Inhibitory effects of catechol accumulation on benzene biodegradation in Pseudomonas putida F1 cultures

The influence of benzene concentration on the specific growth rate (mu), CO(2) and metabolite production, and cellular energetic content (i.e., ATP content), during benzene biodegradation by Pseudomonas putida F1 was investigated. Within the concentration range tested (5-130mg benzene l(-1)) the mu, the specific CO(2) production, and the ATP content remained constant at 0.42-0.48h(-1), 1.86+/-0.21g CO(2) g(-1) biomass, and 5.3+/-0.4x10(-6)mol ATP g(-1) biomass, respectively. Catechol accumulated during process start-up at all tested concentrations. Catechol specific production increased with increasing benzene inlet concentrations. This confirms that the transformation of this intermediate was the limiting step during benzene degradation. It was shown that catechol inhibited both the conversion of benzene to catechol and its further transformation. In addition, catechol concentrations higher than 10mgl(-1) significantly decreased both benzene and catechol associated respiration, confirming the highly inhibitory effect of this intermediate. This inhibitory threshold concentration was approximately two orders of magnitude lower than the concentrations present in the culture medium during process start-up, suggesting that cellular activity was always far below its maximum. Thus, due to its toxic and inhibitory nature and its tendency to accumulate at high benzene loading, catechol must be carefully monitored during process operation.     

Real-time reverse transcription PCR analysis of trichloroethylene-regulated toluene dioxygenase expression in Pseudomonas putida F1

Toluene dioxygenase (tod) is a multicomponent enzyme system in Pseudomonas putida F1. Tod can mediate the degradation of Trichloroethylene (TCE), a widespread pollutant. In this study, we try to explore the TCE-regulated tod expression by using real-time qRT-PCR. The minimal culture media were supplemented with glucose, toluene, or a mixture of glucose/toluene respectively as carbon and energy sources. The TCE was injected into each medium after a 12-hour incubation period. The TCE injection severely affected bacterial growth when cultured with toluene or toluene/glucose mixtures. The cell density dropped 61 % for bacteria growing in toluene and 36 % for bacteria in the glucose/toluene mixture after TCE injection, but the TCE treatment had little effect on bacteria supplied with glucose alone. The decrease in cell number was caused by the cytotoxicity of the TCE metabolized by tod. The results from the real-time qRT-PCR revealed that TCE was capable of inducing tod expression in a toluene-dependent manner and that the tod expression level increased 50 times in toluene and 3 times in the toluene/glucose mixture after 6 hours of TCE treatment. Furthermore, validation of the rpoD gene as a reference gene for P. putida F1 was performed in this study, providing a valuable foundation for future studies to use real-time qRT-PCR in the analysis of the P. putida F1 strain.     

Real-time reverse transcription PCR analysis of trichloroethylene-regulated toluene dioxygenase expression in Pseudomonas putida F1

Toluene dioxygenase (tod) is a multicomponent enzyme system in Pseudomonas putida F1. Tod can mediate the degradation of Trichloroethylene (TCE), a widespread pollutant. In this study, we try to explore the TCE-regulated tod expression by using real-time qRT-PCR. The minimal culture media were supplemented with glucose, toluene, or a mixture of glucose/toluene respectively as carbon and energy sources. The TCE was injected into each medium after a 12-hour incubation period. The TCE injection severely affected bacterial growth when cultured with toluene or toluene/glucose mixtures. The cell density dropped 61 % for bacteria growing in toluene and 36 % for bacteria in the glucose/toluene mixture after TCE injection, but the TCE treatment had little effect on bacteria supplied with glucose alone. The decrease in cell number was caused by the cytotoxicity of the TCE metabolized by tod. The results from the real-time qRT-PCR revealed that TCE was capable of inducing tod expression in a toluene-dependent manner and that the tod expression level increased 50 times in toluene and 3 times in the toluene/glucose mixture after 6 hours of TCE treatment. Furthermore, validation of the rpoD gene as a reference gene for P. putida F1 was performed in this study, providing a valuable foundation for future studies to use real-time qRT-PCR in the analysis of the P. putida F1 strain.     

