共价氢化物在光度分析中的应用

本论文由两部分工作组成。第一部分（铋化氢-二乙氨基二硫化甲酸银分光光度法测定铋）提出一个测定铋的新的分光光度方法，对影响方法准确度和精密度的各种因素进行实验，确定了适宜分析条件。用硼氢化钾-氯化钠-铝粉（重量比2:1:5）还原片，0.5N盐酸介质、15-25 ℃时，将铋离子转化为铋化氢，用5.0毫升0.2%的二乙氨基二硫化甲酸银氯彷溶液吸收显色。有色溶液最大吸收波长为425毫微米，摩尔吸光系数为4.6 * 10~4升。厘米~(-1)·摩尔~(-1)。铋量0-20微克符合比尔定律。经过对发光材料、铝合金和矿石中铋的测定，证明此方法有较好的实用价值。第二部分（砷、锑、铋的氢化物与二乙氨基二硫代甲酸银形成的有色物质性质的探讨）针对文献中砷化氢与AgDDC形成有色物质性质的两种不同看法，结合我们在AgDDC分光光度法测定砷、锑、铋中观察到的现象，用分光光度法对三种有色溶液的吸收光谱进行分析和讨论。实验证明，砷、锑、铋的氢化物与AgDDC形成的有色物质不可能是下列络合物：1、砷、锑、铋与二乙氨基二硫代甲酸（简称HDDC）或其它配位体形成的络合物；2、砷、锑、铋或银与HDDC形成的同核或异核的多核络合物；3、砷、锑、铋与HDCC及有机碱形成的三元络合物。同时指出，砷、锑、铋的氢化物与AgDDC之间可能发生的氧化还原反应，反应形成的有色物质属於银溶胶。由於上述三种氢化物还原AgDDC的能力不同，故所产生的银溶胶分散程度不同，而具有各自特征的颜色及吸收光谱。我们结合实验现象对砷的吸收曲线有两个吸收峰的问题进行了讨论，指出410毫微米波长处的吸收峰是砷的有色物质本身固有的，是由另一种分散程度的银溶胶产生的。

硒及其形态分析方法的研究

本论文由四部分组成。第一部分是天然水中痕量硒的分析方法研究。针对目前天然水样中硒含量低，难于测出的问题，本文提出了将水样用氨水调制弱碱性后，减压滤过以纸粉的载体的氢氧化镧吸附层，然后将沉淀用稀盐酸洗下，调至0.2N硫酸－2%酒石酸的酸度，使用电剂硼氢化钾进行氢化物发生，将生成的硒化氢导入邻菲罗啉－联(III)吸收液显色，在波长510nm处比色测定的方法。此方法富集及分析速度快，富集倍数大，灵敏度高、重现性好。每次最多可富集1,001ml水样，滤速可达40ml/min，工作曲线相关系数达0.999，检出限可达0.1ppb。方法 作简单，易于掌握，不需特殊试剂，适应性强。第二部分是关于几种含硒样品消解方法的讨论。当前有大量文献报道在测定样品中的硒的过程中，消解方法难掌握，硒易损失影响测定的准确性等问题，但尚未有关于含硒样品消解条件的详细而系统的报道。本文通过对常压下各种混酸法、钼酸钠混酸法的消鲜温度、浓度、时间等影响因素的讨论，找出了各种消解体系中的最佳消解条件，初步探讨了硒的测定过程中回收率低的原因及防止硒损失的方法。同时，本文还比较了混酸法、钼酸钠混酸法及高压法的优缺点及应用范围，为硒的测定的样品消解前处理中所存在的问题做出了系统的答案。第三部分是硒酵母中硒的形态分析。针对进一步研究硒的生物无机及医学等方面作用的需要，我们对药用硒酵母中硒的形态分析方法进行了研究。根据制备方法，可认为硒酵母中存在硒的形态是硒(N)及硒的有机化合物如硒代氨如硒代氨基酸等。实验结果表明，常压下各种溶液浸取硒(IV)的回收率均较低，且证明是酵母对硒(IV)的吸附所至。用0.5N氨水加热加压浸取硒酵母中硒(IV)的效果显著，可达定量浸出。通过氨水加压浸取后，氢化物发生-分光光度法测定硒(IV)，然后用5:1的硝酸－高氯酸混酸消解样品后测定总硒，差减可得有机硒含量，从而完成硒酵母中硒的形态分析。硒的形态分析方法的建立有利于研究不同形态硒对人体的作用，促进医学界对硒的作用研究的深入。第四部分是几种氢氧化物对硒(IV)的吸附机理的探讨。目前有委多文献介绍或使用了用铁(III)、镧(III)等氢氧化物分离富集硒的方法，关于其吸附机理尚未见报道。本文在使用氢氧化镧做富集剂吸附富集水中硒的基础之上，对硒在几种氢氧化物上的吸附情况进行了研究。认为其吸附机理主要是在大表面积的絮状沉淀存在条件下，通过静电吸引从而达到对硒(IV)的定量化学吸附。选用较有代表性的氢氧化铁沉淀所做的吸附曲线及吸附速率实验也证明了这种吸附反应有高吸附速率，大吸附量的特点，有助于进一步认识氢氢化物用为痕量元素富集剂时的作用。

