Biosorption of copper and zinc by Cymodocea nodosa

Long-term sediment records reveal over three thousand years of heavy metal inputs in the Mar Menor coastal lagoon (SE Spain)

The Mar Menor lagoon combined high biological production and environmental quality, making it an important economic engine. However, the pressure of human activities put its ecological integrity at risk, the oldest environmental impact being mining activity recorded since Roman times, about 3500 years ago, reaching its maximum intensity in the 20th century, contributing heavy metals to the lagoon sediments for almost 30 centuries. This work reviews the spatiotemporal evolution of the main heavy metals in this coastal lagoon using data from 272 surface sediment samples obtained during the last 40 years and two deep cores covering the total history of the lagoon (c. 6500 yrs BP), so as their incidence in the lagoon trophic web. The observed patterns in sedimentation, sediment characteristics and heavy metal content respond to the complex interaction, sometimes synergistic and sometimes opposing, between climatic conditions, biological production and human activities, with mining being mainly responsible for Pb, Zn and Cd inputs and port activities for Cu. High Fe/Al, Ti/Al and Zr/Al ratios identify periods of mining activity, while periods of arid climatic conditions and deforestation that increase erosion processes in the drainage basin and silt concentration in the lagoon sediments are determined by high Zr/Rb and, to a lesser extent, Zr/Al and Si/Al ratios. After the cessation of direct discharges into the lagoon in the 1950s, the recent evolution of heavy metals concentration and its spatial redistribution would be determined by hydrographic and biogeochemical processes, solubility of different elements, and coastal works in harbours and on beaches. The bioconcentration factor decreases along the trophic levels of the food web, suggesting that the lagoon ecosystem provides an important service by retaining heavy metals in the sediment, largely preventing their bioavailability, but actions involving resuspension or changes in sediment conditions would pose a risk to organisms.

Valorization of Sargassum Biomass as Potential Material for the Remediation of Heavy-Metals-Contaminated Waters

Sargassum algae has become a major environmental issue due to its abundance in the Pacific Ocean with hundreds of tons reaching the beaches of the Mexican Caribbean every year. This generates large quantities of decomposing organic matter that have a negative impact on the region's economy and ecosystems. Sargassum valorization has turned out to be a fundamental aspect to mitigate its environmental impact. This study proposes the use and application of untreated Sargassum biomass for the decontamination of waters polluted with lead (Pb) and cadmium (Cd) through single and binary adsorption tests. Physicochemical and textural properties examined by SEM, XRD, and FT-IR elucidated that Sargassum biomass is viable to be used as a potential environmental benign adsorbent, exhibiting Cd(II) and Pb(II) adsorption capacities as high as 240 mg g-1 and 350 mg g-1, respectively, outperforming conventionally used adsorbents. This is attributed to its morphology, favorable surface charge distribution, and the presence of -OH and -COH groups. A strong affinity between the biomass and metal pollutants was evidenced by a thermodynamics study, showing a spontaneous and endothermic process. This work sets a practical route for the utilization of the Sargassum biomass, demonstrating its applicability as a potential material for heavy-metal-polluted water remediation, making a substantial contribution to a circular economy system.

Phytoremediation of Heavy Metals: An Indispensable Contrivance in Green Remediation Technology

Environmental contamination is triggered by various anthropogenic activities, such as using pesticides, toxic chemicals, industrial effluents, and metals. Pollution not only affects both lotic and lentic environments but also terrestrial habitats, substantially endangering plants, animals, and human wellbeing. The traditional techniques used to eradicate the pollutants from soil and water are considered expensive, environmentally harmful and, typically, inefficacious. Thus, to abate the detrimental consequences of heavy metals, phytoremediation is one of the sustainable options for pollution remediation. The process involved is simple, effective, and economically efficient with large-scale extensive applicability. This green technology and its byproducts have several other essential utilities. Phytoremediation, in principle, utilizes solar energy and has an extraordinary perspective for abating and assembling heavy metals. The technique of phytoremediation has developed in contemporary times as an efficient method and its success depends on plant species selection. Here in this synthesis, we are presenting a scoping review of phytoremediation, its basic principles, techniques, and potential anticipated prospects. Furthermore, a detailed overview pertaining to biochemical aspects, progression of genetic engineering, and the exertion of macrophytes in phytoremediation has been provided. Such a promising technique is economically effective as well as eco-friendly, decontaminating and remediating the pollutants from the biosphere.

