芽孢杆菌SeRB-2还原亚硒酸盐的动力学研究

微生物还原亚硒酸盐的动力学研究具有重要的现实意义,可以为Se(IV)污染场地的微生物修复设计提供理论依据。本文研究了兼性厌氧菌Bacillus sp.SeRB-2对亚硒酸钠的还原动力学。通过指数方程模型、对数方程模型和米氏方程模型的分析可知,Se(IV)的细菌还原符合一级反应动力学,还原反应主要集中在对数期和稳定生长前期,米氏方程模型能更好的反映细菌对亚硒酸盐的还原过程。通过对不同Se(IV)浓度下的米氏常数(Km)和最大反应速率(Vmax)的分析发现,当Se(IV)浓度较低时,Km值较小,Vmax值较大,这表明Se(IV)浓度越低,还原亚硒酸盐的酶与Se(IV)的结合能力越强,此时细菌对亚硒酸盐的还原速率越大、还原效率也越高。在本研究中,当Se(IV)浓度为1mmol/L时,其还原效率最高可达90%,能够有效去除或降低Se(IV)污染,说明该菌在Se(IV)污染场地的生物修复上具有应用潜力。     

温度对汞抑制土壤脲酶动力学影响研究

以不同施肥方式、不同有机质含量的草甸棕壤和黑土4个土样为对象,研究了不同温度条件下,汞(Hg)对土壤脲酶动力学特征的影响.结果表明,同一类型、有机质含量高的土壤脲酶活性、酶促最大反应速度(V_max)和V_max/K_m均高于有机质含量低的土壤,表明有机质对脲酶的吸附能力较强;黑土V_max和V_max/K_m值总体上大于草甸棕壤,但酶活性和米氏常数(K_m)值在不同土壤类型之间规律性较差,反映出酶活性由总酶量和酶-底物亲和力等因素共同决定;黑土K_m值大小与有机质含量相一致,而草甸棕壤则相反,表明有机质含量和施肥方式均会对K_m值产生影响;在最适温度以下,随温度升高,土壤的脲酶活性、V_max和V_max/K_m值均增加;Hg对土壤脲酶表现出典型的反竞争性抑制现象;Hg对脲酶活性的抑制作用及对K_m、V_max和V_max/K_m的负效应均随温度升高而有增加的趋势,揭示出土壤对脲酶的保护能力随温度升高而有所下降.     

六价铬还原细菌Bacillus cereus S5.4还原机理及酶学性质研究

从宝钢电镀污泥中分离得到1株六价铬还原细菌Bacillus cereus S5.4,在液体LB培养基中培养72　h完全还原2　mmol/L Cr⁶⁺.测定该菌株六价铬还原后细胞内外六价铬和总铬浓度,检测细胞各组分六价铬还原能力,并结合扫描电镜分析六价铬还原前后细胞形态的变化.结果表明,细菌的细胞壁膜能阻止六价铬进入细胞,是六价铬发生还原的主要场所,其通透性的改变将影响六价铬还原酶的作用;该菌株六价铬还原酶为非分泌型,在细菌细胞内侧发生作用.测定六价铬还原酶活性和稳定性：其最适温度范围25～37℃,最适pH 7,Cu2＋有增强六价铬还原酶活性的作用;在37℃,该菌株六价铬还原酶K_m为125.61 μmol/L,V_max为7.68 nmol/(min·mg).     

胶州湾围隔实验中溶解有机物三维荧光特征

利用三维荧光激发发射矩阵光谱法(EEMS),测定胶州湾围隔实验中不同营养盐条件下产生的溶解有机物的三维荧光特性.结果显示,浮游植物可产生类蛋白和类腐殖质荧光,类蛋白荧光峰由类酪氨酸(tyrosine-like)荧光峰和类色氨酸(tryptophan-like)荧光峰组成,主要位置为Ex_max/Em_max=270 nm/290～310 nm,Ex_max/Em_max=270～290 nm/320～350 nm的荧光峰强度比较弱;在Ex_max/Em_max=250～260 nm/380～480 nm(A峰)、Ex_max/Em_max=310～320 nm/380～420 nm(C峰)和Ex_max/Em_max=330～350 nm/420～480 nm(M峰)位置均出现零散的类腐殖质荧光峰,其中以A峰为主.类酪氨酸荧光强度明显高于类腐殖质荧光强度.浮游植物量降低时,类酪氨酸荧光强度与叶绿素a浓度呈明显的负相关.硅藻和甲藻产生的类酪氨酸和类色氨酸荧光强度之间具有较好的相关性,两者来源相似, 并且甲藻与硅藻相比能够产生更多的类蛋白荧光物质.不同环境下类腐殖质混合物的组分比例不同,甲藻生长环境下相对于硅藻具有较低的A/C比值.     

