Cadmium removal by living cells of the marine microalga Tetraselmis suecica

Cadmium removal by living cells of the marine microalga Tetraselmis suecica was tested in cultures exposed to different cadmium concentrations (0.6, 3, 6, 15, 30 and 45 mg/l). The EC50 for growth was 7.9 mg Cd/l after six days of exposure. The cadmium removed was proportional to the concentration of this metal in the medium and it was dependent on the time of exposure; cultures with higher cadmium concentration removed a higher amount of this metal. In cultures exposed to 0.6 mg/l, T suecica cells removed 98.1% of added cadmium with 0.392 x 10(-6) microg Cd/cell, whereas in cultures with 45 mg/l only 7.7% was removed with 16.052 x 10(-6) microg Cd/cell. The highest amount of cadmium removed per liter of culture was observed in cultures exposed to 6 mg/l, with 3.577 mg/l of cadmium. After six days of incubation, the higher proportion of cadmium was bioaccumulated intracellularly in all cultures except in 45 mg/l cultures, the percentage of intracellular cadmium being always more than 50%. The highest percentage of bioadsorbed cadmium (60.1%) was found in cells of cultures with the highest cadmium concentration (45 mg/l). Furthermore, a relation between intracellular cadmium and the concentration of sulfhydryl groups was observed.     

Cadmium biosorption by Sphingomonas paucimobilis biomass

Among microorganisms isolated in Bangkok, the gram-negative bacterium Sphingomonas paucimobilis exhibited the greatest cadmium tolerance. It was able to survive in the medium containing cadmium as high as 200 mg/l. However, concentrations of cadmium at 25-200 mg/l inhibited its growth. The biosorption properties for cadmium of this bacterial biomass and the effects of environmental factors (i.e., biosorbent type, initial pH and biosorbent concentration) on the cadmium biosorption were explored. The results showed that the cadmium removal capacity of living cells was markedly higher than that of nonliving cells. Cadmium biosorption by S. paucimobilis biomass was also affected by the initial pH and biosorbent concentration.     

Cadmium biosorption by <Emphasis Type="Italic">Bacillus</Emphasis><Emphasis Type="Italic"> circulans</Emphasis> strain EB1

Summary A heavy metal resistant bacterium, Bacillus circulans strain EB1 showed a high cadmium biosorption capacity coupled with a high tolerance to this metal when grown in its presence. Bacillus circulans EB1 cells grown in the presence of 28.1 mg cadmium/l were capable of removing cadmium with a specific biosorption capacity of 5.8 mg Cd/g dry wt biomass in the first 8 h. When the cells were pre-conditioned with low concentrations of cadmium in pre-grown medium, the uptake was increased to 6.7 mg Cd/g dry wt biomass. The maximum uptake of␣cadmium was during mid-logarithmic phase of growth. The resting cells (both wet and dry) of EB1 were also able to biosorb cadmium. Specific biosorption capacities of wet and dry biomass were 9.8 and 26.5 mg Cd/g dry wt biomass, respectively. Maximum cadmium removals by both wet and dry cells were at pH 7.0. The results showed that the cadmium removal capacity of resting cells was markedly higher than that of growing cells. Since both growing and resting cells had a high biosorption capacity for cadmium, EB1 cells could serve as an excellent biosorbent for removal of cadmium from natural environments.     

The mechanism of cadmium removal from aqueous solution by nonmetabolizing free and immobilized live biomass of Rhizopus oligosporus

A preliminary study on the removal of cadmium by nonmetabolizing live biomass of Rhizopus oligosporus from aqueous solution is presented. The equilibrium of the process was in all cases well described by the Langmuir sorption isotherm, suggesting that the process was a chemical, equilibrated and saturable mechanism which reflected the predominantly site-specific mechanism on the cell surface. A curve of Scatchard transformation plots reflected the covalent nature of Cd²⁺ adsorption by the cells. The maximum cadmium uptake capacities were 34.25 mg/g for immobilized cells and 17.09 mg/g for free cells. Some factorial experiments in shake flasks were performed in order to investigate the effect of different initial cadmium concentrations and biomass concentrations on the equilibrium. Experimental results showed a reverse trend of the influence of the immobilized and free biomass concentration on the cadmium specific uptake capacity. The immobilized cells had a higher specific cadmium uptake capacity with increasing biomass concentrations compared to free cells. In a bioreactor, the cadmium uptake capacity of immobilized cells (q_max = 30.1–37.5 mg/g) was similar to that observed in shake flask experiments (q_max = 34.25 mg/g) whereas with free cells the bioreactor q_max of 4.8–13.0 mg/g; was much lower than in shake flasks (q_max = 17.09 mg/g), suggesting that cadmium biosorption by immobilized cells of R. oligosporus might be further improved in bigger reactors. EDAX and transmission electron microscopic experiments on the fungal biomass indicated that the presence of Cd²⁺ sequestrated to the cell wall was due to bioadsorption.     