重金属污染土壤毒性的发光菌与斜生栅藻诊断

重金属作为土壤污染的重要污染物，给环境和人类的健康带来严重危害，目前传统的研究方法已不适于土壤污染的快速诊断，如何建立一个新的诊断方法是人们面临的艰巨任务。水生生态毒理学在其长期的发展过程中已形成一系列标准的实验方法,而且具有快速、敏感等优点,但这些方法主要用于水体中污染物的毒性诊断,本研究的主要目的就是应用水生生态毒理学方法对重金属污染土壤的毒性进行诊断,并且确定土壤污染的警戒值,为土壤清洁标准的建立提供依据。实验选取Cd、Cu、Zn、Pb作为土壤污染的污染物,采用清洁土壤人工投加污染物的方法,对4种重金污染的3种土壤采用两种毒性诊断方法进行毒性诊断。首先探讨了应用发光菌法和斜生栅藻增长抑制实验对重金属污染土壤进行毒性诊断的可行性,结果表明2种方法是可行的,并且确定了最佳平衡时间为24小时,最佳浸提时间为2小时。变换不同的浸提方法表明0.1N HCL为最佳的浸提剂,剂量效应曲线表明土壤的重金属投加量与效应间存在明显的相关性。相同重金属条件下不同土壤的EC_(50)依次为粟钙土>暗棕壤>草甸棕壤;同一土壤条件下不同金属的EC_(50)依次为Pb>Cu>Zn>Cd。同一种金属不同诊断方法、不同诊断参数的敏感性依次为斜生栅藻细胞数增长率>斜生栅藻光密度增长率>发光菌相对发光度。对复合污染的研究表明,复合污染条件下,金属间存在明显的协同作用,使土壤的毒性明显增加。本研究首次将水生生态毒理学方法用于土壤污染毒性诊断,并提出了不同土壤、不同诊断方法的土壤污染的警戒值,为土壤的优先修复提供奠定了基础。