Adsorption of indium by waste biomass of brown alga Ascophyllum nodosum

The biosorption capacities of dried meal and a waste product from the processing for biostimulant extract of Ascophyllum nodosum were evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents: waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, and natural-biomass which was harvested, dried and milled as a commercial, "kelp meal" product. Two systems have been evaluated: ideal system with indium only, and double metal-system with indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In the ideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed, waste biomass and 63 mg/g for the natural biomass), than in the double metal-system where the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in the A. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.

The role of Cymodocea nodosa on the dynamics of trace elements in different marine environmental compartments at the Mar Menor Lagoon (Spain)

During mining activities historically developed at Sierra Minera (Cartagena-La Unión, Spain), high amounts of trace elements were discharged to the Mar Menor coastal lagoon mainly through El Beal Wadi. The objective of this study is to establish the role played by the Cymodocea nodosa in the coastal marine dynamics of trace elements at the mouth of the wadi. To this end, the content of nine trace elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in different marine environmental compartments (i.e. marine and coastal sediments, C. nodosa tissues collected from live seagrass and C. nodosa beach cast litter) at two different locations were determined by inductively coupled plasma atomic emission spectrometry. The results showed that the seagrass C. nodosa could mobilise part of the elements present in marine sediments and water, thereby causing their re-accumulation in the coastal sediments through the C. nodosa beach cast litter.

Equilibrium and kinetic studies of copper biosorption by dead Ceriporia lacerata biomass isolated from the litter of an invasive plant in China

BACKGROUND

Ceriporia lacerata, a strain of white-rot fungus isolated from the litter of an invasive plant (Solidago canadensis) in China, was little known about its properties and utilization. In this work, the copper(II) biosorption characteristics of formaldehyde inactivated C. lacerata biomass were examined as a function of initial pH, initial copper(II) concentration and contact time, and the adsorptive equilibrium and kinetics were simulated, too.

RESULTS

The optimum pH was found to be 6.0 at experimental conditions of initial copper(II) concentration 100 mg/L, biomass dose 2 g/L, contact time 12 h, shaking rate 150 r/min and temperature 25°C. Biosorption equilibrium cost about 1 hour at experimental conditions of pH 6.0, initial copper(II) concentration 100 mg/L, C. lacerata dose 2 g/L, shaking rate 150 r/min and temperature 25°C. At optimum pH 6.0, highest copper(II) biosorption amounts were 6.79 and 7.76 mg/g for initial copper(II) concentration of 100 and 200 mg/L, respectively (with other experimental parameters of C. lacerata dose 2 g/L, shaking rate 150 r/min and temperature 25°C). The pseudo second-order adsorptive model gave the best adjustment for copper(II) biosorption kinetics. The equilibrium data fitted very well to both Langmuir and Freundlich adsorptive isotherm models.

CONCLUSIONS

Without further acid or alkali treatment for improving adsorption properties, formaldehyde inactivated C. lacerata biomass possesses good biosorption characteristics on copper(II) removal from aqueous solutions.

