不同种类表面活性剂联合离子液体预处理稻秆的物化特性研究

预处理是提高木质纤维材料酶解效果的关键步骤,更是木质纤维材料制造生物乙醇的重要环节.因此,对木质纤维材料进行预处理以促进酶解糖化过程具有重要意义.本研究以稻秆为原料,探讨不同类型表面活性剂(包括阳离子型、阴离子型、非离子型、生物)联合离子液体对木质纤维材料转化率及酶解初速度的影响,并通过稻秆成分分析、FTIR、XRD对处理前后稻秆的结构、结晶性进行了分析比较.结果表明,与单独离子液体处理相比,表面活性剂联合离子液体预处理稻秆可提升纤维转化率,效果为:生物表面活性剂-离子液体非离子型表面活性剂-离子液体阴离子型表面活性剂-离子液体阳离子型表面活性剂-离子液体.与未处理及单独离子液体处理稻秆相比,生物表面活性剂-离子液体预处理稻秆的纤维转化率分别提高55.38%和22.03%.     

超声波辅助离子液体-盐酸溶液预处理稻秆的研究

为研究超声波对离子液体-盐酸溶液预处理木质纤维素的影响,采用氯化-1-丁基-3-甲基咪唑和氯化-1-烯丙基-3-甲基咪唑的盐酸溶液在超声辅助下对稻秆于30~70℃进行预处理,探讨了温度、酸度和处理时间对酶解产糖量的影响,并在最佳条件下通过酶解糖化、成分分析、表面形貌、结晶度及化学结构的变化对有无超声辅助下预处理的效果进行考察.结果表明,温度、酸度及处理时间对酶解产糖量具有显著影响,在超声波辅助下,产糖量、纤维转化率及脱木质素率分别提高20.13%~28.96%、31.69%~35.23%和18.06%~19.33%.扫描电镜、X-射线衍射及傅里叶变换红外光谱分析表明,超声波辅助离子液体-盐酸溶液预处理能够促进对稻秆表面形貌和化学结构的破坏,并降低纤维素的结晶度.     

不同反胶束体系萃取纤维素酶的条件优化对比研究

采用3种不同的表面活性剂双(2-乙基己基)磺基琥珀酸钠AOT、十六烷基三甲基溴化铵CTAB及鼠李糖脂RL)溶于正己醇/异辛烷相构建不同的反胶束体系,并对比研究了不同反胶束体系萃取纤维素酶的优化条件.分别探讨了水相pH值、表面活性剂浓度、离子强度和离子种类对纤维素酶萃取效率的影响.实验结果如下:在实验条件下,AOT、CTAB和RL 3种反胶束体系水相最佳pH值分别为3.0、8.0和3.0;表面活性剂最佳浓度依次为:AOT 23.7mmol/L、CTAB 15mmol/L和RL 2.75mmol/L;水相中NaCl浓度会影响纤维素酶的萃取率,3种表面活性剂构建的反胶束体系萃取纤维素酶的萃取率均随着盐离子浓度的增大而降低;水相中离子种类也会影响纤维素酶的萃取率.比较不同反胶束体系在最佳条件下萃取纤维素酶的最佳萃取率:CTAB>AOT>RL.     

表面活性剂强化超声波-离子液体预处理对水葫芦酶解的影响

为探讨表面活性剂对超声波-离子液体(US-IL)预处理木质纤维素的影响,本试验采用十二烷基硫酸钠(SDS)强化US-IL对水葫芦进行预处理,通过酶解、组成成分、表面形貌、结晶度以及化学结构的变化对预处理效果进行考察.结果显示,与未添加SDS相比,超声波-离子液体-十二烷基硫酸钠(US-IL-SDS)预处理能够有效降低纤维素的结晶度并去除木质素,酶解还原糖产量、纤维转化率及其脱木率分别提高72.23%、58.74%及21.01%.并且,SEM、XRD以及FTIR结果也表明SDS能够促进US-IL对水葫芦结构的破坏.因此,将SDS运用于辅助US-IL预处理木质纤维素具有一定可行性和良好的运用前景.     

鼠李糖脂逆胶束体系中纤维素酶的后萃研究

采用生物表面活性剂鼠李糖脂(rhamnolipid,RL)构建RL/异辛烷/正己醇的逆胶束体系,并研究了该体系中纤维素酶后萃过程的影响因素.分别考察了后萃水相pH值、振荡时间、离子种类和强度以及添加短链醇对纤维素酶的后萃率和酶活回收率的影响.结果表明,后萃水相最佳pH值为7.0,振荡时间以30 min为最佳,后萃水相中离子强度以0.15 mol·L-1KCl最佳,正丁醇的最佳添加量为2%.在最佳实验条件下,纤维素酶的后萃率和酶活回收率分别可以达到76.22%和93.39%.生物表面活性剂RL构建的逆胶束体系对纤维素酶的后萃效果较佳,且RL具有高生物降解性,低临界胶束浓度等优点,应用前景广阔.     