黑土中铜的环境容量

本文以土壤一植物系统为中心，通过铜在三个类型区黑土中的作物效应，作物残毒，环境效应，封对铜的自净能力，综合确定了黑土中铜的临界含量，根据野外调查和室内模拟的各项物质平衡参数，代入数学模型，计算出不同年限黑土中铜的环境容量。作物盆栽（春小麦、大豆）试验表明，作物受铜害的起始浓度在200-400ppm以上。以作物减产10%为依据，经相关方程计算，黑土中铜作物效应的临界值为348.46ppm（全铜），和217.93ppm（有效铜，0.1N Hcl）。在本实验土壤铜浓度范围内（0-1000ppm），作物籽实，茎（叶、荚）中铜含量很少超过20ug/g毒性标准。土壤对铜的吸附一解吸试验表明，代表土壤对铜自净能力的指标一固态吸附量在本实验条件下为806.77-1456.16ug/g土。铜对环境影响试验表明，土壤投加铜1204.09ppm和土壤投加铜200ppm不导致地下水和地表水超标。综合以上各个单一体系的临界指标，选择限制性因子，确定黑土中铜的临界值为348.46ppm（全铜）。根据野外调查和模拟的各项物质平衡参数，经数学模型计算出了黑土中不同年限的变动容量（Q）和总容量（Q总）。如，t = 50年，Q = 1700.58g/亩·年，Q总 = 85029 g/亩。

Distribution of organic and reduced sulfur forms in marsh soils of coastal Louisiana

Soil samples from a Louisiana Barataria Basin brackish marshes were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester-sulfate sulfur, and carbon-bonded sulfur. Inorganic sulfur composed 13% of total sulfur in brackish marsh soil with HCl-soluble sulfur representing 63–92% of the inorganic sulfur fraction. AVS represented less than 1% of the total sulfur pool. Pyrite sulfur and elemental sulfur together accounted for 8–33% of the inorganic sulfur pool. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, was the most dominant pool representing the majority of total sulfur in brackish marsh. Results were compared to values reported for fresh and salt marshes. Reported inorganic sulfur fractions were greater in adjacent marshes, constituting 24% of total sulfur in salt marsh, and 22% in freshwater marshes. Along a salinity gradient, HCl-soluble sulfur represented 78–86% of the inorganic sulfur fraction in fresh, brackish, and salt marsh. Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was the major constituent (76–87%) of total sulfur in all marshes. Reduced sulfur species, except elemental sulfur, increased seaward along the salinity gradient. Accumulation of reduced sulfur forms through sedimentation processes was significant in marsh energy flow in fresh, brackish and salt marshes.

南果梨红果皮中花青素提取工艺研究

本实验研究了南果梨红果皮中花青素提取条件对其提取量的影响。以南果梨红果皮中花青素提取量为技术指标,采用正交试验法,考察各工艺条件对提取效果的影响,确定了南果梨红果皮中花青素提取的优选条件。结论表明,0.1%HCl-甲醇溶液(pH4.0)以1:4的料液比混合后,在50℃下浸提两次,共计240min,提取量可达40mg/g,其检测数据可靠,提取方法简单合理。

Real-time immunoassay of ferritin using surface plasmon resonance biosensor

A surface plasmon resonance (SPR) biosensor was used for the first time to determine the concentration of ferritin in both HBS-EP buffer and serum. The monoclonal antibody was immobilized on the carboxymethyl dextran-modified gold surface by an amine coupling method. The interaction of antibody with antigen was monitored in real-time. The signal was enhanced by sandwich amplification strategy to improve the sensitivity and specificity of the immunoassay, especially in serum. The linear range of the assay in serum is over 30-200 ng ml with the detection limit of 28 ng ml(-1). The sensitivity, specificity, and reproducibility of the assay are satisfactory. The analyte and enhancement antibody-binding surface could be regenerated by pH 2.0 glycine-HCl buffer and the same antibody-immobilized surface could be used for more than 50 cycles of ferritin binding and regeneration.

Recovery of silver (I) using a thiourea-modified chitosan resin

This work describes the preparation of a chelating resin from chemically modified chitosan. The resin was synthesized by using O-carboxymethylated chitosan to cross-link a polymeric Schiffs base of thiourea/glutaraldehyde and characterized by IR. Batch method was applied for testing the resin's adsorption behavior. Adsorption experiments showed the resin had good adsorption capacity and high selectivity for Ag(I) in aqueous solution. The maximum uptake of Ag(I) exhibited was 3.77 mmol/g, at pH 4.0. The results also indicated that the adsorption process was exothermic and fit well with the pseudosecond-order kinetic model. Ag(I) desorption could reach 99.23% using 0.5 M thiourea-2.0 M HCl solution. (C) 2010 Elsevier B.V. All rights reserved.