Phenols and phenol oxidases are involved in cadmium accumulation in the water plants Nymphoides peltata (Menyanthaceae) and Nymphaeae (Nymphaeaceae)

This comparative study investigates the mechanism of cadmium accumulation in the semiaquatic plant Nymphoides peltata (Menyanthaceae) and the aquatic plant Nymphaea (Nymphaeaceae). It was conducted as part of an ongoing study of the use of water plants for phytoremediation. Epidermal structures, known as hydropotes, are located on the abaxial epidermis of the leaf laminae of Nymphoides peltata and are shown to contain phenols, peroxidase and polyphenol oxidase activities. When plants are subjected to 50 mg/l of cadmium in the growth medium, these hydropotes accumulate cadmium. Cadmium-induced increases in phenols, peroxidase and polyphenol oxidase activities were determined in plant extracts. Cadmium binding by polymerized phenols was demonstrated in vivo. In comparison with Nymphaeae epidermal glands, N. peltata hydropotes are larger, open, and create bigger crystal, the latter principally composed of calcium and, proportionally, less cadmium. Although both plants showed similar levels of cadmium accumulation, N. peltata was sensitive while Nymphaeae was resistant to this cadmium level. It is suggested that in these water plants the main mechanism for cadmium accumulation is based on the trapping of cadmium crystals by polymerized phenols in specialized epidermal structures and this is due to peroxidase and polyphenol oxidase activities. Nymphaeae, with greater peroxidase activity and more polyphenols, is more resistant to this heavy metal than N. peltata.     

镉胁迫小海绵羊肚菌氧化损伤及其抗氧化防御

羊肚菌Morchella是全球广泛分布的食药用真菌,重金属镉(Cd)在羊肚菌中的积累受到越来越多的关注。然而,羊肚菌镉积累的机理尚不清楚。本研究通过在0–5.0mg/LCd浓度环境中培养小海绵羊肚菌Morchella spongiola,测定Cd胁迫下其菌丝生长速率、丙二醛(MDA)、过氧化氢(H₂O₂)、超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)、谷胱甘肽(GSH)、抗坏血酸(ASA)及细胞Cd积累量等生理生化指标,旨在明晰小海绵羊肚菌响应Cd毒害的抗氧化防御响应机理。结果表明随着Cd浓度的增加,小海绵羊肚菌菌丝生长呈现出“升-降-升-降”的双峰响应变化,其中0.15、0.90和1.50 mg/L为菌丝生长Cd浓度关键拐点。Cd胁迫导致的氧化损伤与其初始浓度呈现正相关,胁迫3 d时MDA和H₂O₂含量显示出较大提升,5.0 mg/L处理组MDA和H₂O₂含量比对照组分别高出5.80倍和6.08...     

The effects of heavy metals on common carp white blood cells in vitro

The in vitro effects of cadmium, copper, lead and zinc, and various cadmium compounds (chloride, sulphate and nitrate) on common carp (Cyprinus carpio) lymphocyte viability and phagocyte activity, were evaluated. The percentage of dead lymphocytes was determined after Trypan blue staining, and phagocyte activity was measured by using the nitroblue tetrazolium (NBT) reduction test. Lead was the most toxic to lymphocytes--the maximum mortality exceeded 30%, and was significantly higher at 1 microM of lead, compared to the control. The maximum mortality caused by cadmium was below 10%, but was significantly elevated with 5 microM or more of cadmium. Zinc induced lymphocyte mortality from 10 microM, whilst no effect was observed with copper. The incubation of full blood with the three cadmium compounds (at 5mg/l of cadmium) showed that cadmium nitrate and cadmium sulphate were more toxic (over 35% and 25% mortality, respectively) than cadmium chloride (about 15% mortality). This was confirmed by the results of tests on isolated cells--1mg/l of cadmium as nitrate and sulphate increased lymphocyte mortality compared to the control and cadmium chloride. Phagocytic activity was less sensitive to heavy metals than was lymphocyte viability. It was significantly reduced following exposure to 50 microM and 100 microM cadmium, and 100 microM zinc, but no effects were observed with either lead or copper.     