逆胶束体系中纤维素酶解特性研究

通过采用几种不同属性类型的表面活性剂构建逆胶束体系,以羧甲基纤维素为底物,研究了纤维素酶解的特性.通过电导率的测量,确定由CTAB、SDS、Tween-80和鼠李糖脂构造的逆胶束体系的最大增溶水量W0(W0=[H2O]/[SA])分别为15.2、20.1、2.3和40.3.在此条件下,考察了不同表面活性剂浓度和不同纤维素酶用量对逆胶束体系酶解行为的影响,并与水溶液体系的酶解反应进行对比.结果表明,单位底物条件下,纤维素酶用量为0.15 FPU/g,CTAB、SDS、Tween-80和鼠李糖脂浓度均为1 cmc时,逆胶束体系酶解产量最高,其中鼠李糖脂体系产量可达198.03 mg,分别比CTAB、SDS和Tween-80体系高了10.89%、31.09%和45.30%.CTAB、SDS、Tween-80和鼠李糖脂浓度为1 cmc时,其逆胶束体系酶解产量比水溶液体系分别高了34.36%、21.24%、11.44%和34.62%.在最佳表面活性剂浓度条件下单位底物酶用量为5 FPU时,逆胶束体系酶解反应从经济和糖产量方面考虑均为最适合.生物表面活性剂鼠李糖脂体系的产量高于3种化学表面活性剂体系,说明生物表面活性剂在构建逆胶束体系及增强逆胶束稳定性能上具有特殊的潜力.     

不同氧化剂辅助光催化反应对提高木质纤维素酶解效果的影响

木质纤维素以其可再生、丰富等优点成为可替代能源的理想选择,然而木质纤维素的致密结构使得后续的酶解过程极其困难,因此木质纤维素的预处理显得尤为重要.为了探讨氧化剂对光催化反应预处理木质纤维素的影响,在TiO₂/UV体系中添加不同种类的氧化剂对稻秆进行预处理,考察TiO₂/UV体系中影响光催化的因素〔ρ（TiO₂）、溶液pH及光催化时间〕,并进一步探讨在TiO₂/UV体系中添加O₃、SPC（过碳酸钠）、K₂S₂O₈及KIO₄等氧化剂对稻秆酶解效果的影响.结果表明:在TiO₂/UV体系中,当光催化时间为3 h、ρ（TiO₂）为10 g/L、pH为8时,稻秆的酶解效果最佳（310.17 mg/g）.TiO₂/UV/O₃光催化体系对稻秆的预处理效果强于TiO₂/UV/氧化剂体系,TiO₂/UV/O₃体系预处理稻秆酶解后产生的w（还原糖）最高,达到356.40 mg/g.TiO₂/UV/O₃体系预处理稻秆成分分析显示,木质素去除率为15.52%.FE-SEM（场发射扫描电镜）、FT-IR（红外光谱）及PXRD（X-射线粉末衍射）等表征分析结果表明,TiO₂/UV/O₃体系预处理能够对稻秆结构进行破坏.研究显示,TiO₂/UV/O₃光催化体系对稻秆进行预处理能够有效提高酶解效率.      

Tween 80和鼠李糖脂对稻草酶解的影响

采用纤维素酶促水解的方法,以稻草为底物,探讨了添加化学表面活性剂Tween 80和生物表面活性剂鼠李糖脂对酶解过程的糖产率、酶稳定性、纤维素转化率的作用以及对酶动力学特征和酶在纤维素上吸附的影响.结果表明,不同浓度的Tween 80和鼠李糖脂对稻草酶解有不同程度的促进,添加0.016%和0.048%Tween 80使糖产率分别提高18.07%和11.98%,而添加0.01%和0.03%鼠李糖脂使糖产率分别增加了23.01%和22.16%,相比较鼠李糖脂的效果更好.表面活性剂能有效增强酶的稳定性,添加高浓度表面活性剂的酶稳定性优于添加低浓度表面活性剂,添加浓度为0.048%的Tween 80得到最高相对CMCA(羧甲基纤维素酶活)108.06%和最高相对FPA(滤纸酶活)80.26%.表面活性剂能提高酶解反应的纤维素转化率,而且添加鼠李糖脂的转化率明显高于Tween 80.表面活性剂不仅能够提高最大反应速度并使米氏常数变大,而且显著地降低了纤维素酶在纤维素上的吸附.     

