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Screening of Microbial Pretreatment Process on Corn Stalk

Author: JiangJie
Tutor: ChenHong；WangDingYong
School: Southwestern University
Course: Environmental Engineering
Keywords: corn stalk white rot fungi lignin hemicellulose cellulose
CLC: S141.4
Type: Master's thesis
Year: 2010
Downloads: 290
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Abstract

The yield of crop straw is about 2 billion tons per year all around the world. Among them, there are about 600～700 million tons in China. Reasonable utilization of the straws is beneficial to the development of agriculture and rural areas, or it can take many negative effects. Traditional method to disposal straws is incineration which can realize the quantitative reduction of the straws to a great extem But it is a waste of resource though reducing quantity of staws to a great extent. Meanwhile, the crop straw burning can produce a lot of CO, CO2, NOx, which would cause serious air pollution. What’s more, the high temperature form burning has a killing effect on the soil microorganism, going against the growth of them. Finally, it would cause soil hardening and decline of soil fertility. The land desertification is one of the most serious eco-environmental problems. Although more attention is paid to controlling and modifying the sandy soil resent years, it is still in a stalemate phase. The sandy soil controlled by using straws starts about 90th last century in China. The initial stage with using straws as sand control hedgesand or covering is just as abroad. But it was just a limited auxiliary measure, because it can not solve problems radically.Judging form the structure and properties of the straw, it is especially important to return after a pretreatment if adopting straw as a basic material to control the sandy soil. Corn straw is uneasy to be decomposed in the nature world because of containing a great deal of crude fiber, like lignin, cellulose' dissertation">hemicelluloses and cellulose. Therefore, it is significant for decomposing the straw effectively and quickly, releasing the effective elements sufficiently to do the pretreatment, which can destroy all kinds of covalent between the structural unit and degrade lignin and cellulose. The purpose of this paper is to select the best pretreatment process on corn straw by analyzing the degradation of lignin, hemicelluloses and cellulose under different treatments and the release condition of the nutrition.in order to provide badic data for the material preparatin of sandy soil improvement.The results were all as follows:1.The lignin hemicelluloses and cellulose can be well degraded will only whitc rot fungi for com straw of large particle(1-3cm、4-5cm).while the dcgradation would be inhibited with cellilose-decomposing microorganisms.The degradation of hemicellilose and cellulose wil be increased .if cellulose-decompoaing microorganisms is inoculraed at a proper time after white rot fungi inoculated.compared with subculturing white rot fungi alone of the small particle sixe(0.5cm).but the degradation of lignin is higher with white rot fungi subculturing alone.2.The result is that lignin.hemicelluloses and cellulose of the large particle can be degraded at gretler degree with white rot fungi subculturing .The degradation dfftciency of 4-5cm is the best while subculturing white rot fungi alone for 30-40 days.The content of lignin decreases from 13.4％to 6.0％,and the degradation gets 55.5％,which is 12.7％and 3.0％higher than those of 0.5cm and 1-3cm.Thecontent of hemicelluloses dcrdases from 36％to 14％.and the degradation gets 61.0％,which is 27.1％and 15.1％higher than those of 0.5cm and 1-3cm.The content of cellulose decrease；from 48.5％to 20.1％.and the degradation gets 58.5％,which is 13.0％and 4.6％higher than those of O.5cm and 1-3cm.3.The process of microbial degradation of the com straw is the process of incessant decomposition of the organic matter.The degradation effciency of 4-5cm is the best while subculturing white rot fungi alone for 45 days.The content of organic decreases from 796.2g/kg to 558.3g/kg,and the degradation gets 29.9％.4.The humus concentration of the corn straw has a significantly negative correlation with the lignin concentration.The smaller the particle size is,the greater the correlation is.The content of 4-5cm is the best while subculturing white rot fungi alone for 40 days.The content of the humus increases from 23.2％to 41.0％,and the growth rate gets 55.5％,which is 8.0％and 5.0％higher tham those of 0.5cm and 1-3cm.5.The average growth rate of the total nitrogen and the total phosphorus of 4-5cm gets 100.2％and 157.2％,with white rot fungi subculturing alone for 30～40 days.The average growth rate of the available nitrogen and the available phosphorus of 0.5cm gets 269.6％and 83.8％,with white rot fungi subculturing alone for 30～40 days.The average growth rate of the total potassium of 4-5cm gets 57.2％,with cellulose-decomposing microorganisms subculturing 15～25days after white rot fungi inoculation 15 days.The average growth rate of the available potassium of 4-5cm gets 39.7％,with cellulose-decomposing microorganisms subculturing 1O～20 days after white rot fungi inoculation 20 days. Geting across the testing results and considering about time, economy and some other factors in reality, the best pretreatment process of the corn straw is:subculture white rot fungi alone for 25～30 days on the particle of 4-5cm.

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