Metals biosorption by sodium alginate immobilizedChlorella homosphaera cells

Summary Cadmium and zinc biosorption, alone or in combination, was investigated with sodium alginate immobilizedChlorella homosphaera cells. Concentrations ranging from 20.0 to 41.0mg/l cadmium, 75.0 and 720.0mg/l zinc were tested and, in all cases, the metal removal achieved values near 100%. When these metals were put in combination a decrease in the rate of absorption was detected. Gold was also tested in the immobilized system and 90% of the initial metal added was recovered in a solution containing 213.0mg/l of the metal, the alginic matrix being responsible for 40% gold uptake.     

Mechanism of Biosorption of Heavy Metals by Mucor rouxii

Fungi such as Aspergillus niger and Mucor rouxii are capable of removing heavy metals from aqueous solutions. The role various functional groups play in the cell wall of M. rouxii in metal biosorption of lead, cadmium, nickel and zinc was investigated in this paper. The biomass was chemically treated to modify the functional carboxyl, amino and phosphate groups. These modifications were examined by means of infrared spectroscopy. It was found that an esterification of the carboxyl groups and phosphate and a methylation of the amine groups significantly decreased the biosorption of the heavy metals studied. Thus, the carboxylate, amine and phosphate groups were recognized as important in the biosorption of metal ions by M. rouxii biomass. The role the lipids fraction play was not significant. The study showed that Na, K, Ca and Mg ions were released from the biomass after biosorption of Pb, Cd, Ni and Zn, indicating that ion exchange was a key mechanism in the biosorption of metal ions by M. rouxii biomass.     

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.     

Increased metal tolerance and bioaccumulation of zinc and cadmium in Chlamydomonas reinhardtii expressing a AtHMA4 C-terminal domain protein

The use of microalgal biomass for metal pollutant bioremediation might be improved by genetic engineering to modify the selectivity or capacity of metal biosorption. A plant cadmium (Cd) and zinc (Zn) transporter (AtHMA4) was used as a transgene to increase the ability of Chlamydomonas reinhardtii to tolerate 0.2 mM Cd and 0.3 mM Zn exposure. The transgenic cells showed increased accumulation and internalization of both metals compared to wild-type. AtHMA4 was expressed either as the full-length (FL) protein or just the C-terminal (CT) tail, which is known to have metal-binding sites. Similar Cd and Zn tolerance and accumulation was observed with expression of either the FL protein or CT domain, suggesting that enhanced metal tolerance was mainly due to increased metal binding rather than metal transport. The effectiveness of the transgenic cells was further examined by immobilization in calcium alginate to generate microalgal beads that could be added to a metal contaminated solution. Immobilization maintained metal tolerance, while AtHMA4-expressing cells in alginate showed a concentration-dependent increase in metal biosorption that was significantly greater than alginate beads composed of wild-type cells. This demonstrates that expressing AtHMA4 FL or CT has great potential as a strategy for bioremediation using microalgal biomass.     

The influence of a specific microelemental environment in alginate gel beads on the course of propionic acid fermentation

In this work the exchange of calcium, cobalt, iron, magnesium, zinc and manganese ions between alginate gel beads and casein medium was investigated. The high release of calcium ions from alginate to the medium and the biosorption of some metal ions were observed. The pure alginate gel adsorbed all the metal ions examined, from a fermentative medium. Gel with immobilized cells of two strains of Propionibacterium freudenreichii subsp. shermanii showed an active ability to adsorb only cobalt, iron and zinc ions. In this way, a special microelemental environment was created in the alginate gel. This resulted in an increase of propionic acid production and a decrease of vitamin B₁₂ biosynthesis. Received: 30 April 1997 / Received revision: 2 July 1997 / Accepted: 4 July 1997     

Lead, copper and zinc biosorption from bicomponent systems modelled by empirical Freundlich isotherm

The biosorption of lead, copper and zinc ions on Rhizopus arrhizus has been studied for three single-component and two binary systems. The equilibrium data have been analysed using the Freundlich adsorption model. The characteristic parameters for the Freundlich adsorption model have been determined and the competition coefficients for the competitive biosorption of Pb(II)-Cu(II) at pH 4.0 and 5.0, and Pb(II)-Zn(II) at pH 5.0 have been calculated. For the individual single-component isotherms, lead has the highest biosorption capacity followed by copper, then zinc. The capacity of lead in the two binary systems is always significantly greater than those of the other metal ions, in agreement with the single-component data. Only a partial selectivity for copper ions has been obtained at pH 4.0. Received: 21 June 1999 / Accepted: 2 November 1999     

