自养条件下小球藻净化氮磷能力的研究

研究了在自养条件下,小球藻净化氮、磷的能力。实验结果表明,小球藻对氮、磷的吸收在开始的前12h内速度比较快,利用率达70％和60％左右;吸收氮、磷2d,利用率可分别达到75％和62％。低浓度的氮、磷组合有利于小球藻对氮的吸收,在磷浓度50～100mg／l范围内可以有效地吸收磷,吸收率接近60％。升高温度有利于小球藻对磷、氮的吸收。     

氮磷浓度对藻-溞-草间相互作用的影响

为了解氮磷浓度对生物操纵效果的影响, 以小球藻、大型溞和金鱼藻分别作为浮游植物、浮游动物和大型沉水植物的代表, 建立了它们之间相互作用的水生微宇宙模型。研究了在25℃、2000—3000 lx 的温度和光照下, 不同氮磷浓度对三者生长的影响。结果表明: 两者共培养时, 在高氮(10.5 mg/L)条件下, 磷浓度小于0.1 mg/L 对大型溞繁殖和金鱼藻的生长有利; 磷浓度介于0.1—2 mg/L 时小球藻呈大暴发趋势, 而金鱼藻的生长则明显受抑制。在低氮(0.5 mg/L)条件下, 磷浓度不大于0.5 mg/L, 大型溞对小球藻有较好的抑制作用, 金鱼藻与小球藻无显著互抑现象; 磷浓度增大为2 mg/L 时, 小球藻对金鱼藻生长产生明显抑制。在0.05—2 mg/L 的磷浓度范围及高氮和低氮条件下三者共培养时, 大型溞数量及金鱼藻生物量均不同程度的升高,且小球藻数量得到了有效抑制, 以磷浓度为0.1—0.5 mg/L 时效果最佳; N/P 比值对藻、溞、草间的相互作用有重要影响, 在藻-溞系统中, 大型沉水植物的加入可以大大提高控藻效果, 减小N/P 比值波动带来的不利影响。与低氮情况相比, 高氮条件对金鱼藻、大型溞及小球藻的增长均存在一定抑制作用。磷浓度为0.5 mg/L时的水体氮磷去除效果好于其他磷浓度梯度。       

普通小球藻对养殖污水脱氮除磷的效果研究

随着我国养殖业的不断发展,养殖污水排放量的日益增加,养殖污水的高氮、磷含量导致水体富营养化问题日趋严重。小球藻是光能自养生物,能有效同化氮、磷,使污水中的氮、磷减少。本研究通过在实验室模拟不同氮、磷含量的养殖污水环境,分析小球藻对氮、磷的去除效果;在此基础上,用小球藻处理某养殖场污水;并联合膨润土与小球藻,探究两者脱氮除磷的协同作用能力及膨润土对小球藻细胞沉降的效果。结果表明,小球藻对模拟污水的氨氮去除率可达80%,对磷酸根的最高去除率接近100%;对养殖污水中的氮、磷也有一定的去除效果;但养殖污水成分复杂,小球藻的生长被抑制。膨润土与小球藻的结合,能够提高污水中的氮磷去除率并帮助藻细胞快速沉降,为污水处理后藻细胞的收集处理提供了有效方法。     

营养盐因子对细基江蓠繁枝变种氮、磷吸收速率的影响

在实验室条件下,研究了营养盐因子对细基江蓠繁枝变种的氮、磷吸收速率的影响。分别进行了营养盐浓度与温度双因子试验,氮磷比与荧 浓度双因子试验肽不同化合态氮比例单因子试验。（1）氮、磷的吸收速率随营养盐浓度的升高而增大,氮的吸收速率在21℃,总氮浓度为100μmol/L时最大,达2.58μmol/(g.h);磷的吸收速率在31℃,总磷为6．3μmol/L时最大,达0.17μmol/(g.h),温度与营养盐浓度有显著的交互作用效应。（2）当氮浓度一定时,环境氮磷比对氮的吸收率无显著影响,但对磷的吸收速率有显著影响,藻中收的氮磷比随环境氮磷比的不同而变化,（3）对3种不同化合态氮的吸收速率与培养液中各种氮占总无机氮的比例呈正相关,当三比例相同时,对NH4^ -N、NO3^--N格NO2^-析吸收分别占总吸收氮的40．7％、28．5％和30．8％。     

