固定化纤维素酶催化反应动力学模型研究

建立固定化纤维素酶反应动力学模型，在此基础上系统研究了席勒模数、产物竞争性抑制、体系宏观底物浓度等因素对球形载体内部底物分布的影响，并讨论了各因素对固定化纤维素酶效率因子的影响。结果表明席勒模数增大使载体内底物浓度降低，效率因子减小；产物竞争性抑制增大使载体内底物浓度升高，对效率因子的影响与席勒模数和体系宏观底物浓度有关，共存的产物竞争性抑制和内扩散限制之间存在相互减弱对方影响的效应；体系宏观底物浓度增大使载体内底物浓度升高，效率因子增大，可以减弱席勒模数与产物竞争性抑制的影响。     

南瓜籽粕酶法制备血管紧张素转化酶抑制肽工艺优化

用中性蛋白酶水解南瓜籽粕,制备血管紧张素转换酶（angiotensin-converting enzyme,ACE）抑制肽,是南瓜籽粕蛋白深度开发的途径之一。为了探寻南瓜籽粕酶法制备ACE抑制肽的最佳工艺,该文以ACE抑制率为响应值,用响应面分析法研究酶浓度、底物质量浓度和水解时间等因素对酶解产物的ACE抑制活性的影响,优化制备工艺。结果表明,各因素对制备ACE抑制肽的活性具有极显著影响（P<0.001）。获得中性蛋白酶水解南瓜籽粕制备ACE抑制肽的最佳工艺条件为：酶体积分数为4.8%、底物质量浓度为4.0g/100 mL、水解时间为320 min。在此条件下,南瓜籽粕蛋白酶解产物对ACE的理论抑制率最高可达80.0％,验证值为80.56％±0.23%,预测模型可靠性高,可应用于南瓜籽粕ACE抑制肽的酶法制备。通过优化,提高了南瓜籽粕ACE抑制肽的活性。     

低温辐射聚合法固定糖化酶

本文应用低温辐射技术诱导不同亲、疏水性高分子玻璃态单体聚合固定黑曲糖化酶,研究了不同实验条件对辐射聚合固定化黑曲糖化酶相对活性的影响。结果表明,在4种亲疏水性程度不同的破璃态高分子单体(2-hydroxyethyl methylacrylate和Polyethylene glucol dimethacrylate 9G,4G,2G)中,亲水性的9G、HEMA的固定化效果较好;在高分子单体浓度为50％,相应聚合物载体空孔率为32％时,固定化糖化酶与底物10次反应的平均活性产率最高,达70％左右;当辐照温度为-78℃。辐照剂量为3×10~4Gy,pH为4.5时,可以得到相对活性较高的固定化黑曲糖化酶。文中还对影响固定化糖化酶相对活性的原因进行了探讨。     

碱性脂肪酶固定化条件及其催化生物柴油的研究

该文以改性的硅胶为载体,通过戊二醛交联固定化碱性脂肪酶,得到较佳固定化条件：当戊二醛浓度为0.8 g/L,给酶量为30 U/g时,酶活回收率效率达到90%以上。通过改变溶剂的种类、给酶量、含水率、底物摩尔比、甲醇的流加方式等参数,考察了脂肪酸和甲醇在固定化碱性脂肪酶催化下合成生物柴油的工艺条件,试验结果表明在20 mL正己烷,给酶量7.5 g（12 U/g）,脂肪酸10 g,酸醇摩尔比为1︰1.2,含水率4%条件下,分3次加入甲醇,40℃反应8 h,反应体系酯化率达到了82%。     

挥发性有机酸对产沼气效果的模拟试验

两相厌氧生物处理工艺在废弃物资源化利用中得到广泛应用。为了摸清产酸相的主要产物在产气过程中的效应,该文利用甲酸、乙酸、丙酸和丁酸等4种有机酸模拟产酸过程中的主要酸化产物,以活性污泥为接种物,设计单因素试验和正交试验,研究了在中温条件下,4种有机酸单一作用条件下和混合作用条件下,甲烷日产气量和累积产气量的变化。结果表明：单一有机酸作底物时,存在一个浓度阈值,高于此值会抑制甲烷产生,低于此值,产气效果随着酸浓度增大而提高;有机酸共同存在时,可以产生协同优势,其中乙酸的产气优势高于丁酸,丙酸具有抑制作用;4种单一酸中,单位浓度下乙酸产气效果最好,甲酸产气量最大,甲酸积累不易对发酵过程产生抑制作用,而丙酸累积最易造成抑制。因此,建议在沼气工程中适当调整产甲酸、乙酸和丁酸较多的发酵物料浓度,从而提高产气效率。     