林可霉素生产废水的厌氧生物处理工艺

采用单相中温升流式厌氧污泥床(UASB)反应器厌氧生物工艺处理含有有毒难降解有机物的林可霉素生产废水.当进水COD 8000～14000 mg/L,HRT约10h时,COD容积负荷可达20～35kg/(m³·d),COD去除率为50%～55%.适时调整并维持较高的表面水力负荷[0.2～0.4 m³/(m²·h)]、较高的进水有机基质浓度(COD为2000～3000mg/L)和污泥COD负荷[0.2～0.5 kg/(kg·d)],并适当延长启动驯化时间可培养出沉降性好、污泥活性较高的颗粒污泥.废水厌氧生物降解动力学符合Monod方程,动力学常数V_max=1.3 d^-1,K_s=8133mg/L.废水中不可生物降解物质占总COD的比例约为30%,这是废水COD去除率偏低的重要因素.     

溴化十四烷基吡啶对膨润土吸附萘的增强效应及机理

研究了溴化十四烷基吡啶(MPB)对膨润土吸附萘的增强效应、机理及影响因素,试图为有机膨润土在污染环境修复中的应用提供新的技术路线.结果表明,MPB能显著增强膨润土对萘的吸附作用,增强效应及机理与MPB浓度有关.当MPB平衡浓度(X)在0～1/10CMC之间,MPB几乎全部被膨润土吸附,对萘产生分配作用,其表观分配系数(K_d^*)随MPB加入量的增大而急剧增大;当X在1/10CMC～ICMC之间,由于表面活性剂的吸附作用及其单体的增溶作用,K_d^*值则缓慢减小;当X大于1CMC,由于增加的表面活性剂主要起胶束增溶作用,K_d^*值则急剧减小.引入了标化表观分配系数(K_oc^*)探讨萘在表面活性剂-膨润土-水体系中的吸附机理,其倒数(1/K_oc^*)与X呈线性关系;由线性斜率和截距可求得K_oc、K_mn、K_mc参数.     

久效磷降解菌的分离及其酶促降解特性研究

从某农药厂废水处理池的污泥中分离到1株久效磷高效降解菌株M-1,经过对其形态特征、生理生化、以及16S rDNA序列分析,该菌株初步鉴定为Paracoccus sp..M-1能以久效磷作为唯一碳源生长,24 h对100 mg·L^-1久效磷的降解效率为92.47%.久效磷降解酶定域表达试验表明该酶为胞内酶,组成表达.久效磷酶促降解的最适反应pH为8.0,最适反应温度为25 ℃;其米氏常数（K_m）为0.29 μmol·mL^-1,最大降解速率(V_max)为682.12 μmol·(min·mg)^-1.久效磷降解酶热稳定性差,碱性条件下能够保持较高降解活性.     

取代联苯的定量结构活性相关及联合毒性研究

测定了18种取代联苯对大型蚤(Daphnia magna)24h的单一毒性(24h-EC₅₀)及其混合物联合毒性.对单一毒性进行了定量结构活性相关(QSAR)分析,建立了辛醇-水分配系数(lgK_ow)模型,理论线性溶剂化能相关(TLSER)模型及量子化学参数模型,表明量子化学参数模型能很好地预测取代联苯的单一毒性.混合物联合毒性研究表明,取代联苯的联合毒性机制为浓度相加效应,并且根据浓度相加预测了混合物半数抑制浓度(EC_50mix),预测值与实验值非常吻合.     

2,4-二硝基酚厌氧生物降解动力学研究

研究了间歇试验条件下,2,4-二硝基酚(2,4-DNP)与葡萄糖共基质时的厌氧降解动力学.结果表明:2,4-DNP与葡萄糖能同时被微生物降解;葡萄糖浓度高低对2,4-DNP的降解影响不大,而2,4-DNP的存在明显影响COD的降解.当2,4-DNP浓度<225 mg/L时,其比降解速率随浓度增大而增大,浓度为225 mg/L时比降解速率达到最大;由于底物抑制,当2,4-DNP浓度>225 mg/L时,其比降解速率呈下降趋势.选用Andrews非竞争性抑制模型描述2,4-DNP厌氧降解动力学,对实验数据进行非线性拟合,求得模型参数q_max、K_s和K_i分别为3.24 mg/(h·g)、196.23 mg/L和165.91mg/L,实验数据与该动力学方程拟合较好.     