塔玛亚历山大藻对氮和磷的吸收及其生长特性

参照塔玛亚历山大藻(Alexandrium tamarense)赤潮爆发时的物理条件,以f／2加富的人工海水为培养基,设定了不同的氮、磷水平,研究了在室内批量培养条件下,塔玛亚历山大藻对无机氮、磷的吸收和无机氮、磷对塔玛亚历山大藻细胞生长的影响．结果表明,3种氮浓度条件下,塔玛亚历山大藻的比生长速率几乎没有差异,但低氮(0．0882mmol·L-1)条件下,藻细胞的生物量最低;中氮(0．882mmol·L-1)条件下,藻细胞具有最大的生物量,分别比高氮(2．646mmol·L-1)和低氮下增加44．7％和53．6％．随着培养基中磷浓度的升高,藻细胞生物量也升高,在高磷(0．108mmol·L-1)条件下达到最大值17200cell·ml-1,但在中磷(0．036mmol.L-1)条件下藻细胞具有最大的比生长速率．藻细胞对氮、磷的吸收速率与生长状态有密切关系,氮、磷限制条件下生长的藻细胞对氮、磷有快速的吸收．研究显示,低的N／P比有利于塔玛亚历山大藻的生长分裂,对数生长后期适当补氮则有利于其生物量的积累．     

不同磷浓度对丛枝菌根真菌吸收同化外源氮能力的影响

以高粱（ Sorghum bicolor）为宿主植物,丛枝菌根（ arbuscular mycrohiza,AM）真菌根内球囊霉（ Glomous intraradices）为接种菌剂,三室隔离培养盒为培养容器,通过在菌丝室添加不同浓度梯度磷素及外源氮NH4 NO3、Gln,研究磷浓度对AM真菌同化吸收不同外源氮能力的影响。实验结果显示：AM真菌能够侵染于高粱植物根系,但菌根侵染率差异不显著;在高磷浓度下孢子数量显著高于低磷浓度下孢子数量;菌丝室内根外菌丝（ ERM）干重在低磷浓度下含量最高,且以Gln为外源氮时含量比不加氮源和NH4 NO3为氮源时高;低磷浓度促使高粱地上茎叶和地下菌根干重显著提高,叶绿素含量在不同处理下没有显著差异。茎叶总氮含量均在以NH4 NO3为外源氮时最高,不同磷浓度下其总氮含量为P30＆gt;P120＆gt;P0＆gt;P60,菌根精氨酸含量在Gln为外源氮时含量比其他氮源下高,且在低磷（P30）浓度下含量最高。研究表明AM真菌对于吸收同化外源氮的能力与其生长环境中磷浓度高低有关,在低磷浓度下更利于AM真菌根外菌丝同化吸收外源氮,且对NH4＋形式氮源吸收能力最强。     

镉对固定化小球藻除磷效果的影响

采用人工配制污水进行静态模拟实验,研究了镉对被海藻酸钙凝胶包埋固定的小球藻去除磷能力的影响.结果表明:在各光照及pH条件下,镉对固定化小球藻吸收磷的效果随着实验时间的推移而变化,在实验的第一天时影响最大;总体而言,镉抑制了固定化小球藻的除磷能力,但在某些条件下镉反而提高了藻对磷的吸收;固定化处理减弱了镉对小球藻除磷能力的影响.具体的光照、pH值与镉的影响效果的关系尚待进一步探讨.     

培养基磷缺乏对黄瓜毛状根生长、抗氧化酶活性及氮源利用的影响

采用液体培养的方法研究了培养基磷缺乏对黄瓜毛状根生长及其抗氧化酶活性及培养基中氮源和钙利用的影响.结果表明,黄瓜毛状根在完全缺磷的培养基中几乎不能生长;而培养基无机磷缺乏会抑制黄瓜毛状根的生长,且浓度越低,其抑制作用越明显,毛状根变得越纤细而长,侧根数减少且短小.与全磷培养相比,磷缺乏培养基培养的黄瓜毛状根可溶性蛋白含量明显偏低,但其SOD和POD活性则明显升高.与完全缺磷(对照)相比,在培养过程中不同无机磷浓度培养的黄瓜毛状根的SOD和POD活性均比对照低.当黄瓜毛状根在不同磷缺乏浓度的液体培养基中培养时,随着培养时间的延长,培养基的电导率逐步下降,并与培养基起始无机磷浓度成正比;其培养基的铵态氮和硝态氮不断被吸收和利用,培养至15d时,培养基中的铵态氮已绝大部分被消耗完毕,但直至培养30d时培养基的硝态氮仍未被消耗完毕.培养基中无机磷缺乏会降低黄瓜毛状根对培养基硝态氮的吸收和消耗以及抑制黄瓜毛状根对钙的吸收.而适当提高培养基的无机磷浓度可促进黄瓜毛状根对培养基中钙的吸收和消耗.     