Heavy metal removal from aqueous solution by wasted biomass from a combined AS-biofilm process

This study evaluated the capability of metal biosorption by wasted biomass from a combined anaerobic-anoxic-oxic (A2O)-biofilm process with simultaneous nitrogen and phosphorus removal. Zinc, cadmium and nickel were rapidly adsorbed in 20 min by the harvested sludge from a continuous-flow pilot-plant. Biosorption equilibrium was then reached in 6h. The biosorption isotherm showed that metal biosorption behavior had fitted well to the Freundlich isotherm, but not Langmuir isotherm. The capacity constants k of Freundlich model for nickel, zinc and cadmium were 0.471, 0.298 and 0.726, respectively; the affinity constants 1/n were 0.444, 0.722 and 0.718, respectively. The order of metal affinity for the wasted biomass was Zn > Cd > Ni, which was in conformity to the other biosorption results with different biological sludge.     

Equilibrium and kinetic studies on biosorption potential of charophyte biomass to remove heavy metals from synthetic metal solution and municipal wastewater

The risk of heavy metal contamination in domestic water causes serious health and environmental problems. Biosorption has been considered as an efficient and alternative way for treatment of heavy metal–contaminated wastewater. The potentials of dried charophytes, Chara aculeolata and Nitella opaca, to biosorb lead (Pb), cadmium (Cd), and zinc (Zn) from synthetic solutions and municipal wastewater were investigated. The efficiency of metal removal was studied under varied conditions in different sorbent dosages, pH, and contact times. Biosorption isotherm and kinetics were used to clarify heavy metal preference and biosorption mechanism. C. aculeolata and N. opaca performed well in the biosorption of all three metal ions, with preference towards Pb, followed by Cd and Zn, in the single-metal solutions. Pb adsorption onto algal biomass followed first-order rate kinetics (N. opaca) and intraparticle diffusion (C. aculeolata and N. opaca). These results indicated physical adsorption process between Pb ions and both algal biomasses. Cd and Zn biosorption kinetics fitted the second-order rate model, indicating chemical adsorption between metal ions and both algae. The experimental data of three-metal biosorption fitted well to Langmuir isotherm model, suggesting that the metal ion adsorption occurred in a monolayer pattern on a homogeneous surface. C. aculeolata exhibited slightly higher maximum uptake of Pb, Cd, and Zn (105.3 mgPb/g, 23.0 mgCd/g, 15.2 mgZn/g) than did N. opaca (104.2 mgPb/g, 20.5 mgCd/g, 13.4 mgZn/g). In multi-metal solutions, antagonistic effect by metal competition was observed. The ability of charophytes to remove Pb and Zn was high in real municipal water (81–100%). Thus, the charophytic biomass may be considered for the treatment of metal contamination in municipal wastewater.     

Localization effect on the metal biosorption capability of recombinant mammalian and fish metallothioneins in Escherichia coli

In this study, we examined the expression of mammalian and fish metallothioneins (MTs) in Escherichia coli as a strategy to enhance metal biosorption efficiency of bacterial biosorbents for lead (Pb), copper (Cu), cadmium (Cd), and zinc (Zn). In addition, MT proteins were expressed in either the cytoplasmic or periplasmic compartment of host cells to explore the localization effect on metal biosorption. The results showed that MT expression led to a significant increase (5-210%) in overall biosorption efficiency (eta(ads)), especially for biosorption of Cd. The MT-driven improvement in metal biosorption relied more on the increase in the biosorption rates (r(2), a kinetic property) than on the equilibrium biosorption capacities (q(max), a thermodynamic property), despite a 10-45% and 30-80% increase in q(max) of Cd and Zn, respectively. Periplasmic expression of MTs appeared to be more effective in facilitating the metal-binding ability than the cytoplasmlic MT expression. Notably, disparity of the impacts on biosorption ability was observed for the origin of MT proteins, as human MT (MT1A) was the most effective biosorption stimulator compared to MTs originating from mouse (MT1) and fish (OmMT). Moreover, the overall biosorption efficiency (eta(ads)) of the MT-expressing recombinant biosorbents was found to be adsorbate-dependent: the eta(ads) values decreased in the order of Cd > Cu > Zn > Pb.     