高CO2浓度和遮荫对小麦叶片光能利用特性及产量构成因子的影响

CO2和光能是植物光合作用的动力和底物,它们的变化必然引起植物光合特性和生长的变化。研究大气CO2浓度和光强变化对植物光合生理的影响,有利于认识作物对全球生态变化的生理响应机制。试验以高大气CO2浓度和遮荫为处理手段,通过测定小麦(Triticum aestivum)旗叶的光合气体交换参数、光强光合速率响应曲线和产量构成因子,分析光强光能利用效率之间的关系,研究高大气CO2浓度(760μmol.mol 1)和遮荫对小麦叶片光合特性及产量构成因子的影响。结果表明,高大气CO2浓度下,小麦叶片的净光合速率(Pn)增加;同时最大净光合速率(Pnmax)、光饱和点(LSP)、光补偿点(LCP)显著升高;遮荫处理使小麦叶片的Pnmax、LSP、LCP降低。正常光照下大气CO2浓度升高使小麦叶片呼吸速率(Rd)显著下降,遮荫后大气CO2浓度升高对Rd无显著影响。大气CO2浓度升高能显著提高小麦叶片表观量子效率(AQY),而遮荫对AQY的影响因大气CO2浓度而异,高大气CO2浓度下遮荫使AQY显著提高,正常大气CO2浓度下遮荫则使AQY明显下降。高大气CO2浓度下遮荫使小麦株高、穗长增加,而穗粒数、单株穗粒重、千粒重减小。受光合特性的变化和光强限制,高大气CO2浓度下遮荫使小麦叶片呼吸增强,导致Pn下降,不利于干物质积累和籽粒产量的形成。     

塔里木河上游连作棉田土壤脲酶动力学特征与环境因子的相关分析

研究土壤酶学特征的变化对于探讨人类活动对土壤生态系统的影响具有重要的意义。以阿拉尔垦区4个不同连作年限棉田为研究对象,分析了各连作年限棉田不同土层深度土壤脲酶活性、动力学以及土壤理化因子特征,研究了土壤酶动力学特征及其与理化因子的对应关系。结果表明:阿拉尔垦区不同连作年限棉田脲酶活性随土层深度逐渐减弱,随着连作年限增加,0—20cm土层土壤脲酶活性呈先降低后升高趋势,20—50cm和50—80cm为先升高后降低再升高的变化规律;4个不同年限棉田土壤脲酶活性依次为:20a棉田15a棉田10a棉田5a棉田;各连作年限棉田脲酶酶促反应总趋势为随底物浓度增高反应初速度逐渐增大。5a,10a,15a,20a棉田V_9_(_(max)),V_(max)/Km值表现出明显的随年限增加而呈先升高后降低的变化趋势,而K_m值则显现出随连作年限增大脲酶与底物结合度越低的规律;相关性分析结果表明,V_(max)与速效磷、土壤含水量正相关,与电导率负相关,K_m与各土壤理化因子相关性不大,V_(max)/Km与速效磷、土壤含水量、pH值均呈正相关关系。总之,土壤酶动力学特征受速效磷、土壤含水量、pH值和电导率的影响较大。     

锌对汞毒害小麦幼苗生长及生理活性的影响

采用学人培养法研究了汞对小麦幼苗的影响以及锌对汞毒害的缓解效应。结果表明,随着汞浓度的增加,细胞膜透性增大,MDA积累增加,SOD和POD活性上升,幼苗生长受到抑制,且与汞毒害呈正相关。当在汞胁迫溶液中加入10^-3mol/L的Zn^2 ,能使汞毒害引起的生理生化变化得以没程度的恢复,但随汞浓度的升高,锌的这种缓解效应逐渐减弱。     