重要环境因子对小球藻去除污水中氮磷的影响

对小球藻去除污水中氮磷的性能进行了研究,考察了初始氮磷浓度、氮磷比、光照条件和pH等因素对其去除效率的影响。结果表明,在初始氮磷浓度分别在35 mg/L和7 mg/L以下时去除率接近100%;氮磷比为5∶1和10∶1,小球藻第4 d基本完全去除了污水中的氨态氮,而氮磷比对小球藻的除磷能力没有显著影响;在初始氨态氮或总磷浓度相同的条件下,光照条件(L/D为24 h∶0 h和12 h∶12 h)对氮磷去除效果的无明显差异性（P＞0.05）,而随着氮磷浓度的增加,连续光照条件逐渐展现出去除氮磷的优势;小球藻在pH 7～8范围内对氨态氮的去除率最佳,pH 5～7范围内,对总磷的去除率最佳。     

柳树新无性系(A42)对富营养水体不同浓度磷的吸收和净化机制

磷是评价水体富营养化的因子之一,也是植物生长必需营养元素,研究速生木本植物对富营养水体中磷的吸收具有重要意义.本研究以旱柳新无性系A42为对象,于2017年7—9月在温室大棚中进行浮床水培试验,研究了旱柳对不同磷营养水平水体(低磷0.1、0.2 mg·L^-1;中磷1.0、2.0 mg·L^-1;高磷10.0 mg·L^-1)的吸收和净化机制.结果表明:旱柳能有效净化水体中的磷营养(21 d达到79%以上),去除量与水体磷浓度呈正相关,但去除率随水体磷浓度增加呈先升高后降低趋势.旱柳可于7 d内将磷浓度为0.1～1 mg·L^-1的富营养水体中磷浓度降低至富营养阈值(0.016～0.032 mg·L^-1).旱柳富集同化的磷含量占水体磷总输入量的29.0%～66.9%,富集同化量与富集同化率分别与水体磷浓度呈正相关和负相关.旱柳在不同磷浓度水体中均能正常生长,根冠比随水体磷浓度下降而显著增加.氮、磷在旱柳体内积累均表现为茎>叶>根,旱柳的氮、磷转运系数均大于3,在高磷浓度水体中,氮磷营养在旱柳的茎部大量积累,氮、磷转运系数分别显著增加至4.53±0.24和4.92±0.62.表明旱柳在不同磷浓度富营养水体中均能正常生长且有良好的净化能力,能够通过富集转运磷营养至地上部来减少二次污染.实际应用中,对于低磷浓度水体,适合做短期净化;对于高磷浓度水体,适合做长期净化.     

Effect of external electric current on adsorption of lead by Penicillium polonicum

Abstract

Lead is a major source of environmental pollution that has recently been the focus of a great deal of research. Bioremediation has been shown to be effective in remediation of lead pollution. Penicillium polonicum is a fungus with highly efficient adsorption of lead. In this study, the influence of electric current on the growth characteristics and adsorption of lead by the strain were investigated through applying different external voltages (1.5, 1.25, 1.0, 0.75, and 0.5?V). The results indicated that the electric current with voltage ranges from 1.0 to 1.25?V could promote the adsorption of lead. In addition, morphological characteristics and the quantity of lead-containing minerals formed on the surface of P. polonicum differed greatly under different experimental conditions. Further, the electric current intensity and electric energy consumption at voltages of 1.0, 1.25, and 1.5?V were higher than the blank control group, suggesting that the strain could utilize the energy supplied by an external electrochemical workstation to improve lead adsorption. After applying an external current, the lead adsorption of P. polonicum was affected by electric current changing the growth environment of the fungus and the electron transfer reaction between electrodes and P. polonicum.     