Removal of hexavalent chromium by fungal biomass of <Emphasis Type="Italic">Mucor racemosus</Emphasis>: influencing factors and removal mechanism

This study reported the hexavalent chromium removal by untreated Mucor racemosus biomass and the possible mechanism of Cr (VI) removal to the biomass. The optimum pH, biomass dose, initial Cr (VI) concentration and contact time were investigated thoroughly to optimize the removal condition. The metal removal by the biomass was strongly affected by pH and the optimum pH ranged from 0.5 to 1.0. The residual total Cr was determined. It was found that dichromate reduction occurred at a low very low pH value. At biomass dose 6 g/l, almost all the Cr (VI) ions were removed in the optimum condition. Higher removal percentage was observed at lower initial concentrations of Cr (VI) ions, while the removal capacity of the biomass linearly depended on the initial Cr (VI) concentration. More than half of Cr (VI) ions were diminished within 1 h of contact and removal process reached a relative equilibrium in approximately 8 h. Almost all of the Cr (VI) ions were removed in 24 h when initial concentrations were below 100 mg/l. The equilibrium data were fitted in to the Langmuir and the Freundlich isotherm models and the correlated coefficients were gained from the models. A Fourier transform infrared spectra was employed to elucidate clearly the possible biosorption mechanism as well.     

镉对小鼠精子和生精细胞超微结构及生精细胞bcl-2、bax基因表达的影响

研究镉暴露对小鼠附睾精子和睾丸生精细胞超微结构的变化以及镉对生精细胞凋亡相关基因bcl-2、bax表达水平的影响。采用24只雄性ICR小鼠随机分为4组,每组6只,分别以0.183、0.915、1.83mg/kg氯化镉腹腔注射,每天1次,连续5次,设阴性对照生理盐水组。于第6天透射电镜观察附睾精子超微结构、睾丸生精细胞核和线粒体超微结构的变化,免疫组化方法检测生精细胞Bcl-2、Bax表达水平。透射电镜观察显示,0.183mg/kg组精子超微结构无显著性变化,0.915mg/kg组精子头部两侧膜与头部胞质间隙轻微扩大,线粒体嵴间腔扩大且轻度空泡化,但与对照组相比无统计学意义(P>0.05)。1.83mg/kg组头部两侧膜与胞质间隙扩大,与对照组相比有显著性差异(P<0.05),尾部线粒体嵴间腔扩大且轻度空泡化,与对照组相比有显著性差异(P<0.05)。3种剂量处理组睾丸生精细胞核超微结构异常发生率显著高于对照组(P<0.05),且随着处理浓度的升高异常发生率升高;1.83mg/kg组线粒体肿胀空泡化发生率显著高于对照组(P<0.05)。3种剂量实验组生精细胞Bcl-2表达水平(吸光度)显著低于对照组(P<0.01),0.915mg/kg组Bax表达水平显著高于对照组和0.183、1.83mg/kg组(P<0.01)。3种剂量实验组Bcl-2/Bax吸光度比值显著低于对照组(P<0.01);0.915mg/kg组Bcl-2/Bax比值显著低于1.83mg/kg组(P<0.01)。上述结果提示:高浓度镉诱导附睾精子超微结构改变,高中低浓度镉致睾丸生精细胞超微结构的改变,生精细胞超微结构发生凋亡现象。镉对Bcl-2、Bax表达水平的改变可能是生精细胞凋亡的分子机制之一。     

The recovery of heavy metals using encapsulated microbial cells

We prepared capsules containingSaccharomyces cerevisiae andZoogloea ramigera cells for the removal of lead (II) and cadmium ions. Microbial cells were encapsulated and cultured in the growth medium. TheS. cerevisiae cells grown in the capsule did not leak through the capsule membrane. The dried cell density reached to 250 g/l on the basis of the inner volume of the 2.0 mm diameter capsule after 36 hour cultivation. The dry whole cell exopolymer density of encapsulatedZ. ramigera reached to 200 g/L. The capsule was crosslinked with triethylene tetramine and glutaric dialdehyde solutions. The cadmium uptake of encapsulated whole cell exopolymer ofZ. ramigera was 55 mg Cd/g biosorbent. The adsorption line followed well Langmuir isotherm. The lead uptake of the encapsulatedS. cerevisiae was about 30 mg Pb/g biomass. The optimum pH of the lead uptake using encapsulatedS. cerevisiae was found to be 6. Freundlich model showed a little better fit to the adsorption data than Langmuir model. 95 percent of the lead adsorbed on the encapsulated biosorbents was desorbed by the 1 M HCl solution. The capsule was reused 50 batches without loosing the metal uptake capacity. And the mechanical strength of the crosslinked capsule was retained after 50 trials.     