复合材料对砷污染土壤稳定效果及其影响因素的研究

添加Fe S、电石渣、菌渣复配材料稳定处理砷污染土壤,采用国标硫酸-硝酸法(SNP)和美国毒性浸出程序(TCLP)检测处理前后污染土壤砷的浸出浓度,依据浸出浓度评价稳定效果,并探讨土壤含水量、土壤pH、竞争性离子、反应时间、污染初始浓度对砷稳定效果的影响。结果表明:(1)SNP法和TCLP法浸提土壤,砷的浸出浓度为污染原土>对照处理>>稳定处理,稳定处理有效降低砷的浸出毒性。(2)砷的稳定效果影响因素研究表明,土壤含水率以30%为宜;土壤pH于2.20~9.85时砷的稳定效果良好,且pH=6.05时最佳,pH高于9.85至12.01时稳定效果减弱;竞争性离子对土壤砷稳定效果的抑制作用表现为PO_4~(3-)垌SO_4~(2-)≈NO_3~->Cl~-;土壤砷的稳定效率随反应时间先上升后平缓,于15 d后趋于稳定并持续至120 d;土壤中砷的污染初始浓度为506 mg kg~(-1)、833 mg kg~(-1)、2951 mg kg~(-1)和5290 mg kg~(-1),砷的稳定效率分别为92.36%、90.53%、55.57%和47.54%,稳定效率随着污染初始浓度升高而降低,稳定药剂适用于一定污染浓度范围。     

秸秆固态发酵酒精过程中湿度变化的研究

研究了在转轴式反应器中以秸秆为原料,接种康氏木霉TR6(Trichoderma koningii)和耐高温酵母CB2(saccharomyces cerevisiae)同步固态发酵酒精的过程中,底物湿度对生物量、纤维素酶活和酒精产量的影响。结果显示：产纤维素酶的最适底物湿度和产酒精的最适底物湿度并不一致;试验研究得到了发酵温度对底物湿度变化的影响最大,通气速率影响次之,菌体呼吸强度的影响最小。     

In-Vehicle Measurement of Particle Number Concentrations on School Buses Equipped with Diesel Retrofits

Many metropolitan school districts worldwide operate bus fleets with older diesel school buses. Emission reduction strategies such as the diesel retrofits promise substantial reductions in particulate mass emissions for older diesel engines. Recent studies suggest, however, that particle number concentration is a more important factor than particle mass in developing emissions standards and predicting adverse health effects. In-vehicle particle number concentration measurements on clean diesel, retrofitted diesel, and non-retrofitted diesel school buses were compared to estimate retrofit effectiveness in reducing in-vehicle passenger particle exposures. The retrofits were shown to provide a 15% to 26% decrease in in-vehicle particle number concentration levels between the retrofitted and non-retrofitted buses. Furthermore, the retrofitted diesel buses had average in-vehicle particle number concentrations near the average concentrations for the newer model, clean diesel buses. The average particle number concentrations for the non-retrofitted diesel buses were 1.5 to 2 times higher than the concentration measured from the retrofitted diesel buses. Moreover, a two-fold increase was observed for the morning commute samples over the afternoon commuter samples. Particle number concentrations were also significantly affected by engine age, bus idling behavior, and ambient particle concentrations along bus routes.     

超声波对固体废弃物酸化过程的调节作用

为缓解固体有机物酸化过程中产生的酸抑制,该文基于有机酸的产生和扩散方式,提出有机酸产物薄膜的假设,并利用超声波直接辐射和改进处理的方法处理酸化基质,比较处理前后酸化基质的物性变化及进一步的发酵性能。试验结果表明,超声波直接辐射可脱附积累在基质颗粒表面的有机酸,使基质发酵10 d的挥发性固体日降解速率从未处理的0.8%提高到1.3%。为强化超声波空化效应和去除有机酸,将基质稀释后超声辐射20 min并增加过滤的改进超声波处理过程可使基质发酵10 d的有机酸增长率、挥发性固体降解率分别从未经超声波处理的166.7%、17.0%提高到732.0%、26.7%。改进超声波处理过程可有效缓解产物抑制,促进固体有机物的厌氧酸化性能,提高酸化速率。     