广州市秋季PM2.5中重金属的污染水平与化学形态分析

采用消解法和连续提取法分析了广州市秋季PM_2.5样品中10种重金属元素的总量和化学形态,对广州市PM_2.5中重金属的污染水平和生物有效性进行了评价.结果表明,广州市PM_2.5和重金属污染非常严重,其中PM_2.5日浓度高达0.083 3～0.190 0 mg·m^-3,为1997年美国EPA相应标准的1.3～2.9倍.PM_2.5中Cd、Pb、Zn、Cu和Mo的富集因子K>10,是典型的污染元素;而Ni、Mn、Co和Fe的K值为1～10,除部分来自人为活动外,主要还是自然作用来源.化学形态分析结果显示,超过80％的Al和Fe分布在有机质、氧化物与硫化物结合态和残渣态,而大部分Zn、Pb、Cd 和Cu分布在可溶态、可交换态、碳酸盐态、可氧化态和可还原态.生物有效性系数(K)分析结果说明,PM_2.5中重金属的生物有效性相对强弱顺序为：Cd>Zn>Pb>Cu>Mn>Mo>Co>Ni>Fe>Al.其中Cd、Zn和Pb的K>0.8,为生物可利用性元素;Cu、Mn、Mo、Co和Ni的K值在0.5左右,为潜在生物可利用性元素;Fe和Al的K<0.2,为生物不可利用性元素.     

硫酸盐对两种硒形态处理下小麦硒吸收和转运的影响

为了揭示硫酸盐处理下小麦对亚硒酸盐和硒酸盐的吸收与转运规律,通过溶液培养,研究了不同浓度硫硒交互下小麦各部位的硒含量变化.结果表明,与无硫处理相比,0.1 mmol·L-1硫使小麦对硒酸盐的吸收潜力(Vmax值)和亲和力(1/Km值)分别降低了25.7%和90.8%,硫酸盐主要是通过降低小麦根系对硒酸盐的亲和力来缩小其与亚硒酸盐的吸收差异.小麦硒转移系数(TF值)随亚硒酸盐浓度的升高显著下降,降幅最高达35.3%,硫酸盐对其无显著影响;TF值随溶液中硒酸盐浓度的升高显著上升,最高增幅达53.8%,硫酸盐对其有显著促进作用.经亚硒酸盐处理后,无论施硫与否,小麦根部累积的硒均会随培养时间的延长显著向地上部运输;而经硒酸盐处理后,小麦根部累积的硒只在硫酸盐存在下才会随培养时间的延长显著运往地上部.富硒地区施用硫肥既可防止土壤硒的过度消耗,又可促进硒向可食部位的转移.     

Bioreduction of vanadium (V) in groundwater by autohydrogentrophic bacteria: Mechanisms and microorganisms

As one of the transition metals, vanadium (V) (V(V)) in trace amounts represents an essential element for normal cell growth, but becomes toxic when its concentration is above 1 mg/L. V(V) can alter cellular differentiation, gene expression, and other biochemical and metabolic phenomena. A feasible method to detoxify V(V) is to reduce it to V(IV), which precipitates and can be readily removed from the water. The bioreduction of V(V) in a contaminated groundwater was investigated using autohydrogentrophic bacteria and hydrogen gas as the electron donor. Compared with the previous organic donors, H₂ shows the advantages as an ideal electron donor, including nontoxicity and less production of excess biomass. V(V) was 95.5% removed by biochemical reduction when autohydrogentrophic bacteria and hydrogen were both present, and the reduced V(IV) precipitated, leading to total-V removal. Reduction kinetics could be described by a first-order model and were sensitive to pH and temperature, with the optimum ranges of pH 7.5–8.0 and 35–40°C, respectively. Phylogenetic analysis by clone library showed that the dominant species in the experiments with V(V) bioreduction belonged to the β-Proteobacteria. Previously known V(V)-reducing species were absent, suggesting that V(V) reduction was carried out by novel species. Their selective enrichment during V(V) bioreduction suggests that Rhodocyclus, a denitrifying bacterium, and Clostridium, a fermenter known to carry out metal reduction, were responsible for V(V) bioreduction.     