Biosorbents for recovery of metals from industrial solutions

Summary Biosorbent materials are a potential alternative to conventional processes of metal recovery from industrial solutions. Algal biomass ofSargassum natans andAscophyllum nodosum outperformed ion exchange resins in sequestering respectively gold and cobalt from solutions. Non-living biomass ofSaccharomyces cerevisiae andRhizopus arrhizus exhibited higher metal-uptake capacity than the living biomass for the uptake of copper, zinc, cadmium, uranium. The solution pH affected the metal-uptake capacity of the biomass whereas the equilibrium biosorption isotherms were independent of the initial concentration of the metal in the solution. Desorption of the metal from the biosorbent and recycle of the biosorbent have also been demonstrated.     

Influence of anoxic selectors on heavy metal removal by activated sludge

The goal of this research is to compare the metal binding characteristics of an anoxic selector activated sludge system and a conventional activated sludge system. Metal biosorption by biomass harvested from experimental systems was determined by a series of batch experiments. Heavy metals studied in this research were zinc, cadmium, and nickel. The sorption isotherm showed that the selector sludge had significantly higher sorption capacity than did the control sludge. Metal biosorption behavior closely followed a Freundlich isotherm model for equilibrium concentrations. ECP contents of biomass estimated by alkali extraction technique showed that ECP levels in the selector sludge significantly higher than that in the sludge harvested from the conventional system, indicating that the higher metal sorption capacity of selector sludge may be due to the selection of the ECP-producing bacteria (i.e., Zoogloca sp.) by the selector system.     

Biosorption of Pb(II) and Cu(II) by activated sludge in batch and continuous-flow stirred reactors

Biosorption of Pb(II) and Cu(II) ions in single component and binary systems was studied using activated sludge in batch and continuous-flow stirred reactors. In biosorption experiments, the activated sludge in three different phases of the growth period was used: growing cells; resting cells; dead or dried cells. Because of the low adsorption capacity of the non-viable activated sludge especially in the case of Pb(II) ions, biosorption of the Cu(II) and Pb(II) ions from the binary mixtures was carried out by using the resting cells. The biosorption data fitted better with the Freundlich adsorption isotherm model. Using a mathematical model based on continuous system mass balance for the liquid phase and batch system mass balance for the solid phase, the forward rate constants for biosorption of Pb(II) and Cu(II) ions were 0.793 and 0.242 1 (mmolmin)(-1), respectively.     

Cadmium biosorption by a cadmium resistant strain of Bacillus thuringiensis: regulation and optimization of cell surface affinity for metal cations

A marine bacterial strain putatively identified asBacillus thuringiensis strain DM55, showed multiple heavy metal resistance and biosorption phenotypes. Electron microscopic studies revealed that DM55 cells are encased in anionic cell wall polymers that can immobilize discrete aggregates of cations. Factors affecting cell surface affinity for metal cations, monitored by means of Cd²⁺ binding capability, are investigated. The mechanisms of cadmium resistance and Cd²⁺ biosorption by the bacterium appeared to be inducible and coincident. Medium components affecting metal removal under cadmium-stressed growth conditions were explored based on the application of two sequential multi-factorial statistical designs. Concentrations of potassium phosphates and peptone were the most significant variables. Optimized culture conditions allowed DM55 cells grown in the presence of 0.25 mM CdCl₂ to remove about 79% of the metal ions within 24 h with a specific biosorption capacity of 21.57 mg g^–1 of biomass. Both fresh and dry cells of DM55 prepared under cadmium-free optimal nutrient condition were also able to biosorb Cd²⁺. In addition to the concentration of phosphate in the medium, KinA, a major phosphate provider in the phosphorelay of Bacillus cells, was also demonstrated to regulate the magnitude of cell surface affinity for cadmium ions.     