运用MC-ICP-MS测定天然样品的锂同位素组成

自然界锂同位素分馏强烈，这使得它在很多方面都得到了应用，如地球化学、天体化学和核工业等。所有这些领域都要求精确的测定6Li/7Li的比值。但由于锂是微量元素，而且在测试过程中还存在明显的干扰，因此在进行锂同位素比值测定之前必须对样品进行分离和富集。本文以锂元素标准样品和钾、钠、钙、镁元素标准样品的混合溶液为主要研究对象，采用阳离子交换树脂AG-50W-X8来分离富集锂，探索在不同淋洗介质条件下锂分离纯化的最佳介质条件。初步得出以下结论： 1、本次研究建立了相对简单、高效的锂同位素分离方法。用单一的柱子分离、提纯样品锂；用低浓度的盐酸（0.15M HCl）直接作为淋洗介质，操作过程简单。 2、对锂同位素比值测定产生潜在影响因素，如基体效应、回收率、流程空白等进行了实验研究，证实这些影响因素对于本次研究所建立的方法来说都是可以忽略不计的。 3、用MC-ICP-MS测定样品的锂同位素组成，分析结果的准确度和精度与现阶段所报道数据相同。测定海水的锂同位素组成（+31.6±1.0‰，2σ）与Tomoscak 等（+31.8±1.9‰，2σ）的分析值相近。 4、该方法也适用于低含量的样品。我们分离并测定了不同类型样品的锂同位素组成，样品锂含量在0.064µg/g和132µg/g之间，说明该方法也同样适用于低含量地质样品的分析测定。

