Preliminary Study On The Effects Of Different Pretreatment Methods On The Enzymatic Digestibility Of The Cellulose Of Eupatorium Adenophorum And Chromolaena Odorata

Eupatorium adenophorum and Chromolaena odorata are two noxious invasive weeds, which widely spread in tropics and subtropics worldwide. They affect badly the productions of agriculture, forestry and stockbreeding in introduced range. They also influence growth of native species, threatening biodiversity security, deteriorating ecological environments. There are not feasibly effective methods to control the two weeds so far. It is may be a good method for controlling these weeds to develop effective methods to use them. The possibility to use the two species as feedstock to produce biofuel, such as ethanol, was evaluated primarily in this thesis. We focused on the effects of different pretreatment processes of the stems of the weeds on the production of fermentable sugars.Firstly, the contents of some components in stems and leaves of the two weeds were determined by the Component Analysis Method of Non-wood raw material for paper making. The contents of cellulose, holocellulose and Klason lignin in stems of E. denophorum / C. odorata were 37.14 %/37.72 %, 66.22 %/71.55 %, 16.42 %/20.74 %, respectively, similar to those of cornstalk and wheat straw. Thus, it is possible to use the stems of E. adenophorum and C. odorata as cellulosic biomass feedstock to produce biofuel.Secondly, the effects of different pretreatment methods on the enzymatic digestibility of the two weeds were studied. High yield of reducing sugar was obtained through pretreatment of the stems of the two species with dilute H2SO4, which can hydrolyze hemicellulose. 32.89 % reducing sugar was obtained when E. adenophorum was treated at the optimum conditions with H₂SO₄: liquid/solid ratio of 8:1, 1 % H2SO4 at 120℃for 120 min, and 25.96 % reducing sugar was obtained with C. odorata under the same optimal condition: liquid/solid ratio of 8:1, 2 % H2SO4 at 120℃for 150 min. NaOH pretreatment increased the quality of the product for cellulase treatment through removing lignin. The conversion ratio of cellulose after 72 hours'enzymatic hydrolysis was 18.5 % and 10 % for E. adenophorum and C. odorata, respectively, when pretreated at the optimum condition: liquid/solid ratio of 6:1, 10 % NaOH at 110℃for 120 min. Compared with NaOH pretreatment, peracetic acid (PAA) pretreatment can remove lignin of the weeds more effectively, increasing the conversion ratio of cellulose. The optimum conditions of PAA pretreatment were liquid/solid ratio of 4:1, 40 % PAA at 90℃for 90 min and liquid/solid ratio of 5:1, 50 % PAA at 90℃for 60 min for E. adenophorum and C. odorata, respectively. At these conditions, conversion ratios of cellulose after 72 hours'enzymatic hydrolysis were 38 % and 28 % for E. adenophorum and C. odorata, respectively.Therefore, based on the characteristics of fast growth, wide distribution and large-harvested biomass, the two weeds may be used as potential feedstock to produce ethanol. This would be significant for the improvement of the ecological environments and the sustainable development in the invaded area.