Zinc exchange by blood cells in nearly physiologic standard conditions

Determination of zinc concentrations in white blood cells has been used to establish zinc deficiency. During pathological conditions changes in zinc concentrations in these blood cells were observed. However, these investigations were hampered by the low amount of zinc in this form per mL blood. Earlier we demonstrated that, in the case of zinc deficiency, the uptake of zinc was increased, using the in vitro exchange of zinc by the various blood cells with extracellular zinc labeled with⁶⁵Zn in fairly physiologic conditions. In case of inflammation, no increase in zinc uptake by erythrocytes was seen, indicating that this method probably can be used to differentiate real from apparent zinc deficiency. Only during the first days of the inflammatory process, probably representing the redistribution phase during which zinc moves from the serum to the liver, a small increase in in vitro zinc uptake was seen in mononuclear cells (MNC) and polymorphonuclear cells (PMNC). Earlier papers raised some questions; e.g., is the uptake part of an exchange process and can the efflux of zinc by the cells be measured by the same method; what is the influence of time on the process of zinc uptake; what is the magnitude of the uptake of zinc by the cells compared to the zinc concentration in the cells; and, what is the influence of temperature on the uptake of zinc? In the present study, the influence of incubation time and temperature on the uptake of zinc by human and rat blood cells and on the release of zinc by rat blood cells was studied. At least three phases of uptake of zinc in the various cells were found by varying the incubation time—a fast phase during the first half hour, probably caused by an aspecific binding of zinc on or in the cell membrane; a second fast uptake between 60–330 min, probably caused by an influx of zinc in the cell as part of the exchange process of zinc; and a slow third phase after 5.5 h, in which probably the in- and efflux of the rapidly exchangeable intracellular pool is more or less equilibrated. For mononuclear cells, polymorphonuclear cells, and erythrocytes of rats, the rapidly exchangeable intracellular pool is 40%, 53%, and 10%, respectively, of the total zinc content of the cells. This study is also performed in human cells; in human cells the exchangeable pool of mononuclear cells and erythrocytes is 17 and 3.5% of the total zinc content of the cells, respectively. The efflux of zinc by blood cells can be measured by the same method. Both the uptake and the loss of zinc by blood cells of rats were compared and are of the same magnitude, indicating that the in vitro uptake of zinc described elsewhere is part of an exchange process. Increasing temperature during incubation procedures results in an increase of zinc uptake by human blood cells, even at high temperatures of 41°C, although there are gradual differences between the various blood cells. Both the in- and efflux of zinc by blood cells are very small at 4°C.     

Biosorption of zinc by fungal mycelial wastes

Summary Waste mycelia from several industrial fermentation plants (Aspergillus niger, Penicillium chrysogenum, Claviceps paspali) were used as a biosorbent for zinc ions from aqueous environments, both batchwise as well as in a column mode. With all mycelia testes, biosorption per biomass dry weight was a function of pH (increasing with increasing pH between 1.0 and 9.0), biomass concentration (decreasing at high biomass concentrations) and the zinc concentration. Under optimized conditions, A. niger and C. paspali were superior to P. chrysogenum. Treatment of A. niger biomass with NaOH further increased its biosorbent capacity. Desorption of biosorbed zinc was achieved by elution with 0.1 m HCl, best results being obtained with NaOH-treated A. niger. Such treatment did not affect the capacity for biosorption in repeated experiments. NaOH-treated A. niger mycelia were also successfully used in removal of zinc from polluted waters in Austria, thereby showing that the simultaneous presence of other naturally occurring ions does not affect biosorption. Offprint requests to: C. P. Kubicek     

The effects of copper and zinc on <Emphasis Type="Italic">Spirulina platensis</Emphasis> growth and heavy metal accumulation in its cells

The effects of copper and zinc on Spirulina platensis (Nordst.) Geitl. growth and the capability of this cyanobacterium for accumulation of these heavy metals (HMs) were studied. S. platensis tolerance to HMs was shown to depend on the culture growth phase. When copper was added during the lag phase, its lethal concentration was 5 mg/l, whereas 4 mg/l were lethal during the linear growth phase. Zinc concentration of 8.8 mg/l was lethal during the linear but not lag phase of growth. HM-treated S. platensis cells were capable for accumulation of tenfold more copper and zinc than control cells. Independently of Cu²⁺ content in the medium and of the growth phase, cell cultures accumulated the highest amount of this metal as soon as after 1 h, which may be partially determined by its primary sorption by cell-wall polysaccharides. A subsequent substantial decrease in the intracellular copper content occurred due to it secretion, which was evident from the increased metal concentration in the culturing medium. When zinc was added during the linear growth phase, similar pattern of its accumulation was observed: the highest content after 1 h and its subsequent decrease to the initial level. When the initial density of the culture was low and the cells had much time to adapt to HM, zinc accumulated during the entire linear growth phase, and thereafter the metal was secreted to the medium. The mechanisms of S. platensis tolerance to HM related to both their sorption by the cell walls and secretion of metal excess into the culturing medium and its conversion into the form inaccessible for the cells are discussed.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 259–265.Original Russian Text Copyright © 2005 by Nalimova, Popova, Tsoglin, Pronina.This revised version was published online in April 2005 with a corrected cover date.     