Cometabolic degradation kinetics of TCE and phenol by Pseudomonas putida

Modeling of cometabolic kinetics is important for better understanding of degradation reaction and in situ application of bio-remediation. In this study, a model incorporated cell growth and decay, loss of transformation activity, competitive inhibition between growth substrate and non-growth substrate and self-inhibition of non-growth substrate was proposed to simulate the degradation kinetics of phenol and trichloroethylene (TCE) by Pseudomonas putida. All the intrinsic parameters employed in this study were measured independently, and were then used for predicting the batch experimental data. The model predictions conformed well to the observed data at different phenol and TCE concentrations. At low TCE concentrations (<2 mg l(-1)), the models with or without self-inhibition of non-growth substrate both simulated the experimental data well. However, at higher TCE concentrations (>6 mg l(-1)), only the model considering self-inhibition can describe the experimental data, suggesting that a self-inhibition of TCE was present in the system. The proposed model was also employed in predicting the experimental data conducted in a repeated batch reactor, and good agreements were observed between model predictions and experimental data. The results also indicated that the biomass loss in the degradation of TCE below 2 mg l(-1) can be totally recovered in the absence of TCE for the next cycle, and it could be used for the next batch experiment for the degradation of phenol and TCE. However, for higher concentration of TCE (>6 mg l(-1)), the recovery of biomass may not be as good as that at lower TCE concentrations.     

Influence of dissolved oxygen on aggregation kinetics of citrate-coated silver nanoparticles

Aggregation, an important environmental behavior of silver nanoparticles (AgNPs) influences their bioavailability and cytotoxicity. The work studied the influence of dissolved oxygen (DO) or the redox potential on the stability of AgNPs in aqueous environments. This study employed time-resolved dynamic light scattering (TR-DLS) to investigate the aggregation kinetics of citrate-coated AgNPs. Our results demonstrated that when DO was present, the aggregation rates became much faster (e.g., 3-8 times) than those without DO. The hydrodynamic sizes of AgNPs had a linear growth within the initial 4-6 h and after the linear growth, the hydrodynamic sizes became random for AgNPs in the presence of DO, whereas in the absence of DO the hydrodynamic sizes grew smoothly and steadily. Furthermore, the effects of primary particles sizes (20, 40, and 80 nm) and initial concentrations (300 and 600 μg/L) of AgNPs on aggregation kinetics were also investigated.     

初级基质对降解菌Pseudomonasputida共代谢苯扎贝特的影响

通过对3,5-二硝基水杨酸（DNS）法测定还原糖含量各影响因素的筛选,优化确定了显色时间8min,稳定时间10min,最佳波长490nm下进行吸光度测定的检测方法;分析分别以葡萄糖和麦芽糖作为外加碳源时,降解菌Pseudo—monasputidaB-31的生长情况和共代谢降解典型药物苯扎贝特（BZF）的过程。结果表明,降解菌只有在外加碳源的条件下才可正常生长,而且其在葡萄糖环境中生长得更好;拟合得到的葡萄糖、麦芽糖和BZF代谢动力学结果显示,葡萄糖对BZF去除的促进作用更为明显,同时从葡萄糖培养基中降解菌所提取的酶比活力要高于麦芽糖培养基,分析原因可能是葡萄糖所诱导的降解菌关键酶活力更强,而且还可能会产生不同的蛋白质点位。     

