HPLC determination of chlorate metabolism in bovine ruminal fluid

Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO₃ ^?), nitrate (NO₃ ^?), and nitrite (NO₂ ^?) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R² values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO₃ ^? ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production.     

固定化SRB吸附乳酸钠的动力学及再生动力学研究

用聚乙烯醇包埋硫酸盐还原菌(SRB),探讨固定化SRB小球的动力学规律及再生动力学控制机理,同时利用膜扩散控制模型与粒内扩散控制模型,描述固定化SRB小球循环吸附乳酸钠的动力学过程,计算出不同条件下的膜扩散系数D/δ和粒内扩散系数D的值.通过对固定化SRB小球吸附乳酸钠的动力学和再生动力学研究,为固定化SRB小球的营养源吸附与再生工艺参数的确定提供理论依据.     

Towards green membranes: preparation of cellulose acetate ultrafiltration membranes using methyl lactate as a biosolvent

Ultrafiltration membranes were prepared using cellulose acetate (CA) as a polymer, LiCl and CaCl₂ as porogens and methyl-(S)-lactate as a solvent. CA, methyl lactate and the porogens used in this work are obtained from renewable resources; they are biodegradable, non-toxic and non-volatile organic compounds. Flat sheet ultrafiltration membranes were prepared by the phase inversion technique. A molecular weight cut-off between 15 and 35 kDa (polyethylene glycol) and pure water permeability between 13 and 177 litres h^? 1m^? 2 bar^? 1 were obtained. These parameters are in the ideal range for water treatment industry. Improvement of pollutant degree and ecotoxicity of the process was evaluated by ‘green’ metrics by the P (pollutants, persistent and bioaccumulative) and E (ecotoxicity) parameters. Both of these variables were recorded as zero using our method. This study represents a step ahead towards the production of ultrafiltration polymeric membranes by a ‘greener’ process than current methods.     

不同基质条件下透性处理对脱硫弧菌硫酸盐还原活性的影响

乙醇透性处理1株普通脱硫弧菌Desulfovibrio vulgaris Hildenborough(DvH)强化硫酸盐生物还原活性,研究不同基质条件下透性处理程度对其硫酸盐还原活性影响.当以H2为电子供体时,10%乙醇处理的DvH硫酸盐还原活性最强,其次为15%;当乙醇浓度>15%时,DvH硫酸盐还原活性显著降低.当以乳酸为电子供体时,最佳乙醇浓度为20%,其次为15%和10%,乙醇浓度达到25%时,DvH仍保持一定的还原活性.不同供体条件下DvH对透性处理程度的响应不同,是因为H2与乳酸在细胞内发生氧化的位置不同,从而胞内电子传递途径不同.确保供体与受体之间电子传递链的完整性是合理确定透性处理程度及透性技术应用的关键.     

五氯酚对HeLa细胞毒性及DNA损伤的研究

以人宫颈癌HeLa细胞为研究对象,运用MTT法检测PCP处理后HeLa细胞的增长抑制率;通过测定细胞培养液中乳酸脱氢酶(LDH)的漏出率和总超氧化物歧化酶(SOD)的活性,评价PCP的细胞毒性作用;彗星实验检测HeLa细胞经不同浓度PCP处理后的DNA损伤.结果表明,PCP对HeLa细胞的半数抑制浓度(IC50)为66.59μmol.L-1;HeLa细胞在12.5、25、50、100和200μmol.L-1 PCP染毒条件下,LDH的漏出率随着染毒时间的增加逐渐增大,具有明显的时间-效应关系,在12.25、17.5和25μmol.L-1 PCP染毒下,细胞培养液中SOD的活性随着染毒时间的增加逐渐下降,存在显著的时间-效应关系,低浓度PCP(25μmol.L-1)显著增加细胞培养液中LDH的漏出率以及PCP(12.25μmol.L-1)显著降低总SOD的活性;PCP(实验浓度为6.25、12.5、25和50μmol.L-1)不会导致HeLa细胞DNA损伤.因此SOD和LDH可作为评价低浓度PCP毒性效应的敏感性生物标志物.     