锡在流体和花岗质熔体间分配行为的实验研究

锡矿床是与花岗岩在时间、空间、成因上有着密切联系的典型矿种之一。与锡矿有关的花岗岩多具有过铝、富钾、硅含量高的特征。传统观点认为与锡矿有关的花岗岩主要是S型花岗岩，可是近年在国内外相继发现了许多具有重要经济价值的锡矿床与富碱侵入岩有着密切成因联系。与富碱侵入岩有关的锡成矿作用日益受到地质学家的重视，锡矿床与富碱侵入岩的关系已成为研究热点之一，相关的研究工作虽然取得了很大的进展，但是富碱侵入岩体能否分异出富锡成矿流体还存在争议。研究表明，与岩浆岩有关的成矿与岩浆演化过程中成矿元素在流体-熔体相间的分配行为有着密切的关系。成矿元素在流体-熔体相间的分配行为除受到温度、压力及氧逸度等物理化学条件的制约外，还受到岩浆熔体成份及岩浆分异出来的流体化学组成的影响。以往有关锡在流体-熔体相间分配行为的实验研究主要侧重于改变流体相来观测锡的分配系数，且多为单一的含氯或含氟岩浆体系，这制约了对岩浆演化过程中元素在流体-熔体相间分配行为的深入认识。本文通过改变流体相、熔体相的化学组成，开展了一系列锡在流体和花岗质熔体相间分配行为的实验研究。综合分析了锡在晶体-熔体-流体间的分配行为，并结合地质实际探讨与富碱侵入岩有关的锡成矿的物理化学条件和成矿机理。研究成果对深入认识与花岗岩有关锡矿的成矿机理、丰富和完善与花岗岩有关的锡成矿理论、为进一步探索与花岗岩有关的锡成矿规律提供重要的实验依据。此外，实验对进一步推动实验地球化学学科发展具有重要意义。 实验在中国科学院地球化学研究所矿床地球化学国家重点实验室的成矿实验室完成，主要实验设备为快速内冷（RQV）高压釜。实验的温度为850℃，压力100MPa、氧逸度接近NNO。实验首先采用人工合成硅酸盐凝胶的方法制成具有不同化学组成的花岗质熔体，使用分析纯化学试剂配制不同成分和不同浓度的溶液，分别作为实验初始固液相。主要开展了三方面的实验研究：1．熔体相组成不变，以改变流体相组成来观察锡的分配行为。这组实验固相初始物为过碱质富钾的硅酸盐，初始液相分别为NaCl、KCl、HCl、HF、去离子水溶液；2．流体相组成不变，改变熔体化学组成观察锡分配行为。初始液相选用低浓度的0.1mol/L HCl溶液，熔体相为具不同化学组成的凝胶（其中一组改变熔体碱质含量和铝饱和指数ASI、另一组改变熔体钠钾摩尔比值）；3．氟氯共存含水的花岗质岩浆体系中氟氯含量相对变化时锡分配行为。实验通过改变熔体相中氟含量和液相盐酸溶液的浓度来观察锡在含氟硅酸盐熔体和不同浓度盐酸溶液间的分配行为。氟主要以(NaF+KF)混合物的形式加入初始固相中。实验研究结果表明： 1．流体相络阴离子种类及含量对锡在流体-熔体相间的分配行为有着明显的影响。当流体相中络阴离子Cl－、F－含量增大时，有利于增大锡在流体-熔体相间的分配系数；尤其当流体为富氯的酸性流体时，锡在流体-熔体相间的分配系数随液相中HCl浓度的增大而增大并存在关系式logD Sn=2.0247×log[HCl]＋0.6717（[HCl]的单位为mol/L），锡在流体相中主要以二价锡氯配合物的形式迁移，锡倾向于分配进入富氯的酸性流体中。此外，富氯酸性流体与共存的熔体反应后，熔体中的碱质含量降低，铝饱和指数增大。 2．熔体化学组成对锡在熔体相/流体相的分配行为有着明显的影响。D Sn随着熔体中碱质含量增大而减小：D Sn=－0.0489×MAlk＋0.4516, R2=0.98（MAlk为熔体中Na2O+K2O摩尔含量），表明富碱质熔体有利于锡在熔体相中富集，从而可能为锡矿形成提供矿质来源。D Sn随熔体ASI值的增大而增大：D Sn=0.1886×ASI－0.1256, R2=0.99，即过铝质熔体相对有利于锡分配进入流体相中。过铝质熔体中碱质总量及其它组分相对不变的前提下，熔体钠钾摩尔比值越高D Sn越小：D Sn=－0.0314×RNa/K＋0.0483, R2=0.82（RNa/K为Na/K摩尔比值），富钠的熔体有利于锡分配进入熔体相，而富钾的熔体却相对有利于锡分配进入流体相中。 3．在氟氯共存花岗质岩浆体系中：①熔体相中氟含量对氯在流体-熔体相间的分配有着明显影响，熔体中氟含量降低有利于氯分配进入流体相。②熔体中氟含量大于约1 wt%后，D Sn小于0.1且变化不大，当液相富含HCl且熔体中氟含量从约1 wt%降低后，D Sn 迅速增大，即熔体中氟含量小于约1 wt%后锡倾向于分配进入富氯的酸性流体中。而富氟（F含量大于约1 wt%）的熔体有利于萃取锡并使锡在熔体相中富集。③熔体铝饱和指数ASI值越大，相应锡的分配系数越大；流体相中HCl浓度增大时，锡分配系数随之增大；当熔体为过铝质的花岗质熔体、流体富含HCl时有利于锡分配进入流体相。 分析总结与花岗岩有关的锡成矿特征和锡在不同晶体相和熔体相间的分配行为得出：壳源铝质、富碱、富挥发份、贫钙铁镁的岩浆在结晶分异演化过程中相对有利于锡在残余熔流体相中富集。因此，具有这些特征的岩浆结晶分异演化产生的晚期岩浆可富含锡，能为后期锡矿床的形成提供矿质来源。这种富锡富挥发份的岩浆在上侵过程中，当温度压力降低、岩浆水饱和度增大、硅含量增大、熔体相氟含量降低时，可分异出含氯富锡的成矿流体。 根据上述结论，分析了与湖南芙蓉锡矿床有着密切成因联系的骑田岭花岗岩的岩石化学特征、成岩成矿物理化学条件，得出芙蓉锡矿床成矿流体可由骑田岭晚期岩浆分异产生。 最后得出如下认识：1)当花岗质岩浆体系水不饱和、流体相络阴离子浓度低的情况下，锡倾向于分配进入熔体相中；2)水饱和富含挥发份的过铝、富钾的岩浆体系有利于锡分配进入流体相；3) 铝质、富钾、富挥发份的富碱侵入岩岩浆演化过程中可在有利的物理化学条件下分异出富锡的流体相，与芙蓉超大型锡矿床有成因联系的骑田岭富碱侵入岩体成岩过程中可分异出富锡的成矿流体。