DO在厌氧序批式生物膜反应器中对厌氧氨氧化反应启动的影响

考察了DO在厌氧序批式生物膜反应器(ASBBR)中对厌氧氨氧化反应启动过程的影响.结果表明,当进水采用高纯氮气进行除DO处理后进入ASBBR时,ASBBR很快以厌氧氨氧化反应为主,运行13 d后,NO-3-N生成量、NO-2-N去除量、NH+4-N去除量比开始围绕0.25∶1.30∶1.00上下小幅波动,运行100 d后的总氮容积去除负荷为1.560 kg/(m3·d);当进水不除DO处理进入ASBBR时,从运行的第57天开始,ASBBR内才表现出明显的厌氧氨氧化反应特性,运行到第73天时,NO-3-N生成量、NO-2-N去除量、NH+4-N去除量比开始围绕0.21∶1.20∶1.00上下小幅波动,运行的93～100 d,总氮容积去除负荷稳定在较高水平,最高可达1.090 kg/(m3·d);进水不除DO处理时,会使厌氧氨氧化反应启动迟缓;无纺布作为生物载体,具有较强的抗水力负荷和基质(NH+4-N、NO-2-N)负荷能力.     

四氢呋喃对贴沙河水pH、溶解氧及微生物的影响

四氢呋喃是一种应用非常广泛的工业有机溶剂和中间体,但因其高水溶性和难生物降解性,使得四氢呋喃极容易进入水体和土壤中,造成环境污染。由于水具有流动性,污染物易随水体扩散,因此考察四氢呋喃对于水质的影响更显紧迫。选择了杭州市饮用水源——贴沙河作为考察对象,测定不同浓度四氢呋喃引起的贴沙河水短期和长期pH、溶解氧及可培养微生物数量这3个重要水质指标的变化,研究四氢呋喃对水体可能造成的影响。结果经过统计分析发现,四氢呋喃的添加使得水体pH随其浓度增加而显著上升;与空白对照相比,四氢呋喃使水体中微生物数量显著下降,但在实验设定不同浓度之间差异性不显著;四氢呋喃对河水溶解氧的影响不显著。     

溶解氧对底泥扰动状态下水体中磷去除和固定的影响

以太湖梅梁湾底泥和上覆水为研究对象,通过实验室实验研究了底泥扰动状态下溶解氧水平（2～4mg／L、5～6mg／L、7～8mg／L）对上覆水中磷去除和固定的影响。结果表明,底泥扰动和溶解氧水平对上覆水中磷迁移有明显影响。扰动时间延长,溶解性磷酸盐（DIP）和溶解性总磷（DTP）均呈降低的趋势;但溶解氧水平提高,上覆水中DIP和DTP浓度有所增加。底泥扰动和溶解氧水平改变了悬浮物上不同形态磷的数量分布。随着溶解氧水平提高,NH4Cl-P（1～5d平均值）和Fe／Al—P（1～5d平均值）含量及其占总磷（Tot—P）的百分比均呈逐渐降低的趋势。另外,闭蓄态铁铝结合态磷（Fe／Al—P）占Fe／Al—P的比值从51．2％（2～4mg／L）增加至54．1％（7～8mg／L）。     

溶解氧对晚期垃圾渗滤液短程硝化及微生物群落结构变化的影响

以上海老港垃圾填埋场配套污水处理设施中的污泥为菌种源,在序批式活性污泥反应器(SBR)中对晚期垃圾渗滤液进行短程硝化处理,调节SBR中溶解氧浓度,考察溶解氧对渗滤液短程硝化的影响,分析不同溶解氧条件下污泥微生物群落结构的变化.结果表明,低溶解氧(0.2～0.5 mg/L)条件下,SBR可以获得较高的短程硝化效率,反应17h后,SBR内亚硝态氮/氨氮(质量比)为1.05,氨氮负荷可达到1.5 kg/(kg·d)(以每千克污泥悬浮固体每天承担的氨氮计),出水可以满足后续厌氧氨氧化处理的要求.从污泥变形梯度凝胶电泳(DGGE)图谱中可以看出,SBR微生物群落结构中主要优势种有uncultured Bacteroidetes bacterium、uncultured bacterium、uncultured Candidatus Amoebophilus sp.等.随着溶解氧含量的升高,SBR内微生物群落结构的多样性有所升高,但溶解氧对微生物群落结构影响有限.     