园林生物质中离子液体-复合菌剂共降解体系的筛选与构建

园林生物质的绿色高效降解是实现生态系统物质循环的重要环节,离子液体-生物酶作为环境友好型降解体系备受关注.通过合成1-丁基-3-甲基咪唑（[Bmim]）和1-乙基-3-甲基咪唑（[Emim]）型离子液体衍生物,比较了温和条件下各离子液体对园林生物质的溶解再生性.结合复合微生物菌剂开展酶解试验,通过考察酶解率、纤维素酶活力、降解失重率和木质素含量变化等,筛选并构建最优降解体系组合.结果表明,两种离子液体的盐取代物对园林生物质有着较好的溶解再生性,当质量分数为70%~80%时,[Emim]型离子液体-复合菌剂体系的酶解率和酶活力最高.在降解末期,[Emim]Ac_75%和[Emim]FeCl_4·75%体系的降解失重率分别为46.9%和52.6%,均为阳性对照组的1.6倍,同时木质素含量分别减少41.7%和47.2%.[Emim]FeCl_4·75%-复合菌剂体系对园林生物质有着更为显著的降解效应.     

反胶束体系中漆酶催化愈创木酚的研究

采用4种不同属性类型的表面活性剂(CTAB,Tween-80, AOT以及鼠李糖脂)构建反胶束体系,以木质素模式物愈创木酚为底物,研究了漆酶在反胶束环境中催化愈创木酚的特性,通过对不同反胶束环境中漆酶酶活的对比,确定在4种反胶束体系中,适合酶解反应的最佳表面活性剂浓度和对应的最佳含水率w0.分别为:CTAB浓度20mmol/L,w0=20;Tween 80浓度50mmol/L,w0=25;AOT浓度30mmol/L,w0=10;鼠李糖脂浓度10mmol/L,w0=30.并考察了表面活性剂类型属性对愈创木酚在反胶束体系中酶解行为的影响和底物动力学.结果表明,最佳表面活性剂浓度以及对应的最适含水率条件下,阴离子表面活性剂AOT和鼠李糖脂的反胶束体系中愈创木酚底物的催化效果较好,鼠李糖脂反胶束体系中底物的催化率最高,反应6h后分别比 CTAB、Tween-80以及AOT反胶束体系中的转化率高44.12%、34.6%、29.43%.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Chlorobenzenes in waterweeds from the Xijiang River （Guangdong section） of the Pearl River

The Xijiang River is the major source of water for about 4.5 millions of urban population and 28.7 millions of rural population. The water quality is very important for the health of the rural population. The concentration and distribution of chlorobenzenes (CBs) in both water and waterweeds collected from 4 stations in the Xijiang River (Gangdong section) of the Pearl River in April and November were determined. The result showed that nearly every congener of CBs was detected. The total contents of CBs (∑CBs) in the river water ranged from 111.1 to 360.0 ng/L in April and from 151.9 to 481.7 ng/L in November, respectively. The pollution level of CBs in the water in April was higher than that in November. The contents of ∑ CBs in waterweeds ranged from 13.53×102 μg/g to 38.27×102μg/g dry weight (dw). There was no significant difference between April and November in waterweeds. The distribution of CBs in roots, caulis, and leaves of Vallisneria spiralis L. showed different patterns. The leaves mainly contained low-molecular-weight CBs(DCBs), whereas the roots accumulated more PCBs and HCBs. The average lgBCFlip (bioconcentration factor) of CBs ranged from 0.64 to 3.57 in the waterweeds. The spatial distribution character of CBs in the Xijiang River was: Fengkai County ＜ Yunan County ＜Yun'an County ＜ Gaoyao County according to the ∑CBs, and the pollution deteriorated from the upstream to the downstream of the Xijiang River. Further analysis demonstrated that the discharge of waste containing CBs may be the main source of CBs pollution in the Xijiang River.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

Effects of arsenic on seed germination and physiological activities in wheat seedlings

The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Sustainability： A view from the wind-eroded field

This article explores the assessment of sustainability in fields subject to wind erosion. In the first part, simple sustainability audits are examined, as of soil depth and nutrients. Direct measurement of these characteristics has many problems, largely because of huge variability in space and time at all scales. Modelling still has its problems, but it may be possible to overcome many of them soon. It is true that wind erosion preferentially removes soil nutrients, but there are imponderables even here. The nutrient balance in many of these soils includes considerable input from dust. In West Africa, it has been shown that the amounts of calcium and potassium that are added in dust are sufficient to fertilize dispersed crops. In mildly acidic sandy soils, such as those found on the widespread palaeo- aeolian deposits, much of the phosphorus is fixed and unavailable to plants by the time it is removed by wind erosion, so that erosion has no added downside. Most of the nutrients carried by dust have been shown to travel close to the ground （even when they are attached to dust-sized particles）, and so are trapped in nearby fallow strips, and are thus not lost to the farming system. Second, the sustalnabillty of a whole semi-arid farming system is explored. Wind erosion in semi-arid areas （like China, the Sahel and Norflawestern Europe） generally takes place on aeolian deposits of the recent geological past. Most of these soils are deep enough to withstand centuries of wind erosion before they are totally lost to production, and some of these soils have greater fertility at greater depth （so that wind erosion may even improve the soil）. Finally some remarks are made about environmental change in relation to sustainability.     

Amplification of plasmid DNA bound on soil colloidal particles and clay minerals by the polymerase chain reaction

Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.