Biosorption of zinc from aqueous solution using chemically treated rice husk

In this study, adsorption of zinc onto the adsorbent (untreated rice husk and NaOH-treated rice husk) was examined. During the removal process, batch technique was used, and the effects of pH and contact time were investigated. Langmuir isotherm was applied in order to determine the efficiency of NaOH-treated rice husk used as an adsorbent. The zinc adsorption was fast, and equilibrium was attained within 30 min. The maximum removal ratios of zinc for untreated rice husk and NaOH-treated rice husk after 1.5 h were 52.3% and 95.2%, respectively, with initial zinc concentration of 25 mg/L and optimum pH of 4.0. Data obtained from batch adsorption experiments fitted well with the Langmuir isotherm model. Maximum adsorption capacity of zinc onto untreated rice husk and NaOH-treated rice husk was 12.41 mg/g, and 20.08 mg/g respectively, at adsorbent dosage of 1 g/L at 25°C. The nature of functional groups (i.e., amino, carboxyl, and hydroxyl) and metal ion interactions was examined by the FT-IR technique. It was concluded that the NaOH-treated rice husk had stronger adsorption capacity for Zn(2+) compared with the untreated rice husk. The NaOH-treated rice husk is an inexpensive and environmentally friendly adsorbent for Zn(2+) removal from aqueous solutions.

Phycoremediation of lead and cadmium by employing Nostoc muscorum as biosorbent and optimization of its biosorption potential

The present study reports the influence of different factors on the sorption of Pb and Cd by Nostoc muscorum. The results showed that extent of Pb and Cd removal by N. muscorum cells increased with increasing biosorbent dose, but exhibited decline in the adsorption capacity. The maximum sorption of Cd (85.2%) and Pb (93.3%) was achieved at 60 and 80 microg/ml concentrations of respective metal, within 30 and 15 min, respectively. The result revealed that optimum biosorption of Pb and Cd occurred at pH 5 and 6, respectively, at 40 degrees C temperature. Presence of binary metals (both Pb and Cd) in a solution showed that the presence of one metal ion resulted into decreased sorption of other metal ion. The presence of Ca and EDTA showed significant decrease in the sorption of Pb and Cd, while other anions and cations did not show significant effect on the biosorption of both the metals. Maximum desorption of Pb and Cd was achieved in the presence of EDTA and HNO3, respectively. Results also showed that the test biosorbent could be repeatedly used up to six biosorption/desorption cycles without significant loss of its initial metal adsorption capacity.

Marine macrophytes as effective lead biosorbents

Several species of seagrass and marine macrophytes were investigated for their biosorption performance in the removal of lead from aqueous solution. The effect of pH on the equilibrium of the seagrass Cymodocea nodosa as a biosorbent also was studied. It was found that increasing pH increased lead biosorption, with a maximum uptake of approximately 140 mg/g in the range pH 3.3 to 5. Equilibrium data at different pH levels were successfully fitted to competitive equilibrium models. In addition, the seaweeds belonging to different phyla (i.e., Chlorophyta, Heterokontophyta, and Rhodophyta) were studied for the effect of their structure on equilibrium at a constant pH 5. The brown algae (Heterokontophyta) showed the highest potential for lead sorption, with a maximum uptake of 220 mg/g for C. compressa and 140 mg/g for S. lomentaria. The green algae (Chlorophyta) showed lead uptake in the range 40 to 90 mg/g, and the red algae (Rhodophyta) was least effective, with uptake in the range 10 to 40 mg/g.

Sorption and desorption of Cd, Cu and Pb using biomass from an eutrophized habitat in monometallic and bimetallic systems

This work examines the sorption capacity of a natural biomass collected from an irrigation pond. The biomass mainly consisted of a mixture of chlorophyte algae with caducipholic plants. Biosorption experiments were performed in monometallic and bimetallic solutions containing different metals commonly found in industrial effluents (Cd, Cu and Pb). The biosorption process was slightly slower in the binary system comparing with monometallic system which was related to competition phenomena between metal cations in solution. The biosorbent behaviour was quantified by the sorption isotherms fitting the experimental data to mathematical models. In monometallic systems, the Langmuir model showed a better fit with the following sorption order: Cu ~ Pb > Cd; and biomass-metal affinity order: Pb > Cd ~ Cu. In bimetallic systems, the binary-type Langmuir model was used and the sorption order obtained was: Pb ~ Cu > Cd. In addition, the effectiveness of the biomass was investigated in several sorption-desorption cycles using HCl and NaHCO(3). The recovery of metal was higher with HCl than with NaHCO(3), though the sorption uptake of the biomass was sensitively affected by the former desorption agent in subsequent sorption cycles.

