Synthesis of Poly(β-hydroxybutyrate) in Simulated Microgravity: An Investigation of Aeration Profiles in Shake Flask and Bioreactor

The microbial strain Azotobacter vinelandii UWD was grown under conditions of simulated microgravity in the National Aeronautics and Space Administration (NASA) Bioreactor. Bacterial growth in simulated microgravity differed significantly from that observed in conventional shake flask experiments: Cells tended to grow in a cluster-like pattern and polymer production started immediately after exposing them to conditions of simulated microgravity, and no lag time was observed. It was imperative to differentiate between the effects derived from microgravity and those imposed by the altered oxygen supply in the bioreactor. Aeration conditions were studied in both reactor types and a gas supply profile was developed for the bioreactor. This supply profile allowed for similar amounts of dissolved oxygen in the bioreactor and the shake flask in the initial stage of the fermentation and, therefore, for an evaluation of the effects of microgravity on biopolyester-producing bacteria. Since the optical density that is conventionally used as a measure for the cell growth could not be used due to the cluster-like growth pattern of the cells, it was determined that bacterial growth behavior in the bioreactor can be monitored through glucose or oxygen consumption.     

Quantification of Polymerisation Processes During The Oxidative Degradation of 14C-Labelled Chlorophenols

In experiments employing the lignocellulose-decaying basidiomycetes Trametes versicolor and Stropharia rugosoannulata degrading uniformly¹⁴C-labelled 2,4-dichlorophenol and pentachlorophenol, acombination of size exclusion chromatography (SEC),fractionation, and -scintillation counting wasapplied to quantify polymerisation products formed duringchlorophenol degradation. Time-dependent mass balances weregenerated by analysis of ¹⁴C in polymerisation products,CO₂, as well as monomer non-polar and polar metabolites.Approximately 30% of the chlorophenols were found to bepolymerised. A major fraction of the polymerised productscorresponded to a molecular weight range from 0.24 – 40 kDa.Only a minor fraction could be attributed to a molecularweight >40 kDa. This method proved to be useful inquantification of polymerisation products and kinetics of thepolymerisation processes, whereas UV/Vis detection ofpolymerisation products separated by SEC led to false positiveresults. The SEC-¹⁴C method could also be applied forother complex processes where polymerisation ordepolymerisation occurs (humification, degradation oflignocellulose, formation of bound residues from xenobioticssuch as polycyclic aromatic hydrocarbons or 2,4,6-trinitrotoluene) and where spectrophotometric determinationsare difficult or impossible.     

用MnSO_4作催化剂测定废水中的COD

介绍了用 Mn SO4代替 Ag2 SO4作催化剂测定废水中 COD的方法。该方法可降低分析成本 ,且使回流时间缩短为 30 m in,方法的变异系数、回收率分别为 0 .6 5 %和 96 .8%～10 0 .8%     

生物膜及其各种组分对4-氯酚化合物的吸附特征

对4-氯酚化合物在生物膜不同组分上的吸附行为的实验中,生物膜不同组分包括生长有生物膜外壳的模拟水体悬浮颗粒物(高岭土)、细菌细胞、胞外多糖、高岭土及有胞外多糖存在时的高岭土.在所设计的这5种吸附体系中,前4种吸附较符合Langmuir和Freundlich等温吸附方式.在室温25℃,pH值为6.1的吸附条件下,细菌细胞和胞外多糖作为生物吸附物质,对4-氯酚的吸附明显地大于高岭土;高岭土外的生物膜外壳影响对4-氯酚的吸附,生长有生物膜外壳的高岭土对4-氯酚的吸附量高于单独高岭土体系.     

新显色试剂的合成及在环境监测中的应用研究

合成了一种新三氮烯类显色剂--6-甲氧基苯并噻唑重氮氨基-2,6-二溴-4-羧基苯(简称MBTDABPCP),并研究了其与镉的显色反应.拟定了在SDS存在的Na₂₄₇-HCl缓冲溶液(pH为8.5)中,测定镉的新方法.可用于废水中微量镉的测定.      

放牧对内蒙古草原温室气体排放的影响

静态箱-气相色谱法用于测定内蒙古典型草原温室气体排放.禁牧草原及放牧草原吸收CH₄、排放N₂O和CO₂各自有其相对固定的季节变化形式,草原和大气交换温室气体通量的季节变化形式主要受年度气候变化所控制,而土壤、植被类型、降雨量等禁牧因素和放牧强度等人为因素仅影响排放强度.与禁牧草原相比,自由放牧降低了羊草草原对CH4的吸收和对N₂O的排放,但大大增加了CO₂的排放量.随着放牧强度的增加,草原温室气体排放强度呈线性迅速增长.     

环境因子对长江口潮滩沉积物中NH+4的释放影响

以长江口潮滩沉积物湿样进行模拟实验,研究盐度、pH和温度等环境因子对沉积物中NH₄+释放的影响.结果表明,随着盐度和温度的上升,沉积物中NH₄+释放量都显著增加;由于潮滩沉积物缓冲性能较好,pH的影响不太明显.此外,NH₄+的释放与沉积物类型有关,沙性物质含量高的低潮滩沉积物NH₄+的释放量明显低于沙性物质低的高、中潮滩沉积物.      

土壤无机离子在非均匀电场作用下的迁移

研究了非均匀电场对不饱和沙壤土中的NO₃^-和SO₄^2-的迁移特征,揭示利用非均匀电场向土壤中注入营养物和电子受体的特性.结果表明,非均匀电场能有效地增强土壤中NO₃^-和SO₄^2-的移动性,在1.0V/cm电压梯度下不饱和沙壤土中NO₃^-和SO₄^2-的电迁移速率分别高达22.0,16.5cm/d;在非均匀电场中无机离子主要通过场强较大的区域迁移;切换电场极性可以方便地控制土壤中NO₃^-和SO₄^2-的运移,同时能促使NO3-转化为NO₂^-.利用非均匀电场的迁移和富集效应,可以有效地向土壤中注入无机离子或者将污染离子从土壤中分离出来.     

北京市大气甲醛浓度研究

分别于2006年7, 9, 12月和2007年3月采用2, 4-二硝基苯肼(DNPH)高效液相色谱法测定了北京市大气中的φ(甲醛).结果表明:在观测期间,春、夏、秋、冬各季φ(甲醛)的平均值分别为7.56×10-9, 12.70×10-9和 7.24×10-9,3.34×10-9;夏季φ(甲醛)明显高于其他3个季节, 春、秋φ(甲醛)平均值非常接近, 冬季φ(甲醛)最低;夏季φ(甲醛)与 φ(O₃), 温度,UVB的日变化表现出良好的一致性,均在12:00—15:00出现高值;夏季φ(甲醛)主要受光化学氧化过程的控制和影响; 降水对大气甲醛有明显的清除作用.      

SO2-4/TiO2表面的酸性对其光催化性能的影响

采用Na2CO3溶液将SO2-4/TiO2表面的SO2-4洗脱下来,用热重(TG)、NH3程序升温脱附(NH3-TPD)和吡啶吸附的红外光谱等手段,分析洗脱前后SO2-4/TiO2表面的酸量和酸类型的变化;在相同晶型、结晶度和吸光特性条件下,考察了SO2-4/TiO2表面的酸性对Cr(Ⅵ)光催化还原效率的影响.结果表明:SO2-4/TiO2表面同时存在Lewis酸位和Bronsted酸位,通过Na2CO3溶液降低SO2-4/TiO2表面的酸量并去除Bronsted酸位后,其对Cr(Ⅵ)的光催化活性显著降低.