溶解氧对EBPR主流除磷及侧流磷回收性能的影响

采用交替厌氧/好氧(An/O)模式下运行的SBR,考察不同溶解氧(DO)浓度(1.0、0.5、0.1 mg·L−1)对同步侧流磷回收的强化生物除磷(enhanced biological phosphorus removal,EBPR)主流系统除磷及侧流磷回收性能的影响。结果表明,整个实验阶段主流系统对COD、${{\rm{NH}}_4^ + }$-N及TN的去除均能稳定达到《城镇污水处理厂污染物综合排放标准》一级A标准,其中TN因出水${\rm{NO}}_3^ - $-N浓度的降低而降低,故TN去除率升高。DO为1.0 mg·L−1和0.5 mg·L−1时对磷的去除率分别为99.0%和95.4%,主流系统出水磷达标率分别为96.0%和84.0%。而当DO浓度过低(0.1 mg·L−1)时,硝化与吸磷对有限电子受体的竞争及吸磷时间不足导致反应结束时系统内平均磷残留量达1.02 mg·L-1,除磷率降至87.2%。鉴于侧流磷回收是对主流系统的磷剥夺,会影响污泥的好氧吸磷能力,继而厌氧阶段释磷量因侧流提取降低。与此同时,DO为1.0 mg·L−1时,侧流磷回收率较其余2个工况高,且此工况下主流系统的厌氧释磷及好氧吸磷能力均最高,考虑到主流工艺的可靠运行及出水稳定性,认为DO=1.0 mg·L−1为最优工况。     

Effect of pH and temperature on the kinetics of odor oxidation using chlorine dioxide

Increasing public concerns over odors and air regulations in nonattainment zones necessitate the remediation of a wide range of volatile organic compounds (VOCs) generated in the poultry-rendering industry. Currently, wet scrubbers using oxidizing chemicals such as chlorine dioxide (ClO2) are utilized to treat VOCs. However, little information is available on the kinetics of ClO2 reaction with rendering air pollutants, limiting wet scrubber design and optimization. Kinetic analysis indicated that ClO2 does not react with hexanal and 2-methylbutanal regardless of pH and temperature and implied that aldehyde removal occurs primarily via mass transfer. Contrary to the aldehydes, ethanethiol or ethyl mercaptan (a model compound for methanethiol or methyl mercaptan) and dimethyl disulfide (DMDS) rapidly reacted with ClO2. The overall reaction was found to be second and third order for ethanethiol and DMDS, respectively. Moreover, an increase in pH from 3.6 to 5.1 exponentially increased the reaction rate of ethanethiol (e.g., k2 = 25-4200 L/mol/sec from pH 3.6 to 5.1) and significantly increased the reaction rate of DMDS if increased to pH 9 (k3 = 1.4 x 10(6) L2/mol2/sec). Thus, a small increase in pH could significantly improve wet scrubber operations for removal of odor-causing compounds. However, an increase in pH did not improve aldehyde removal. The results explain why aldehyde removal efficiencies are much lower than methanethiol and DMDS in wet scrubbers using ClO2.     

Effect of dissolved oxygen concentration on nitrite accumulation in nitrifying sequencing batch reactor.

A mathematical model based on Activated Sludge Model No. 3 (International Water Association, London) and laboratory-scale experiments were used to investigate ammonia conversion by nitrification in a sequencing batch reactor (SBR). The purpose of the study was to assess the effect of dissolved oxygen concentration on nitrite accumulation in the SBR. As the dissolved oxygen concentration in the SBR depends on the balance between oxygen consumption and oxygen transfer rates, ammonium conversion was measured for different air flowrate values to obtain different dissolved oxygen concentration profiles during the cycle. The ammonia concentration in the feeding medium was 500 mg ammonium as nitrogen (N-NH4(+))/L, and the maximum nitrite concentration achieved during a cycle was approximately 50 mg nitrite as nitrogen (N-NO2)/L. The air flow supplied to the reactor was identified as a suitable parameter to control nitrite accumulation in the SBR. This identification was carried out based on experimental results and simulation with a calibrated model. At a low value of the volumetric mass-transfer coefficient (kLa), the maximum nitrite concentration achieved during a cycle depends strongly on k(L)a, whereas, at a high value of k(L)a, the maximum nitrite concentration was practically independent of kL(a).     

