双介质低温等离子体反应器工作参数优化及空气放电光谱分析

为研究工作参数对双介质低温等离子体反应器性能的影响,建立了双介质阻挡放电型低温等离子体反应器试验系统,观察空气放电产生的NO、NO2体积分数随放电频率、放电电压峰-峰值及空气流量等因素的变化。结果表明:不同放电频率时,双介质低温等离子体反应器气体放电反应机理不同;放电频率为7 k Hz时,NO、NO2均随放电电压峰-峰值线性增长;放电频率为8 k Hz时,随着放电电压峰-峰值的增大,NO先不变后增长,NO2线性增长;放电频率为9 k Hz时,随着放电电压峰-峰值的增大,NO始终维持在较低水平,NO2先不变后增长;NO、NO2体积分数随空气流量的增大而减小,不同空气流量时,NOx总体变化规律不会改变;双介质低温等离子体反应器放电频率为9 k Hz,放电电压峰-峰值为9~23 k V时,可产生较多的活性物质,同时避免大量副产物的生成。该研究可为利用NTP技术降低柴油机排放污染物提供参考。     

Simulation of transport through soil of E. coli derived from livestock slurry using the macro model

Abstract. Leaching of faecal coliforms to rivers, lakes and groundwater following the spreading of animal slurry on land is of environmental and public health concern. A two-stage approach was adopted to modelling the transport processes by which Escherichia coli passes through the soil to receiving waters via field drains. First, parameter values were selected for the dual-porosity contaminant transport model macro to simulate through-soil flows, sorption and die-off of E. coli . These simulations reproduced experimental measurements showing rapid flows of the microorganisms to field drains after slurry spreading, which could be explained in terms of macropore flow in which trapping of colloids such as E. coli does not take place. Second, a series of predictive simulations was carried out to test the influence of soil and weather conditions on E. coli losses. These showed that losses are strongly influenced by soil wetness conditions at the time of spreading, and to a lesser degree by rainfall occurring soon after spreading. Selection of spreading 'workdays' with particular weather and soil wetness conditions is beneficial, which indicates opportunities for substantial reductions in the environmental risks of water pollution by E. coli and other faecal microorganisms.     

壳聚糖澄清芦柑果汁工艺条件的优化

为了制备稳定的澄清芦柑果汁,该文基于Box-Behnken试验设计,探讨了壳聚糖浓度、澄清温度、澄清时间对果汁澄清度的影响;建立了二次多项式回归模型,分析模型的有效性与因子间的交互作用,并对壳聚糖澄清芦柑果汁的工艺参数进行了优化。结果表明：壳聚糖澄清芦柑果汁的最佳工艺参数为：壳聚糖浓度0.80 g/L、温度59℃和时间71 min。在此最佳工艺条件下果汁透光率达到97.8%,且试验结果与模型预测值（98.3%）相吻合,所得回归模型拟合情况良好（R2=0.9886）,达到设计要求。进一步对经壳聚糖澄清后的芦柑果汁的相关指标进行测定,发现果汁中可溶性固形物、维生素 C 及总酸含量依次从11.30±0.15%、31.33±3.25 mg/100mL、0.71±0.00 g/100mL略降为9.50±0.25%、21.8±5.28 mg/100mL、0.51±0 g/100mL,而总酚、果胶、蛋白质质量浓度依次从990.3±8.02 mg/L、366±4.70μg/mL、595.53±20.62μg/mL减少为557.87±4.67 mg/L、186.24±44.32μg/mL、26.42±0.30μg/mL 有较明显下降,但澄清后的果汁非生物稳定性很好。该试验用响应面法优选出的澄清工艺合理可行,为芦柑果汁深加工及果汁产品开发提供了理论依据。     

Simulating transport of E. coli derived from faeces of grazing livestock using the macro model

Abstract. Coliforms such as Escherichia coli and E. coli O157 are present in faeces deposited on the ground by grazing livestock, which gives rise to environmental concerns about the consequences of their transport in soil water draining to rivers, lakes, groundwater, water supplies and bathing waters. Following a similar study in relation to slurry spreading (Soil Use and Management 2003; 19, 321–330), a two‐stage approach was adopted to using the dual‐porosity contaminant transport model macro to simulate processes by which E. coli microorganisms from grazing livestock (sheep) pass through the soil to receiving waters via field drains. First, model parameter values were selected to reproduce experimental measurements showing rapid flows of the organisms by macropore flow without trapping in smaller pores. However, because of the large number of parameters and likely experimental errors, the set of values chosen, although plausible, is not necessarily unique and so any predictions should be considered provisional pending validation. Second, a series of predictive simulations was carried out to test the influence of soil and weather conditions on losses to field drains during grazing. These showed that E. coli losses were influenced almost entirely by the soil water content at the time of grazing, rising to a high level during grazing in wet conditions, but low or zero under dry conditions. In contrast, rainfall at the time of grazing had almost no consistent effect, other than large losses on the occasional days with over 20 mm of rain. Overall losses for a period of grazing were generally small during summer, but rose to a high level if grazing continued into autumn, due to the increase in soil water content. This demonstrates that there would probably be substantial reductions in the environmental risks of water pollution by E. coli and other faecal microorganisms if continuous grazing were stopped around early September and replaced by grazing on dry days only.     