Growth of Impatiens ‘Accent Orange’ In Two Compost Products

Growth of Impatiens wallerana Hook. ‘Accent Orange’ was compared in two compost products made of biosolids and yard trimmings but differing in final particle size. The first product was screened to pass a 19 mm screen while the second product was screened to pass a 13 mm screen. Treatments consisted of 100 percent compost or substrates in which compost was combined with control substrate components at 60 percent, 30 percent, or zero percent compost. Shoot dry mass and size increased linearly as the percentage of each compost product in the growing substrate increased from zero to 100 percent. Final substrate electrical conductivity (EC), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations also linearly increased as the percentage of each compost product increased in the substrate. Final plant size and shoot dry mass were significantly greater in the 13-mm product than in the 19-mm product. However, both the 13-mm and 19-mm products at 100 percent produced larger impatiens ‘Accent Orange’ plants compared with plants grown in zero percent compost.     

复垦基质重金属污染的植物修复试验研究

该文研究了粉煤灰加酒糟和粉煤灰加污泥两种基质对甘蓝、小白菜和油菜生长的影响,并通过计算吸收系数、转运系数和吸收模量讨论了甘蓝、小白菜和油菜对基质中重金属Cd、Cu、Zn的修复情况.结果表明:甘蓝、小白菜和油菜3种作物的吸收系数、转运系数和吸收量系数均随着时间的延长而增大,说明作物生长后期对重金属Cd、Cu、Zn的修复要好于前期;从不同作物对重金属Cd、Cu、Zn的修复情况看,甘蓝、小白菜和油菜对Cd具有良好的修复效果,其中小白菜对Cd的修复能力强于甘蓝和油菜,油菜对基质中重金属Cu具有一定的修复潜力,而甘蓝对Zn的吸收要好于小白菜和油菜;由于吸收模量考虑了作物地上部的生物积累量,也考虑了根层中重金属的总量,从而能从对重金属的实际修复效果方面更好地评价植株的吸收能力,是衡量植物修复重金属能力的一个理想指标.     

中性蛋白酶水解鸡骨泥制备短肽工艺优化

为了探究酶法制备鸡骨泥短肽的最佳工艺,该文研究了以中性蛋白酶酶解鸡骨泥时各因素对短肽得率和羟自由基清除率的影响,以及鸡骨泥肽清除超氧阴离子自由基和1,1-二苯基-2-三硝基苯肼自由基(2,2-diphenyl-1-picrylhydrazyl)的能力。试验探究了酶解过程中不同底物浓度、酶浓度、反应温度和反应时间对短肽得率和羟自由基清除率的影响,采用响应曲面优化得到了以短肽得率为目标的中性蛋白酶酶解鸡骨泥的最优工艺,当反应液p H值为7.2,反应温度42℃,反应时间2 h,底物质量分数5%,酶添加量200 mg/g,该条件下制备鸡骨泥肽,测得其短肽得率为56.16%,羟自由基清除率为54.12%。采用该酶解工艺制备鸡骨泥肽,测得其对超氧阴离子自由基最高清除率为56.01%,对DPPH自由基最高清除率为81.57%,说明鸡骨泥肽具有一定的抗氧化活性,研究结果为酶法制备鸡骨泥肽提供参考。     

Effects of plants on net mineralization of nitrogen in forest soil microcosms

Summary The effects of plant roots on net N mineralization were examined by comparing soil microcosms with and without plants. Additionally, inorganic N amendments were used to test for competition for N between plants and microorganisms. Daily watering and the application of suction to microcosms eliminated the effects of transpiration on soil moisture content. Monthly litter collections reduced the influence of the aboveground portions of plants. Plants decreased net N mineralization by 23% during days 0–114 and then increased net mineralization by the same amount during days 144–124. Root-free soil collected from with-plant microcosms on day 244 evolved 24% more CO₂ in laboratory incubations than soil from without-plant microcosms. This indicates that plants had increased substrate availability to soil microorganisms. Inorganic N amendments had no significant effects on the microcosms or on laboratory soil incubations. Evidence is most consistent with the hypothesis that plant roots increased microbial activity due to the increased substrate availability. Different net N mineralization rates probably resulted from changes in the substrate C : N ratio.     