水稻对不同土壤中硒酸盐/亚硒酸盐的吸收和富集

通过土培试验研究了在3种类型土壤(红壤、黑土和灰钙土)上施用不同价态硒肥(Na2 SeO3或Na2 SeO4)条件下,水稻地上部硒含量的变化.结果表明,在水稻幼苗期,3种土壤上Se4+硒肥处理的水稻幼苗地上部硒含量高于Se6+硒肥处理.施用Se4+硒肥,红壤、黑土及灰钙土中水稻幼苗的硒含量分别为5.76、1.18和1.11 mg· kg-1,分别为对照的2.5、4.7和6.9倍;施用Se6+硒肥,红壤、黑土及灰钙土中水稻幼苗的硒含量分别为4.70、0.66和0.73 mg·kg-1.在水稻成熟期,施用Se4+硒肥后,红壤、黑土及灰钙土中水稻籽粒中硒含量分别由对照中的0.34、0.05和0.05 mg·kg-1增加到0.94、0.14和0.20 mg·kg-1;施用Se6+硒肥后,红壤、黑土及灰钙土中水稻籽粒中硒含量分别为1.13、0.12、0.16mg·kg-1.不同价态硒肥处理和土壤类型对水稻幼苗和成熟地上部硒含量都有显著影响.在pH值低的红壤上施用Se6+硒肥效果更好,而在pH值高的黑土和灰钙土上施用Se4+硒肥效果更好;从环境风险和硒对植物毒性的角度考虑,硒肥以亚硒酸盐的形式施用比较好.     

Two selenium tolerant Lysinibacillus sp. strains are capable of reducing selenite to elemental Se efficiently under aerobic conditions

Microbes play important roles in the transport and transformation of selenium (Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides, respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations (MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L. xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles (SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra- or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized SeNPs would have potential applications in agriculture, food, environment and medicine.     

Kinetic analysis and bacterium metabolization of α-pinene by a novel identified Pseudomonas sp. strain

Biodegradation has become a popular alternative remediation technology for its economic and ecological advantages. An aerobic bacterium (strain ZW) capable of degrading αup-pinene was isolated from a biofilter by a selective enrichment. Based on the 16S rRNA gene analysis and physiochemical properties, this strain was identified as Pseudomonas veronii. Under the optimized condition achieved by the response surface methodology (RSM), as well as pH 6.82, temperature 26.3\textcelsius and NaCl concentration 1.36%, almost 100% αup-pinene could be removed within 45 hr. Enzymatic biodegradation by the crude intracellular enzyme could be described well by the Michaelis-Menten model in which the maximum degradation rate V_max and the half-saturation constant K_m were calculated to be 0.431 mmol/(L. min) and 0.169 mmol/L, respectively. Activity assay of catechol suggested that the strain ZW possessed a catechol-1,2-dioxygenase and could decompose benzene-ring through ortho ring cleavage. Based on the identified intermediates by GC/MS, a new metabolic pathway was proposed, in which the final metabolites were some simpler organic and inorganic compounds. The present work demonstrated that the strain ZW would have a great application prospect for the remediation of αup-pinene-contaminated environment.     

Effect of bio-column composed of aged refuse on methane abatement – A novel configuration of biological oxidation in refuse landfill

An experimental bio-column composed of aged refuse was installed around the exhaust pipe as a new way to mitigate methane in refuse landfill.One of the objectives of this work was to assess the effect of aged refuse thickness in bio-column on reducing CH 4 emissions.Over the study period,methane oxidation was observed at various thicknesses,5 cm (small size),10 cm (middle size) and 15 cm (large size),representing one to three times of pipeline diameters.The middle and large size both showed over 90% methane conversion,and the highest methane conversion rate of above 95% occurred in the middle-size column cell.Michaelis-Menten equation addressed the methanotrophs diffusion in different layers of the bio-columns.Maximum methanotrophic activity (V max) measured at the three thicknesses ranged from 6.4 × 10 3 to 15.6 × 10 3 units,and the half-saturation value (K M) ranged from 0.85% to 1.67%.Both the highest V max and K M were observed at the middle-size of the bio-column,as well as the largest methanotrophs population,suggesting a significant efficiency of methane mitigation happened in the optimum zone with greatest affinity and methanotrophic bacteria activities.Therefore,bio-column is a potential style for methane abatement in landfill,and the aged refuse both naturally formed and artificially placed in the column plays a critical role in CH 4 emission.     