新型热电厂烟气脱硫剂的制备及中试试验

采用乙醇胺、乳酸及乙醇合成了乙醇胺乳酸盐,并将其与水复配制得含水量为15%的乙醇胺乳酸盐离子液体脱硫剂(ELIL脱硫剂),探讨了中试脱硫试验过程中脱硫剂的SO_2吸收性能及重复使用性能。试验结果表明:在长达72 h的吸收过程中,该脱硫剂的硫容(以SO_2计)与吸收时间呈一次函数关系;在硫容达到3.0%左右时,ELIL脱硫剂的黏度达到最大值;以w(SO_2)为0.69%的模拟烟道气连续中试运转72 h,尾气中的SO_2质量浓度远小于50 mg/cm~3,达到GB 13271—2014《锅炉大气污染物排放标准》的要求;使用5次后,ELIL脱硫剂的饱和硫容基本稳定在4.6%,重复使用性良好;随着重复使用次数的增加,SO_4~(2-)积累量逐次增加,可通过加入Ca(OH)_2除去SO_4~(2-),提高ELIL脱硫剂的脱硫性能。     

高价铬及双酚A在铁-乳酸体系中的同时光处理

研究了Fe(Ⅲ)-乳酸配合物体系同时对Cr(Ⅵ)的光还原及双酚A(BPA)的光氧化处理,考察了光源、初始pH值、Fe(Ⅲ)、乳酸盐、Cr(Ⅵ)及BPA初始浓度等因素对Cr(Ⅵ)及BPA光处理效率的影响。结果表明:光照条件下,铁-乳酸配合物能有效实现对六价铬及BPA的同时光处理。同一体系中,Cr(Ⅵ)的光还原快于BPA的光氧化,Fe(Ⅲ)初始浓度的增加可同时提高Cr(Ⅵ)的光还原效率和BPA的光氧化效率;Fe(Ⅲ)-乳酸盐配合物光解产生的Fe(Ⅱ)是Cr(Ⅵ)的主要还原剂,其次级光反应中产生的.OH是BPA的氧化剂。     

茅草添加与温度变化对餐厨垃圾厌氧水解产酸的影响简

比较了茅草添加在温度变化条件下对餐厨垃圾厌氧水解过程小分子有机酸产量的影响,提出一种新型餐厨垃圾的资源化方式。研究结果显示,餐厨垃圾在55℃条件下厌氧水解主要产物为乳酸,达到25.7 g/L,其干物质转化率可以达到32.1% （g TS）,而餐厨+茅草处理在同样条件下的乳酸产量为20.1 g/L,干物质转化率为25.1%。温度下降为37℃后继续进行的的厌氧水解,得到的主要产物是乙酸、丙酸和丁酸,餐厨处理和餐厨+茅草处理这两者的峰值分别为6.5、2.8、8.0和6.1 g/L、2.7 g/L和5.9 g/L。结果显示茅草添加可以在一定程度上调节水解产物的比例,而温度变化可以调控小分子有机酸的产量。本研究结果表明,厌氧水解是一种有潜力的小分子有机酸生产与餐厨垃圾资源化处理途径。     

固定化SRB小球吸附乳酸钠及处理Cd(Ⅱ)的研究

用聚乙烯醇(PVA)-硼酸包埋法对硫酸盐还原菌(SRB)进行固定, 考察加入PVA、SRB污泥、碾磨颗粒活性炭的量对其吸附乳酸钠的影响, 从而确定平衡参数, 进行吸附平衡分析.同时还考察Cd2 浓度、温度等因子对其处理Cd2 的影响.结果表明: 添加15%PVA, 6%碾磨颗粒活性炭, 40%SRB污泥后, 固定化小球的平衡时间为3.5 h, 平衡吸附量为6.1 mg/g,该吸附过程属于物理吸附;当Cd2 ≤900 mg/L时,其去除率均超过90%;且在100mg/L Cd2 ,pH 7.0,温度30 ℃时,Cd2 处理率更高达98.5%;而固定化SRB受初始pH和转速的影响不显著,受温度的影响稍显著.     

乳酸片球菌L-乳酸脱氢酶基因的克隆及在大肠杆菌中的表达

与其它微生物相比,用大肠杆菌进行发酵生产乳酸有许多优势,但大肠杆菌没有L乳酸脱氢酶基因,不能利用糖发酵生产L乳酸.本文采用PCR技术,以乳酸片球菌(Pediococcusacidilactici)基因组DNA为模板,克隆得到L乳酸脱氢酶(Llactatedehydrogenase)基因,将该基因的ORF连接到表达质粒pET22b( ),获得重组质粒pETldhL.将pETldhL质粒转化大肠杆菌BL21株,实现了ldhL基因的表达;对含有ldhL基因的重组菌株进行表达研究,在30℃以IPTG诱导8h后,SDSPAGE分析可见明显特异性条带,酶活力达到6.49u/mL,是野生菌酶活力(2.82u/mL)的2.3倍.对重组表达的L乳酸脱氢酶生物学特性研究显示,它们的最适反应温度为27～30℃,最适反应pH为5.0～5.3.图5参15