低氮胁迫下小麦抑草作用的化感效应与资源竞争分析

化感效应和资源竞争在作物抑草中起重要作用。为区分低氮胁迫下小麦抑草作用的化感效应与资源竞争,以强化感小麦品种‘115/青海麦’、‘92L89’和弱化感小麦‘抗10103’为材料,设置氮水平为25 mg·L-1、50mg·L-1、100 mg·L-1和200 mg·L-1的水培试验,通过小麦与看麦娘共培、应用含小麦根系分泌物的小麦-看麦娘共培液处理看麦娘,分别测定了小麦对看麦娘的生物干扰作用、化感效应及资源竞争效应。结果表明,不同化感潜力的小麦对看麦娘的抑制能力存在显著差异,抑制率大小为‘115/青海麦’(55.1%~73.9%)‘92L89’(48.9%~65.9%)‘抗10103’(15.4%~45.5%),且抑制率随氮水平的降低而增大。在小麦的抑草作用中,化感效应与资源竞争并存。低氮胁迫条件下,强化感小麦抑草能力增强主要通过提高化感效应实现;弱化感小麦抑草能力增强主要通过提高资源竞争实现。不同化感潜力小麦的抑草作用在低氮胁迫下表现出不同的生态策略。小麦抑草作用的化感效应均随氮水平降低而增大,其抑制率随氮水平的变化可用一元二次方程加以拟合。     

Multiple-substrate enzyme assays: a useful approach for profiling enzyme activity in soils?

This study focuses on the applicability of multiple-substrate enzyme assays to simultaneously determine various soil enzyme activities within one assay. Mineral soils from agricultural field sites differing in soil properties and management were used to optimise substrate composition and concentration of 4-methylumbelliferone and 7-amino-4-methylcoumarin derivatives as model substrates. In contrast to conventional assays, enzyme activity was measured at soil pH since optimum pH is not more applicable using a multiple-substrate approach. Furthermore, enzyme activity was not calculated from the product formed but from substrate decrease. After incubation the added substrates were re-extracted, separated by high-performance liquid chromatography and quantified by UV-absorption at 320 nm. This approach allows simultaneous measurement of the activity of β-d-glucosidase, N-acetyl-β-d-glucosaminidase, β-d-glucuronidase, β-d-xylosidase, phosphomonoesterase, sulfoesterase and leucine-aminopeptidase within one assay and with sufficient accuracy. However, incomplete re-extraction due to adsorption of substrates to the soil matrix was observed. In addition, certain competitive inhibition effects due to chemically similar substrates were found. Compared to conventional methods, no distinct differences in enzyme activity profile were detected, with both assays—conventional and multiple-substrate approach—leading to similar differentiation among the investigated soils. In conclusion, the multiple-substrate approach may serve as time-saving alternative to standard enzyme assays in mineral soils. Certainly, since the multiple-enzyme assay is conducted at soil pH, the procedure leads to reduced comparability of soils with contrasting pH values.     

固体稀释倍数和超声波对豆渣厌氧发酵酸化过程的影响

为了优化超声波对固体废弃物酸化过程的调节作用,缓解酸化产物抑制,该文研究超声波处理时不同稀释倍数对基质性质的影响及对处理后基质发酵性能的影响,根据基质的挥发性有机酸去除率和发酵性能选取较佳的超声波处理参数。试验结果表明,超声波对不同浓度酸化基质的处理可去除有机酸中80%以上的非电离有机酸,减小对微生物的毒害,同时可减小基质的颗粒尺寸。处理后的基质经10 d发酵以评价不同浓度条件下的酸化性能,当基质挥发性有机酸质量浓度在18.8 g/L左右时,将基质稀释至固体质量浓度为46 g/L后再进行超声波处理,基质的挥发性有机酸增长率和挥发性固体降解率可分别从仅经过超声波辐射处理的51.8%、14.7%提高到197.4%、26.8%,表现出较佳的处理性能。可为超声波调节固体废弃物酸化过程提供参考。