溶解氧对氧化沟同步硝化反硝化脱氮比率的影响

微孔曝气变速氧化沟是一种新型的氧化沟。本研究通过批式实验,测定同步硝化反硝化(SND)溶解氧抑制系数KO,依此计算不同DO浓度下的SND比率,并与实际运行状况进行对比。结果表明:活性污泥的KO为0.7801 mg/L;当DO浓度分别为1.2、1.0和0.8 mg/L时,理论的SND比率分别为45.11%、47.57%和50.88%,而相同条件下氧化沟中实际SND比率分别为47.38%、52.75%和60.31%;同步硝化反硝化在微孔变速氧化沟中是一种重要的脱氮路径。     

基于溶解氧和缺氧时长调控的间歇曝气策略对短程硝化脱氮工艺的影响

短程硝化的实现可推动能源节约型脱氮工艺的应用。通过阐述间歇曝气策略实现短程硝化的机理,分析了应用间歇曝气策略实例中的运行参数,总结了DO协同缺氧时长分别在单独短程硝化工艺、短程硝化-反硝化(PN/D)工艺以及短程硝化-厌氧氨氧化(PN/A)工艺中的影响效果,如对功能菌活性和系统脱氮效率的影响;提出了以功能菌种、污泥存在形式等影响途径作为依据,基于DO协同缺氧时长的调控策略,并对各脱氮工艺中的运行参数进行优化,以期为各工艺系统实现最佳运行效果提供参考。     

微包埋恶臭假单胞菌复合填料制备及性能评价

填料是废气生物净化系统的核心组件,对净化性能有直接影响。以聚乙烯醇、海藻酸钠、腐熟植物纤维等为辅料,采用微包埋法制备出一种包埋恶臭假单胞菌复合填料,并将其装填于生物过滤塔中评价其对甲苯的净化性能。结果表明,制备的复合填料性能稳定、启动速度快、适宜微生物生长,对甲苯有较好的净化效果。生物过滤塔在空床停留时间47 s、进气负荷不高于42.00 g·(m3·h)-1的条件下,去除率可达90%以上。系统停运3 d和7 d,重新启动1 h后,去除率即可恢复至80%以上。动力学研究显示,与Michaelis-Menten模型相比,Haldane模型对使用该复合填料的生物净化过程拟合度较高。制备的复合填料理化性能好,对甲苯具有较高的净化效果,具有一定的应用前景。     

溶解氧对活性污泥合成可生物降解塑料-PHB的影响

聚-β-羟基丁酸酯（polyhydroxybutyrate,PHB）是一种可完全生物降解和具有良好生物相容性的高分子材料,许多情况下可作为传统塑料的替代品。以活性污泥微生物作为PHB合成菌,研究了动态底物投加方式下,溶解氧对污泥贮存PHB过程的影响。结果表明,PHB的贮存过程相当程度上取决于氧的提供。溶解氧浓度的提高明显加快了底物乙酸的吸收,进而导致更大比例的乙酸被活性污泥贮存为PHB。试验中,溶解氧浓度由饱和浓度的10%提高到70%,PHB的产率由0.36 C mmol/C mmol 提高到0.56 C mmol/C mmol,PHB的胞内含量也由26%提高到37%。试验证明溶解氧是控制活性污泥合成PHB工艺的重要因素。     

Comparison of degradation studies in a biosimulator by continuous cultivation of Pseudomonas and indigenous microorganisms with varied dissolved oxygen concentrations