Estabilidad del complejo azul de fosfomolibdeno : influencia de la acidez del medio y tiempo de desarrollo del color

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Quality of life and inflammation in exacerbations of bronchiectasis.

Patients with bronchiectasis often have impaired quality of life (QoL), which deteriorates with exacerbations. The aim of this study was to investigate changes in QoL and how these were influenced by changes in airway physiology and inflammation in patients with bronchiectasis before and after resolution of an exacerbation. Sputum induction and a QoL questionnaire were undertaken on the first day, day 14, and 4 weeks after completion of intravenous antibiotics (day 42). Eighteen patients (12 female) were recruited, median (IQ range) age of 54 (47–60) years. There was a trend towards an improvement in lung function from visit 1 to visit 2, but this was not statistically significant. C-reactive protein (CRP) [mean (SEM)] reduced between visit 1 and visit 2 [55.4 (21.5) vs 9.4 (3.1) mg/L, P = 0.03] but did not increase significantly on visit 3 [44.4 (32.9) mg/L, P = 0.27]. The median (interquartile range) sputum cell count (×106 cells/g of sputum) decreased from visit 1 to visit 2 [21.6 (11.8–37.6)–13.3 (6.7–22.9) × 106 cells/g, respectively, P = 0.008] and increased from visit 2 to visit 3 [26.3 (14.1–33.6) × 106 cells/g, P = 0.03]. All soluble markers of inflammation significantly reduced from visit 1 to visit 2 but increased on visit 3 with the exception of TNF-a. Regarding QoL, three of the four domains (dyspnoea, emotional, mastery) significantly improved from visit 1 to visit 2 but did not change between visit 2 and visit 3. The improvements in QoL scores could not be explained by the improvements in lung function or inflammatory markers.

The Kinetics of Semiconductor Photocatalysis in Activity-Indicator Films

The kinetics of dye reduction, in photocatalyst indicator ink films on self cleaning glass, is studied with respect to dye concentration. The water-based, photocatalyst indicator inks comprised a redox dye, D-ox, a sacrificial electron donor (glycerol) and a polymer, hydroxyethyl cellulose. The dyes used were: Resazurin (Rz), dichloroindo-phenol (DCIP) and methylene blue (MB), although the latter required acidification of the ink (0.01M HCl) to make it work effectively under ambient conditions. Under anaerobic conditions, the photoreduction of each of the dyes, in an otherwise identical ink formulation, on Activ (TM) self-cleaning glass is zero-order with respect to [D-ox]. Seven commercial samples of Rz, each in a typical ink formulation, were tested on the same piece of self-cleaning glass under aerobic conditions and produced a striking range (over 280%) of different apparent activities for the glass, when there should have been none. The underlying cause of this variation in assessed activity is shown to be due to the combination of a variation in the purity of the commercial samples and the zero-order nature of the kinetics of indicator dye reduction. The relevance of this work and the latter observation, in particular to future use of these films for the rapid assessment of the activities of new and established photocatalytic films, is briefly discussed.