Salt-induced osmotic stress for glutathione overproduction in Candida utilis

The effect of NaCl-induced osmotic stress on glutathione (GSH) production was investigated in Candida utilis. Based on the fact that NaCl stress can enhance GSH production but inhibit cells growth simultaneously, the novel strategies of multiple osmotic stresses with different NaCl additions (0.2 mol/l at 4 h, 0.4 mol/l at 8 h, and 0.6 mol/l at 12 and 16 h) were developed for GSH overproduction. After 30 h cultivation, GSH yield reached 238 mg/l and intracellular GSH content was 2.34%, increased by 66.4% and 70.7% respectively compared to the control. Further applying the strategies to 7 l fermentor, GSH yield of 356 mg/l was achieved at 30 h, which was 65.6% higher than the control. Moreover, NaCl stress led to an increase in intracellular cysteine content and activities of γ-glutamylcysteine synthetase, GSH synthetase and GSH reductase, explaining the mechanism involved in inducing cellular GSH accumulation.     

Chromium and cadmium removal from wastewater using duckweed - Lemna gibba L. and ultrastructural deformation due to metal toxicity

Phytoremediation potential of Lemna gibba was evaluated for chromium (Cr) and cadmium (Cd) under laboratory conditions for variable metal load of 1?mg/l, 3?mg/l, 5mgl, 7?mg/l and 9?mg/l, respectively, for 7 and 15?days of treatment period. Effects of both metals on structural attributes of L. gibba were also analyzed by Scanning Electron Microscopic (SEM) study. The metal removal percentage by L. gibba for Cr metal was found in the range of 37.3% to 98.6% and for cadmium it was found within the range of 81.6% to 94.6%. Bio concentration factor (BCF) of L .gibba was observed within the range of 37 to 295 for Cr metal and for Cd metal it ranged from 237 to 1144, which shows that the plant is a hyper accumulator for Cd metal and moderate accumulator for Cr metal. Statistical analysis (Two-way ANOVA) was performed on experimental results to confirm the individual effect of metal concentration and treatment period as well as cumulative effect of both factors together on percentage metal removal and on BCF. Research studies indicated that with the progress of treatment period metal removal percentage increases but increasing metal load during experiment negatively co-relates the metal removal percentage and BCF.     

Color removal ability of <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis> in relation to lignin peroxidase and manganese peroxidase produced in molasses wastewater

Decolorization of molasses wastewater (MWW) from an ethanolic fermentation plant by Phanerochaete chrysosporium was studied. By diluting MWW properly (10%v/v) and incubating it with an appropriate concentration of the spores (2.5 × 10⁶/ml), extensive decolorization occurred (75%) on day 5 of the incubation. The colour removal ability was found to be correlated to the activity of ligninolytic enzyme system: lignin peroxidase (LiP) activity was 185 U/l while manganese peroxidase (MnP) activity equaled 25 U/l. Effects of some selected operating variables were studied: manganese(II), veratryl alcohol (VA), glucose as a carbon source and urea and ammonium nitrate, each as a source of nitrogen. Results showed that the colour reduction and LiP activity were highest (76% and 186 U/l, respectively) either when no Mn(II) was added or added at the lowest level tested (0.16 mg/l to provide 0.3 mg/l). Activity of MnP was highest (25 U/l) when Mn(II) added to the diluted MWW at the highest level (100 ppm) while activity of LiP was lowest (7.1 U/l) at this level of added Mn(II). The colour reduction in the presence of the added VA was shown to be little less than in its absence (70 vs. 75%). When urea as an organic source of nitrogen for the fungus, was added to the MWW, the decolorizing activity of P. chrysosporium decreased significantly (15 vs. 75%) and no activities were detected for LiP and MnP. Use of ammonium nitrate as an inorganic source of nitrogen did not show such a decelerating effects, although no improvements in the metabolic behavior of the fungus (i.e., LiP and MnP activities) deaccelerating was observed. Effects of addition of glucose was also discussed.     