Zn2+ biosorption by Oscillatoria anguistissima

Oscillatoria anguistissima showed a very high capacity for Zn²⁺ biosorption (641 mg g⁻¹ dry biomass at a residual concentration of 129·2 ppm) from solution and was comparable to the commmercial ion-exchange resin IRA-400C. Zn²⁺ biosorption was rapid, pH dependent and temperature independent phenomenon. Zn²⁺ adsorption followed both Langmuir and Freundlich models. The specific uptake (mg g⁻¹ dry biomass) of metal decreased with increase in biomass concentration. Pretreatment of biomass did not significantly affect the biosorption capacity of O. anguistissima. The biosorption of zinc by O. anguistissima was an ion-exchange phenomenon as a large concentration of magnesium ions were released during zinc adsorption. The zinc bound to the biomass could be effectively stripped using EDTA (10 mM) and the biomass was effectively used for multiple sorption–desorption cycles with in-between charging of the biomass with tap water washings. The native biomass could also efficiently remove zinc from effluents obtained from Indian mining industries.     

Biosorption of nickel (II) from effluent of electroplating industry by immobilized cells of Bacillus species

In this study, Ni (II) biosorption capacity of immobilized cells of Bacillus sp. was investigated. Biosorption of Ni (II) was carried out in batch experiments and the important environmental conditions were optimized. The uptake of metal was rapid, and equilibrium was attained within 270 min. Bacillus strains (ten cultures) were isolated from nickel electroplating effluent by heat shock method. These isolates were grown up in nutrient broth supplemented with Ni (II)(50 mg/L). The culture, exhibiting maximum biosorption capacity (q^max: 118 mg/g), was selected and labeled Bacillus Bio‐4. In order to develop an economical biosorption process cell mass of Bacillus, Bio‐4 was immobilized in Na‐alginate. It was concluded from the results that biosorption of nickel is highly dependent on the type of sorbent and experimental conditions employed. Our results demonstrate that 6.0 mg immobilized cells (18 mg cell biomass in 3.0 mL of 1% Na alginate) had a maximum biosorption capacity of 113 mg Ni(II) per liter of suspension at pH 8.0, 100 rpm and 25°C. The Ni (II) removal was estimated to be 97.4%.     

Zinc biosorption from aqueous solution by a halotolerant cyanobacterium Aphanothece halophytica

We have investigated the characteristics of zinc biosorption by Aphanothece halophytica. Zinc could be rapidly taken up from aqueous solution by the cells with an equilibrium being reached within 15 min of incubation with 100 mg L⁻¹ ZnCl₂. The adsorbed zinc was desorbed by treatment with 10 mM EDTA. The presence of glucose, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and N,N′-dicyclohexylcarbodiimide (DCCD) did not affect the uptake of zinc. The specific uptake of zinc increased at low cell concentration and decreased when cell concentration exceeded 0.2 g L⁻¹. The binding of zinc followed Langmuir isotherm kinetics with a maximum zinc binding capacity of 133 mg g⁻¹ and an apparent zinc binding constant of 28 mg L⁻¹. The presence of an equimolar concentration of Mn²⁺, Mg²⁺, Co²⁺, K⁺, or Na⁺ had no effect on zinc biosorption, whereas Ca²⁺, Hg²⁺, and Pb²⁺ showed an inhibitory effect. The biosorption of zinc was low at a pH range from 4 to 6, but increased progressively at pH 6.5 and 7. Received: 12 December 2001 / Accepted: 11 January 2002     

Differential pulse polarography: a method for the direct study of biosorption of metal ions by live bacteria from mixed metal solutions

The technique of differential pulse polarography is shown here to be applicable to the monitoring directly the biosorption of metal ions from solution by live bacteria from mixed metal solutions. Biosorption of Cd(II), Zn(II) and Ni(II) by P. cepacia was followed using data obtained at the potential which is characteristic of the metal ion in the absence and presence of cells. Hepes buffer (pH 7.4, 50 mM) was used as a supporting electrolyte in the polarographic chamber and metal ion peaks in the presence of cells of lower amplitude were obtained due to metal-binding by the cells. Well defined polarographic peaks were obtained in experiments involving mixtures of metal ions of Cd(II)-Zn(II), Cu(II)-Zn(II), Cu(II)-Cd(II) and Cd(II)-Ni(II). Biosorption of Cd(II), Zn(II) increased with solution pH. The method was also tested as a rapid technique for assessing removal of metal ions by live bacteria and the ability of the polarographic technique in measuring biosorption of metal ions from mixed metal solutions is demonstrated. Cu(II) was preferentially bound and removal of metals was in the order Cu(II) > Ni(II) > Zn(II), Cd(II) by intact cells of P. cepacia. This revised version was published online in August 2006 with corrections to the Cover Date.