| Nowadays, renewable energy has become a more and more important part of the future energy pattern and a strategic choice for almost every country when the energy shortage and environmental pollution have begun to influence the people’s livelihood. Among all kinds of renewable energy, the2th generation of bioethanol technology using lignocellulose as raw material has drawn a lot of people’s attention. Lignocellulose coming from aquatic or terrestrial plant varies a lot in chemical composition and structural characteristics, which may be very important for the the sugar production and efficiency of enzymatic hydrolysis. In this paper, Eichhornia crassipes (E. crassipes) and Sugarcane bagasse were selected as the representatives of the aquatic and terrestrial plant respectively, the differences of chemical composition and structural characteristics of cellulose were analysed, the cellulose of the plants were extracted, and their artifical biomass with different ratio of cellulose, hemicellulose and lignin, as known as "the three components", were formulated their extracted cellulose. Based on the sugar production which experiment by enzymatic hydrolysis of the artificial biomass, a linar correlation equation of reducing sugar production and three components’ratio was established, the comparison between theoretical sugar production estimated by correlation equation and sugar production of natural biomass were conducted, the reasons that caused difference in theoretical sugar productions of2kinds of artificial biomass, and the difference between theoretical sugar productions of artificial biomass and those of natural biomass were analysed. The research provided theoretical foundation for the selection of lignocellulose materials with different living sources. As for E. crassipes, we studied the influence of different combination rates of the plant in different growth periods in the efficiency of enzymatic hydrolysis and the sugar production. In addition, the three components isolation method from E. crassipes and Sugarcane bagasse was discussed. Main results are listed as below:(1) The contents of wild E. Crassipes is cellulose, hemicellulose, lignin, and crude ash, which are19.44%,41.51%,11.66%, and16.25%, respectively. As for Sugarcane bagasse, the contents are32.38%,28.65%,13.38%, and13.58%correspondingly. The wild E. crassipes and Sugarcane bagasse have almost the same total content of cellulose and hemicellulose. (2) Using nitric acid and anhydrous ethanol (volume ratio1:4) as extracting solution, cellulose in both E. crassipes and sugarcane bagasse could be extracted completely in the conditions of1:25solid-liquid and boiling water-bath heating for60mins. Between two sources, the purity of cellulose from sugarcane bagasse was higher. In Fans method for three components determination, after acid detergent solution treatment of the lignocellulose, precipitation of the obtained liquid samples by ethanol addition also couldn’t separate hemicellulose very well. Meanwhile, acid-detergent-lignin step couldn’t separate lignin very well.(3) Along with the growth of E. crassipes, the contents of cellulose and hemicellulose increased in the early stage, but decreased slightly in the late stage. In contrast, the content of lignin was relatively constant. In the same enzymatic hydrolysis condition and without pre-treatment, the sugar yield of the seedling sample was significantly higher than those of the samples with3or7weeks’ cultivation. With the extension of cultivation period, the cellulose crystallinity index (CrI) increased, and the samples of3or7weeks’cultivation had higher affinity between the three components than did seedling sample, which might be the crucial reason why seedlings had higher efficiency of sugar production. Thus, the best harvest time (growth period) need to be took into account different factors, the biomass amount, the contents of three components, and the sugar yield rate/sugar conversion rate, should be considered comprehensively for the efficient usage of E. crassipes.(4) Based on the enzymatic hydrolysis experiments of artificial biomass with different ratios of the three components in which cellulose are extracted from E. crassipes and sugarcane bagasse, the equation y=/β1χ1+β2χ2could illustrate the different contribution of cellulose and hemicellulose for the reducing sugar production well enough. Here y represented the yield of reducing sugar, χ1and χ2represented the content of cellulose and hemicellulose, respectively. It can be seen that hemicelluloses in two kinds of artificial biomass both exhibit bigger contribution for reducing sugar production than celluloses, namely, β2>β1. Moreover, the cellulose from E. crassipes had more contribution for reducing sugar production than that from the Sugarcane bagasse, which may be due to the lower CrI of E. crassipes biomass.(5) The enzymatic hydrolysis sugar productions of two kinds of natural biomass with no pretreatment were both significantly lower than those of their artificial biomass, i.e., theoretical sugar production. However, the sugar productions of two kinds of extracted cellulose, and the biomass pretreated by1%H2O2+2%NaOH of these two plant materials, were close to those of their artificial biomass. The difference in sugar production between natural or pretreated biomass and artificial biomass indicated the extent of combination of three components in natural biomass that would hinder the hydrolysis. Meanwhile, with or without pretreatment, or the intensity of pretreatment, or the extent of lignin and ash removal would directly affect this difference, indicating the necessity and importance of pretreatment. |
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