Equilibrium of Cu(II) and Ni(II) biosorption by marine alga Sargassum filipendula in a dynamic system: competitiveness and selectivity

The study focuses on the equilibrium of dynamic biosorption in single and binary systems containing Cu(II) and Ni(II) ions using Sargassum filipendula (a marine alga). The experiments were performed in fixed-bed columns with both single-component and bi-component metal solutions (using different molar concentrations). Experimental data were fitted with different equilibrium models such as Langmuir, Langmuir with inhibition, Jain and Snowyink and Langmuir-Freundlich equations. The biosorption of pure metal ions in solution presented adequate capacities both for Cu(II) and Ni(II). In binary solutions the preferential sorption of Cu(II) over Ni(II) was demonstrated by the displacement of Ni(II) (marked overshoot on the breakthrough curves).

Remoção de Pb(II) de soluções aquosas por Biossorção em R. opacus

Nesse estudo foi avaliada a capacidade de biossorção de íons chumbo em solução aquosa pela bactéria Rhodococcus opacus. Avaliou-se em batelada o efeito do pH da solução, concentração da biomassa, tempo de contato e concentração inicial do metal. A cinética adequou-se melhor ao modelo de pseudo-segunda ordem. Empregaram-se as isotermas de Langmuir e Freundlich para representar o processo de sorção no equilíbrio. O valor da capacidade máxima de captação (q max) obtida pelo modelo de Langmuir foi de 94,34 mg g-1. No ensaio de biossorção competitiva a remoção do chumbo foi afetada pela presença de outros metais na solução.

Study of cadmium, zinc and lead biosorption by orange wastes using the subsequent addition method

The biosorption of several metals (Cd2+, Zn2+ and Pb2+) by orange wastes has been investigated in binary systems. Multicomponent sorption isotherms were obtained using an original procedure, similar to that proposed by Pagnanelli et al. [Pagnanelli, F., Petrangeli, M.P., Toro, L., Trifoni, M., Veglio, F., 2001a. Biosorption of metal ions on Arthrobacter sp.: biomass characterization and biosorption modelling. Environ. Sci. Technol. 34, 2773-2778] for monoelement systems, known as subsequent addition method (SAM). Experimental sorption data were analysed using an extended multicomponent Langmuir equation. The maximum sorption uptake was approximately 0.25mmol/g for the three binary systems studied. The reliability of the proposed procedure for obtaining the equilibrium data in binary systems was verified by means of a statistical F-test.

Sorption of lead, mercury and cadmium ions in multi-component system using carbon aerogel as adsorbent

In the present study, adsorption of three metal ions Pb(II), Hg(II) and Cd(II) on carbon aerogel a new form of activated carbon has been investigated in mono- and multi-component (binary and tertiary) system. Batch experiments were also carried out for mono- and multi-component systems with varying metal ion concentration (mg/l) to investigate the competitive adsorption characteristics. Many adsorbents have been studied for their adsorption properties pertaining to mono-component solutions of metal ions. However, to treat wastewater with new materials, their performance needs to be ascertained in multi-component system. The scanning electron micrographs (SEM) and EDAX spectrum of carbon aerogel surfaces before and after the adsorbent was equilibrated with the metal ion solution clearly establishes the presence of the metal ions and some surface modifications can be observed on the carbon aerogel particles adsorption with (i) surface chemistry of the pellets on the surface of carbon aerogel and (ii) inside layers of the carbon aerogel. Applicability of the isotherm models namely Freundlich and Langmuir to predict the equilibrium uptake of Pb(II), Hg(II) and Cd(II) in mono-component, binary and tertiary system has also been tested. Langmuir and Freundlich models are found to generally represent the experimental though but not consistently.

