumulative production of dry biomasses in wood, leaves and barks of EU at the same periods(10 years) were all significantly higher in ULMEP than those in AFMEP.Barks and leaves of EU were successively fractionated by a multi-step treatment process. The extractum and water-soluble polysaccharides, alkali-extractable polysaccharides, and guttapercha, were sequentially obtained by hot-water extraction, alkaline treatment, and extended enzymatic hydrolysis, respectively. Results showed that the primary bioactive components of extractum from leaves were mainly consisted of chlorogenic acid, quercetin, geniposide and aucubin, and those from barks were consisted of geniposidic acid, geniposide and aucubin. In addition, the water-soluble polysaccharides from barks and leaves were mainly composed with glucose, whereas, the alkali-extractable polysaccharides from the barks and leaves were primarily the arabinose. Emphatically, the guttapercha fractions obtained from barks exhibited higher molecular weights with narrow polydispersity as compared to those from leaves. The data presented indicated that the multi-step process is an environmentally benign and advantageous scheme for value-added and potential industrial application of EU resources.EU wood was successively treated by autohydrolysis and organosolv pretreatment integrated process. Autohydrolysis pretreatment facilitated xylooligosaccharides production, subsequent organosolv pretreatment to obtain high-purity lignin and digestible cellulose-rich residue. Results showed thatthelignin fractions obtained exhibited smaller molecular weights, narrow polydispersity,more phenolic OH groups and higher syringyl/guaiacyl ratios(S/G) than the milled wood lignin. NMR characterization of the lignin revealed that the β-O-4 linkages significantly cleaved and the structure of stilbene formed, but its resinol(β-β) was resistant to be degraded by organosolv delignification. Moreover, the glucose yield of the integrated residue achieved a maximum value of 89.3% after enzyme hydrolysis, separately about 1.0, 1.3, 3.8 times as compared to that of the ethanol organosolv residue, the hydrothermally treated residue and the EU wood, respectively, which indicated that the integrated process was a promising approach to value-added utilization of the EU wood.EU wood was successively treated by a combined system based on steam explosion pretreatment(SEP) and alkaline hydrogen peroxide post-treatment(AHPP). In this case, SEP was to disrupt the lignocellulosic structure, and the subsequent AHPP process was to isolate the high-purity lignin and cellulose-rich substrates. Results showed that the lignin fractions obtained during the AHPP exhibited smaller molecular weights, narrow polydispersity, less phenolic OH groups and lower syringyl/guaiacyl ratios(S/G) than those of the milled wood lignin(SEMWL) obtained from the only steam exploded EU. NMR characterization of lignin revealed that the AHPP process has a slight effect on the composition and molecular characteristic of lignin, and the lignin isolated had lower amounts of substructures(aryl-β-ether, resinol, and phenylcoumaran linkages) as compared to those in SEMWL. Moreover, the subsequent SEP followed by AHPP process enhanced the enzymatic hydrolysis of celluloserich substrates to a maximum value of 91.69%. It was found that the synergistic treatment removed most of lignin, degraded hemicelluloses, and incurred a higher crystalline index and surface area of the cellulose-rich substrates as compared to the only steam explosion pretreatment. The combination of the SEP and AHPP processes is an environmentally benign and advantageous scheme for the production of high-purity lignin and cellulose-rich substrates, which will be further transformed into the value-added biomaterials and bioethanol.EU wood was consecutively treated by autohydrolysis pretreatment and chemical carbonization post-treatment based on a biorefinery process. The autohydrolysis pretreatment under different conditions recovered different yields of xylooligosaccharides(XOS, 1.5%-34.4%) and others degraded products from hemicelluloses, and the subsequent carbonization of the pretreated substrates produced the high-performance activated carbon and a small amount of flue gas. Results showed that the optimal condition of the autohydrolysis pretreatment(170 °C for 1 h) and followed carbonization process(50% H3PO4, 550 °C, 120 min) yielded 10.37 kg XOS, 1.39 kg degraded hemicellulosic products, 17.29 kg others products from hemicelluloses and 40.72 kg activated carbon(SBET of 1534.06 m2/g) form the 100 kg raw materials, in which the surface area of AC170-1.0 was highest among all the activated carbon samples. Simultaneously, 29.14 kg gas products generated from the optimum integrated process was significantly lower than that from the direct carbonization process(68.84 kg). Besides, the optimal activated carbon(AC170-1.0) also showed a moderate catalytic activity and high stability for hydrogen production by catalytic methane decomposition. Overall, the data presented indicated that the integrated process is an eco-friendly and advantageous process to produce XOS and activated carbon, which is beneficial for value-added and industrial application of EU wood. |
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