Sherlock MIS系统鉴定土壤中大肠杆菌O157∶H7的研究

<正>污水灌溉和人畜粪肥施用一直是国内外农业中有机废弃物资源化利用的重要途径,这种现象在我国尤为普遍。然而,生活污水含有大量细菌,工业和医院废水更是富含各种病原体,污泥、垃圾和粪肥均可能携带大量病原微生物和寄生虫卵。显而易见的是,这些有害生物种群可随污水灌溉和粪肥施用进入环境中,并通过污染土壤、水源、大气和农畜产品等途径传播或"引燃"疫情的爆发,从而对     

重组大肠杆菌表达降氰酶的诱导条件优化

采用积分光密度法对产碱杆菌（Alcaligenes sp.）降氰酶基因在大肠杆菌中的高效表达进行了诱导条件优化,以工程菌BL21（DE3）-pET28a-cdE的诱导表达条件进行优化,以提高目的蛋白的产量和活性。结果显示,重组菌表达降氰酶的最佳诱导条件为温度28℃,初始菌体浓度OD600值为0.6,IPTG浓度为0.8mmol/L,诱导时间12h。研究发现,诱导剂的添加浓度对外源蛋白的表达水平具有显著影响,使用终浓度为0.8mmol/L的IPTG,诱导表达12h,降氰酶蛋白收率达到143.27mg/L,比活力达到11560 U/mg。与不添加诱导剂相比,重组蛋白的收率和比活力分别提高了64倍和9倍。     

蚯蚓粪中乳酸菌的分离及其在大肠杆菌O157：H7中的抗菌活性

本研究利用SL培养基从蚯蚓粪中分离到54株具有产酸性能的菌株,并以E.coli O157：H7（EDL933株）作为指示菌株,采用点种法检测分离菌株的抑菌活性。结果表明其中6个菌株对指示菌具有拮抗作用,通过形态特征,结合16S rDNA序列分析,初步鉴定该6个菌株分别为食物魏斯特菌（Listeria welshimeri）、乳酸片球菌（Pediococcus acidilactici）、短乳杆菌（Lactobacillus brevis）和格氏乳球菌（Lactococcus garvieae）。分离到的乳酸菌对E.coli O157：H7（EDL933株）具有显著的抑制作用,发酵温度和初始pH值影响发酵液的抑菌作用,优化环境因子可以促进拮抗菌对E.coli O157：H7的抑制作用。本研究为进一步分离抗菌产物用于人畜共患病的预防和治疗提供了理论依据。     

均匀设计在枇杷ISSR-PCR反应体系优化中的应用

本实验通过U255（5^4）均匀设计实验研究,对枇杷ISSR—PCR分子标记体系中模板DNA、dNTPs、TaqDNA聚合酶、Mg^2＋、引物5个组分的浓度进行优化。获得25μL反应体系中各成分的适宜浓度或用量分别是：模板DNA为10ng、dNTPs为0．5mmol／L、TaqDNA聚合酶为1U、Mg^2＋为2．5mmol／L,引物为0．4μmol／L。与单因素梯度优化体系相比,操作简便,简化了实验步骤,获得的实验结果可靠,从100条ISSR引物中筛选出27条扩增良好的引物,并获得了这些引物的最佳退火温度,经琼脂糖凝胶电泳获得了清晰的图谱。这一优化体系的建立为进一步利用ISSR标记技术进行枇杷种质鉴定及遗传多样性分析提供了一个标准化程序。     

Effect of CO2 enrichment on fruit growth and quality in Japanese pear (Pyrus serotina Reheder cv. Kosui)

Six year-old Japanese pear (Pyrus seratina Reheder cv. Kosui) trees grafted on P. serotina cv. Nihonyamanashi were grown in containers filled with Granite Regosol under glasshouse conditions. At different stages of fruit growth, pear trees were exposed to an elevated CO₂ concentration (130 Pa CO₂ ) along with a control (35 Pa CO₂). For one group of plants, CO₂ enrichment was applied for 79 d from 52 d after full bloom (DAB) to fruit maturity (long-term CO₂ enrichment) and for another group the same treatment was applied for 35 d from 96 DAB to fruit maturity (short-term CO₂ enrichment). The effects of the elevated CO₂ concentration on vegetative growth, mineral contents, and fruit production and quality were examined. Long-term CO₂ enrichment enhanced vegetative growth, without any significant effect on the mineral contents in either flower bud or fruit except for a remarkable increase in the K content. Long-term CO₂ enrichment increased the fruit size and fresh weight, but had no significant effect on the fruit quality. On the other hand, the short-term CO₂ enrichment did not induce any significant change in the fruit size but increased the fruit sugar concentration. Along with the reduction of the sorbitol concentration in fruit, the fructose and sucrose concentrations increased and these changes occurred earlier at elevated CO₂ than at ambient CO₂ concentrations. From these results, we concluded that the effect of CO₂ enrichment on fruit growth varies depending upon the growth stages of fruit: during the initial and fruitlet stages when fruit expansion occurs, CO₂ enrichment increases the fruit size, whereas, during maturation when fruit expansion has slowed down and sugar accumulation in fruit is active, it increases the fruit sugar concentration.