Calibrated integrated backscatter and myocardial fibrosis in patients undergoing cardiac surgery.

Objective - The reported association between calibrated integrated backscatter (cIB) and myocardial fibrosis is based on study of patients with dilated or hypertrophic cardiomyopathy and extensive (mean 15–34%) fibrosis. Its association with lesser degrees of fibrosis is unknown. We examined the relationship between cIB and myocardial fibrosis in patients with coronary artery disease.

Methods - Myocardial histology was examined in left ventricular epicardial biopsies from 40 patients (29 men and 11 women) undergoing coronary artery bypass graft surgery, who had preoperative echocardiography with cIB measurement.

Results - Total fibrosis (picrosirius red staining) varied from 0.7% to 4%, and in contrast to previous reports, cIB showed weak inverse associations with total fibrosis (r=−0.32, p=0.047) and interstitial fibrosis (r=−0.34, p=0.03). However, cIB was not significantly associated with other histological parameters, including immunostaining for collagens I and III, the advanced glycation end product (AGE) Nε-(carboxymethyl)lysine (CML) and the receptor for AGEs (RAGE). When biomarkers were examined, cIB was weakly associated with log plasma levels of amino-terminal pro-B-type natriuretic peptide (r=0.34, p=0.03), creatinine (r=0.33, p=0.04) and glomerular filtration rate (r=−0.33, p=0.04), and was more strongly associated with log plasma levels of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) (r=0.44, p=0.01) and soluble RAGE (r=0.53, p=0.002).

Conclusions - Higher cIB was not a marker of increased myocardial fibrosis in patients with coronary artery disease, but was associated with higher plasma levels of sVEGFR-1 and soluble RAGE. The role of cIB as a non-invasive index of fibrosis in clinical studies of patients without extensive fibrosis is, therefore, questionable.

In vitro evaluation of fibrolytic enzymes as additives for maize (Zea mays L.) silage - III. Comparison of enzymes derived from psychrophilic, mesophilic or thermophilic sources

A completely randomised study was completed to examine the influence of fibrolytic enzymes derived from psychrophilic, (F), mesophilic, (L) or thermophilic (Ta) sources, applied at ensiling, on the chemical characteristics and in vitro rumen fermentation of maize silage, assessed using the Reading Pressure Technique (RPT). Treatments, all in triplicate, consisted of untreated maize forage or treated with preparations F, L, Ta or a mixture (1: 1, v/v) of F and L (FL), at two levels each, and ensiled for 210 days in plastic mini-silos. Addition of enzymes L decreased (P < 0.05) silage pH relative to the control, whereas enzyme Ta tended (P < 0.10) to reduce it. Preparations F, L and Ta tended to reduce (P < 0.10) the fibre contents of the silages, with effects being attributable to a decrease in the cellulose fraction. Starch contents were reduced (P < 0.05) in the treatments including enzyme F. End-point (96 h) gas production (GP) values did not differ among treatments, suggesting that enzymes did not change the total amount of fermentable substrate. However, consistent with the decrease in starch contents, adding enzyme F reduced (P < 0.05) GP at most incubation times. Addition of enzymes increased (P < 0.05) the initial (6 h) organic matter degradation (OMD) levels in all but one treatment (F), with increases of 14, 19, and 26% for preparations L, Ta, and FL, respectively, averaged across levels. Furthermore, the addition of enzymes increased (P < 0.05) the soluble OM losses, however, these increases did not fully account for the initial increase in OMD. The latter suggests that enzymes increased solubility and also altered silage structure, making it more amenable to degradation by ruminal microorganisms. As a result of the increase in OMD, without a concomitant increase in GP, the fermentation efficiency was greatly increased (P < 0.05) in enzyme treatments. Addition of enzymes to maize at ensiling, particularly those from the mesophilic and thermophilic sources used here, have the potential to increase the initial rate of silage OMD. (C) 2003 Elsevier B.V. All rights reserved.