The aim of this study was to compare the potential of a pure bacterial culture of Pseudomonas with the potential of an indigenous microorganism for malathion degradation by continuous cultivation using two different sets of conditions (with-culture: Pseudomonas, and without-culture: indigenous microorganisms) at varied dissolved oxygen (DO) concentrations (4.0 and 8.0 mg/L) in a biosimulator. The samples were analysed for pH, DO and COD (unfiltered). Gas chromatography (GC) revealed that almost 90% of malathion removal was achieved within ten hours of treatment in both studies of with-culture using 4.0 and 8.0 mg/L DO, whereas COD was considerably reduced during the treatment process and the removal efficiency was found to be above 90% in both conditions. The removal of COD was found to be in direct relation to retention time. However, the unfiltered COD and malathion removal efficiency was significantly influenced by DO. The percentage degradation of malathion using 4.0 mg/L DO, with-culture after 10 hours was 90.01%, whereas after 51 hours it was 99.03%. The without-culture studies showed percentage values which were 38.29% after 10 hours, whereas the corresponding value after 51 hours was 96.84%. Similarly, the percentage degradation of malathion using 8.0 mg/L DO, with-culture studies revealed that almost 89.40% malathion degradation was achieved after 10 hours, whereas it was 96.91% after 51 hours after inoculation of the culture. However, for the without-culture studies the value after 10 hours was 52.34%, whereas 96.86% malathion degradation was achieved after 51 hours without added culture. Although no significant variation in the pH was observed during the study the pH values increased gradually during the treatment process in all of the conditions. A critical evaluation of data presented revealed that the degradation potential of Pseudomonas was better when compared to the degradation potential of indigenous microorganisms.     

Mn-Ag/13X的焙烧温度对等离子体催化氧化吸附态甲苯的影响

采用等体积浸渍法制备一系列在不同温度下焙烧的Mn-Ag/13X分子筛催化剂,并用SEM、BET、XRD和XPS对催化剂进行表征。在低温等离子体反应器中,考察了不同焙烧温度制备的催化剂对甲苯的吸附和低温等离子体催化氧化甲苯的性能。研究结果表明,在对甲苯的吸附中,不同温度下焙烧的催化剂的吸附穿透时间依次为：600 ℃ > 500 ℃ > 400 ℃ > 300 ℃ > 700 ℃,600 ℃的Mn-Ag/13X催化剂比表面积最大,到达甲苯吸附穿透的时间最长;在低温等离子体催化氧化甲苯中,不同温度下焙烧的催化剂催化氧化所产生的COx浓度大小依次为：500 ℃ > 600 ℃ > 400 ℃ > 300 ℃,CO2选择性依次为：600 ℃ > 500 ℃ > 400 ℃ > 300 ℃,焙烧温度为500 ℃的Mn-Ag/13X催化剂的晶格氧多,产生的COx多,对甲苯的催化氧化活性高。     

Effect of dissolved oxygen on biological nutrient removal by denitrifying phosphorus-accumulating organisms in a continuous-flow system

A laboratory-scale continuous-flow system with an anaerobic/anoxic/aerobic configuration was set up to study the effect of oxygen in the internal recycle stream; of particular interest was its performance of denitrifying phosphorus-accumulating organisms (DPAOs). It was found that, by using a degas device, the dissolved oxygen in the nitrate recycle stream was effectively decreased from 0.1 +/- 0.02 to 0.01 +/- 0.01 mg/L. This provided a favorable condition for DPAOs to grow under an anoxic condition and thus be sustained successfully in the system. When the degas device was removed from the system, the dissolved oxygen concentration in the anoxic reactor increased to 0.1 +/- 0.02 mg/L. The proliferation of the denitrifying glycogen-accumulating organisms (DGAOs) population and deterioration of DPAOs performance was observed. The increased population of DGAO/GAOs, which competed for the carbon source with DPAO/ PAOs, resulted in a poor performance of biological phosphorus removal.