Responses of <Emphasis Type="Italic">Rhodotorula</Emphasis> sp. Y11 to cadmium

Some aspects of the cellular responses to cadmium were extensively investigated in the yeast Rhodotorula sp. Y11. Scanning electron microscopy indicated that accumulation of cadmium in the Y11 did not cause any visible effects on cell morphology. More than 20% yeast cells still showed viability after 15 h of cadmium accumulation under 100 mg l⁻¹ cadmium concentration, and transmission electron microscopy analysis showed that plasmolysis and thickened cell wall were not observed in all of the cells. In the presence of cadmium, the activities of superoxide dismutase (SOD) and catalase (CAT) were all greater than the control, but the increase was in a dose-independent manner. Changes in SOD and CAT activities were also dependent on the time of exposure. Therefore, it suggests that antioxidative defenses play an important role in cadmium tolerance in Rhodotorula sp. Y11. Nondenaturing polyacrylamide gels revealed only one SOD isoforms in Y11 even under exposure to cadmium.     

秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。     

Cadmium uptake by non-viable biomass from a marine brown algaEcklonia radiata turn

Biomass of non-viable and dried brown marine algaeEcklonia radiata Turn. was used to examine its cadmium uptake capability. Twelve different pretreatments on the algal biomass were prepared. Among these pretreatments, the algal biomass, which treated with 0.1 M NaOH and kept in water bath (100°C, 18 h) followed by washing with distilled water and squeezing, showed the highest amount of cadmium uptake as 1634±195 mg/g dry biomass at pH 4.0 and 50°C. Adsorption temperatures and pH levels played some important role in cadmium uptake. However, cadmium uptake decreased dramatically at a lower pH than 4.0. Freundlich adsorption isotherm showed potent cadmium uptake capacity of the non-viable biomass. Pretreatments on the nonviable algal biomass shown in this study may enhance the cadmium removal in the industrial wastewater.     

Incorporation of cadmium into proteins in a cadmium tolerant fungi

Aspergillus carbonarius and a strain of Penicillium, a cadmium tolerant fungi, are able to metabolize cadmium chloride up to 2% (w/v). Their amino acids analysis on cadmium free and cadmium chloride containing media indicated certain disorders in their metabolic activities. Cystathionine was only detected in both fungi in the presence of cadmium chloride. However, cadmium was incorporated into several types of low and high molecular weight proteins. The amino acids hydrolyzates of a cadmium containing protein are characterized by the presence of high levels of sulfur amino acids; cysteine and methionine. Ethylasparagine was detected in the hydrolyzate of that cadmium containing protein as well.     

Cadmium removal from water environment by a fungus Volveriella volvacea

Biosorption technique was used for removal of cadmium under different conditions from water environment using a biosorbent, Volveriella volvaceas, locally growing fruit bodies of mushroom. Effects of different parameters like pH, sorbent concentration, ionic strength on the removal efficiency of cadmium by V. volvacea were carried out in continuation with adsorption kinetics and equilibrium isotherm experiments. From the kinetics studies it was found that nearly 95% of the total cadmium removal was achieved from cadmium spiked distilled water within first 15 minutes. Isotherm data was best fitted to linearised Langmuir equation and the sorption capacity was found to be varying from 9.13 to 9.33 mg/g for different sizes of sorbent. The uptake of cadmium(II) is a function of pH of the solution and increases with the increasing pH. Increasing ionic strength and the presence of soluble complexing agents such as ethylene diamine tetraacetic acid (EDTA) decrease the sorption of cadmium (II). The presence of other diavalent cations like calcium and magnesium impedes the uptake of cadmium (II). The presence of chloride ion has no significant effect on cadmium (II) removal. The spent biosorbent can effectively be regenerated with acid and can then be reused.The present work was carried out by the financial support in terms of fellowship under the cultural exchange programme of the Indo-Bangladesh government. Special thanks to the Director, Bangladesh Institute of Technology, Dhaka, Bangladesh, for providing leave, which enabled the author in carrying out the research work.     

Studies on the accumulation of cadmium by a strain of Proteus mirabilis

Abstract A bacterium isolated from a wastewater plant sludge, identified as Proteus mirabilis , was tested for cadmium tolerance and accumulation capacity. The organism was able to grow in the presence of Cd²⁺ up to 300 mg l⁻¹.
Accumulation of cadmium is reported for growing and non-growing cells of the organism. In non-growing cultures a 70% removal of cadmium was observed when the initial concentration of Cd²⁺ was 1 mg l⁻¹ whereas at the same concentration the removal by growing cells was only 22%. The metal was shown to be associated with the cell envelope (80%) and accumulated in the cytoplasm (20%).