DNA methylation impacts the cleavage activity of Chlorella virus topoisomerase II

Topoisomerase II from Paramecium bursaria chlorella virus-1 (PBCV-1) and chlorella virus Marburg-1 (CVM-1) displays an extraordinarily high in vitro DNA cleavage activity that is 30-50 times higher than that of human topoisomerase IIalpha. This remarkable scission activity may reflect a unique role played by the type II enzyme during the viral life cycle that extends beyond the normal control of DNA topology. Alternatively, but not mutually exclusively, it may reflect an adaptation to some aspect of the viral environment that differs from the in vitro conditions. To this point, the genomes of many chlorella viruses contain high levels of N6-methyladenine (6mA) and 5-methylcytosine (5mC), but the DNA employed in vitro is unmodified. Therefore, to determine whether methylation impacts the ability of chlorella virus topoisomerase II to cleave DNA, the effects of 6mA and 5mC on the PBCV-1 and CVM-1 enzymes were examined. Results indicate that 6mA strongly inhibits DNA scission mediated by both enzymes, while 5mC has relatively little effect. At levels of 6mA and 5mC methylation comparable to those found in the CVM-1 genome (10% 6mA and 42% 5mC), the level of DNA cleavage decreased approximately 4-fold. As determined using a novel rapid quench pre-equilibrium DNA cleavage system in conjunction with oligonucleotide binding and ligation assays, this decrease appears to be caused primarily by a slower forward rate of DNA scission. These findings suggest that the high DNA cleavage activity of chlorella virus topoisomerase II on unmodified nucleic acid substrates may reflect, at least in part, an adaptation to act on methylated genomic DNA.     

固定化小球藻产氧及光合速率的研究

通过对固定化小球藻产氧及光合速率的研究,进一步解决水产养殖水体溶解氧不足的问题,为生物增氧技术投入使用奠定基础。固定化具有较高的生物量及生物活性,在研究中被广泛使用。运用固定化技术对固定化小球藻产氧及光合速率进行了研究,结果表明,固定化小球藻具有较好的生物量及生物活性,海藻酸钠+羧甲基纤维素钠+硅藻土作为固定化基质有利于小球藻的放氧,其最高放氧量介于第3-4天,对于1 L水体增氧的最适固定化小球藻体积为150 mL,固定化小球藻的光合速率明显高于游离态小球藻。固定化技术增加了小球藻生物量和生物活性,具有较好的生物增氧特性,是较好的生物增氧材料。     

Attenuating effect of chlorella supplementation on oxidative stress and NFkappaB activation in peritoneal macrophages and liver of C57BL/6 mice fed on an atherogenic diet

This study was designed to investigate whether chlorella supplementation may ameliorate oxidative stress and nuclear factor kappa B (NFkappaB) activation in peritoneal macrophages and liver of C57BL/6 mice fed on an atherogenic diet. The animals were maintained on an atherogenic diet (control), or an atherogenic diet supplemented with 3% (w/w) chlorella or 5% (w/w) chlorella for 12 wks. The plasma and hepatic lipid levels were not affected by chlorella supplementation. Hepatic thiobarbituric acid-reactive substances and superoxide anion production in peritoneal macrophages were significantly lower in the 5% chlorella group (p<0.05), but the glutathione level was not altered by chlorella supplementation. The hepatic antioxidative enzyme activities of Cu, Zn-superoxide dismutase and catalase were higher in the mice fed on the 5% chlorella diet (p<0.05). The plasma aspartate aminotransferase activity was lower in the mice fed on the chlorella-containing diets (p<0.05), whereas the alanine aminotransferase activity was not affected by chlorella supplementation. The NFkappaB nuclear binding activities of peritoneal macrophages and liver were significantly lower in the 5% chlorella groups (p<0.05). These results suggest that chlorella supplementation may attenuate oxidative stress by reducing reactive oxygen production and increasing antioxidative processes, thus suppressing inflammatory mediator activation in peritoneal macrophages and liver.     

A single amino acid change restores DNA cytosine methyltransferase activity in a cloned chlorella virus pseudogene.