小白菜对外源硒酸盐和亚硒酸盐动态吸收的差异及其机制研究

通过盆栽试验和室内分析,研究了小白菜对不同含量的外源硒酸盐和亚硒酸盐动态吸收的差异,并通过土壤有效硒及生物量的动态变化探究其产生的原因,旨在为富硒作物的生产和硒污染土壤的植物修复提供理论依据.结果表明,硒酸盐和亚硒酸盐处理小白菜地上部分生物量间无显著差异.在小白菜的整个生长期间(8周),硒酸盐处理小白菜地上、地下部硒含量均随生长逐渐下降,而亚硒酸盐处理小白菜地上、地下部硒含量均随生长逐渐增大.硒酸盐处理地上部硒吸收量显著高于地下部,而亚硒酸盐处理地下部硒吸收量显著高于地上部;且在整个生长过程中硒酸盐处理小白菜硒吸收量是亚硒酸盐处理的2～60倍之多,导致硒酸盐处理土壤中有效硒含量随着小白菜的生长迅速下降,而亚硒酸盐处理土壤中有效硒含量随小白菜的生长略有下降.统计分析表明,硒酸盐处理小白菜体内硒含量与土壤有效硒含量呈显著正相关,地上、地下硒含量与土壤有效硒的相关系数分别为0.901和0.864,而亚硒酸盐处理两者相关性不显著.综合小白菜硒含量和土壤有效硒随生长变化的结果可以得出,小白菜对硒酸盐和亚硒酸盐动态吸收的差异是小白菜对不同价态硒吸收能力和土壤供硒能力综合作用的结果.     

硒酸钠和亚硒酸钠对长春花细胞悬浮生长的影响

研究了硒化合物对长春花(C.roseus)细胞悬浮生长的影响.在pH5.5培养介质中,当Se(Ⅵ)>0.5ppm或Se(Ⅳ)>0.6ppm时,将抑制C.roseus细胞悬浮生长,其致死浓度分别是100ppm Se(Ⅵ)和2.0ppm Se(Ⅳ).C.roseus对硒化合物有效强的富集作用.硒化合物的毒性和培养介质的pH值有关.在本试验条件下,硒酸钠和亚硒酸钠对Hg²⁺无拮抗作用.     

硒酸钠和亚硒酸钠对长春花细胞悬浮生长的影响

研究了硒化合物对长春花(C.roseus)细胞悬浮生长的影响.在pH5.5培养介质中,当Se(Ⅵ)>0.5ppm或Se(Ⅳ)>0.6ppm时,将抑制C.roseus细胞悬浮生长,其致死浓度分别是100ppm Se(Ⅵ)和2.0ppm Se(Ⅳ).C.roseus对硒化合物有效强的富集作用.硒化合物的毒性和培养介质的pH值有关.在本试验条件下,硒酸钠和亚硒酸钠对Hg~(2+)无拮抗作用.     

电子供体对地下水中高氯酸盐生物去除的影响研究

通过静态实验,考察了电子供体类型及用量对厌氧条件下微生物去除地下水中高氯酸盐的影响.结果表明,电子供体醋酸盐和H₂的加入,可以明显提高ClO₄^-的去除率,驯化后的微生物去除ClO₄^-的速率比未加入电子供体时提高约1.4~3倍.Monod动态模型能很好地拟合两种电子供体环境下ClO₄^-的微生物去除过程,分别以醋酸盐和H₂作为电子供体时,基质半饱和常数K_s为12.6 mg·L^-1和2.2 mg·L^-1,最大比基质消耗速率V_m为0.45 d^-1和0.08 d^-1.动力学参数表明,本实验条件下,异养型混合菌去除ClO₄^-的效果明显优于自养型混合菌;在少数受高浓度ClO₄^-污染的地下水环境中,为了提高ClO₄^-的去除速率只有通过增加菌体浓度或提高微生物酶的活性来实现.随着电子供体醋酸盐用量增加,ClO₄^-的(比)消耗速率逐渐增大.当初始CH₃COO^-与ClO₄^-的比例为3.80 mg(COD)/mg(ClO₄^-)时,比消耗速率v最大(0.27 d^-1).