The chlorella virus PBCV-1 contains an open reading frame, named P17-ORF4, which differs by eight amino acids from a DNA cytosine methyltransferase, M.CviJI, encoded by a different chlorella virus IL-3A. Whereas IL-3A expresses M.CviJI, which methylates the central cytosine in (A/G)GC(T/C/G) sequences, P17-ORF4 is non-functional. Gene fusions between P17-ORF4 and M.CviJI and site-directed point mutations revealed that changing Gln188 to Lys188 abolishes M.CviJI methyltransferase activity. Conversely, changing Lys188 in P17-ORF4 to Gln188 results in M.CviJI activity. The other altered seven amino acids do not appear to affect M.CviJI activity.     

Adsorption of nitrogen and phosphorus by intact cells and cell wall polysaccharides of Microcystis

Microcystis blooms can move vertically and horizontally in natural water bodies, which often causes a rapid change of nutritional environment around Microcystis cells. To evaluate the capability of Microcystis capturing nitrogen (N) and phosphorus (P) when environmental nutrient levels change, we studied N and P adsorption of two different forms of Microcystis aeruginosa strains, a colonial strain XW01 and a unicellular strain PCC 7806, and a green alga Chlorella pyrenoidosa to different concentrations of nitrate, ammonium and phosphate in 30 min. The results showed that XW01 had much stronger adsorption capacity than PCC7806 and Chlorella. As main components of the cell wall, the polysaccharides of XW01 displayed different adsorption capacities in different N and P concentrations, their adsorption capabilities rose higher with the N or P concentration increase. Comparing with pH 7.0, XW01 could adsorb much more ammonia and phosphate in alkaline condition (pH 9.0), although the nitrate adsorption decreased a little.     

The effect of processing of Chlorellavulgaris: K-5 on in vitro and in vivo digestibility in rats

Two experiments were done to clarify whether or not cell rupture is necessary to improve the digestibility of major components of Chlorella vulgaris: K-5. Chlorella was treated with or without high pressure homogenization (1 × 10⁸ N/m² at less than −20°C) after a heating process (100-120°C). Chlorella (air-dry matter) contained 934 g dry matter and 244 g essential amino acids (total)/kg. Chemical composition was hardly altered irrespective of the treatment. In the first experiment, pepsin digestibility of chlorella protein was determined in vitro. The cell rupture by high pressure homogenization caused a small but significant improvement in pepsin digestibility of chlorella protein compared with the control. In the second experiment, total tract apparent digestibilities of chlorella were determined in the rat. Digestibility of chlorella protein was significantly enhanced by high pressure homogenization, but the difference (88.6% vs. 87.4%, P < 0.01) due to treatment was small and similar to that observed in the in vitro experiment. These results suggested that Chlorella strain vulgaris: K-5 may be an efficient protein source even without cell rupture.     

Adsorption and decomposition mechanism of hexogen (RDX) on Al(111) surface by periodic DFT calculations

The adsorption of hexogen (RDX) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and aluminum atoms induce the N?O and N?N bond breaking of the RDX. Subsequently, the dissociated oxygen atoms, NO₂ group and radical fragment of RDX oxidize the Al surface. The largest adsorption energy is ?835.7 kJ mol^–1. We also investigated the adsorption and decomposition mechanism of RDX molecule on the Al(111) surface. The activation energy for the dissociation steps of V4 configuration is as large as 353.1 kJ mol^–1, while activation energies of other configurations are much smaller, in the range of 70.5–202.9 kJ mol^–1. The N?O is even easier than the N?NO₂ bond to decompose on the Al(111) surface.     

不同来源小球藻对岩溶水Ca2+、HCO3-利用的初步研究

以外源小球藻和岩溶区筛选出的土著小球藻为研究对象, 在封闭体系中比较研究了两种不同来源小球藻对典型岩溶水中Ca2+、HCO3-的利用、藻细胞数量与其对Ca2+、HCO3-的利用率的关系和体系pH的变化。结果表明, 土著小球藻利用Ca2+、HCO3-的能力强于外源小球藻, 但外源小球藻对Ca2+的利用量高于土著小球藻, 而二者对HCO3-的利用量相同, 并且外源小球藻能够以胞外CaCO3形式产生沉淀, 而土著藻则不能形成沉淀。其次两体系中pH的变化显示, 两种小球藻光合作用都是先以水体中CO2为光合作用碳源, 然后利用HCO3-。外源小球藻能将岩溶水中29.648%的HCO3-吸收, 而土著藻能将40.625%的HCO3-通过其在食物链中的初级生产地位将岩溶碳汇转化进入到生态系统, 表现为净碳汇效应。