Biosorption characteristics of copper (II), chromium (III), nickel (II), and lead (II) from aqueous solutions by Chara sp. and Cladophora sp

The aim of this research was to expose individual removals of copper, chromium, nickel, and lead from aqueous solutions via biosorption using nonliving algae species, Chara sp. and Cladophora sp. Optimum pH values for biosorption of copper (II), chromium (III), nickel (II), and lead (II) from aqueous solutions were determined to be 6, 7, 7, and 3 for Cladophora sp. and 5, 3, 5, and 4 for Chara sp. respectively. Maximum adsorption capacities of Chara sp. [10.54 for chromium (III) and 61.72 for lead (II)] and Cladophora sp. [6.59 for chromium (III) and 16.75 and 23.25 for lead (II)] for chromium (III) and lead (II) are similar. On the other hand, copper (II) and nickel (II) biosorption capacity of Cladophora sp. [14.28 for copper (II) and 16.75 for nickel (II)] is greater than Chara sp. [6.506 for copper (II) and 11.76 for nickel (II)]. Significantly high correlation coefficients indicated for the Langmuir adsorption isotherm models can be used to describe the equilibrium behavior of copper, chromium, nickel, and lead adsorption onto Cladophora sp. and Chara sp.

Sorption and desorption of lead (II) from wastewater by green algae Cladophora fascicularis

Biosorption is an effective method to remove heavy metals from wastewater. In this work, adsorption features of Cladophora fascicularis were investigated as a function of time, initial pH, initial Pb(II) concentrations, temperature and co-existing ions. Kinetics and equilibria were obtained from batch experiments. The biosorption kinetics followed the pseudo-second order model. Adsorption equilibria were well described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 198.5 mg/g at 298K and pH 5.0. The adsorption processes were endothermic and the biosorption heat was 29.6 kJ/mol. Desorption experiments indicated that 0.01 mol/L Na(2)EDTA was an efficient desorbent for the recovery of Pb(II) from biomass. IR spectrum analysis suggested amido or hydroxy, CO and C-O could combine intensively with Pb(II).

Biosorption of Cu2+, Cd2+, Pb2+, and Zn2+ using dried marine green macroalga Caulerpa lentillifera

The sorption of Cu2+, Cd2+, Pb2+, and Zn2+ by a dried green macroalga Caulerpa lentillifera was investigated. The removal efficiency increased with pH. The analysis with FT-IR indicated that possible functional groups involved in metal sorption by this alga were O-H bending, N-H bending, N-H stretching, C-N stretching, C-O, SO stretching, and S-O stretching. The sorption of all metal ions rapidly reached equilibrium within 20min. The sorption kinetics of these metals were governed by external mass transfer and intraparticle diffusion processes. The sorption isotherm followed the Langmuir isotherm where the maximum sorption capacities was Pb2+>Cu2+>Cd2+>Zn2+.

Biosorption characteristics of Aspergillus flavus biomass for removal of Pb(II) and Cu(II) ions from an aqueous solution

The Pb(II) and Cu(II) biosorption characteristics of Aspergillus flavus fungal biomass were examined as a function of initial pH, contact time and initial metal ion concentration. Heat inactivated (killed) biomass was used in the determination of optimum conditions before investigating the performance of pretreated biosorbent. The maximum biosorption values were found to be 13.46 +/- 0.99 mg/g for Pb(II) and 10.82 +/- 1.46 mg/g for Cu(II) at pH 5.0 +/- 0.1 with an equilibrium time of 2 h. Detergent, sodium hydroxide and dimethyl sulfoxide pretreatments enhanced the biosorption capacity of biomass in comparison with the heat inactivated biomass. The biosorption data obtained under the optimum conditions were well described by the Freundlich isotherm model. Competitive biosorption of Pb(II) and Cu(II) ions was also investigated to determine the selectivity of the biomass. The results indicated that A. flavus is a suitable biosorbent for the removal of Pb(II) and Cu(II) ions from aqueous solution.

Biosorption of Au (III) and Cu (II) from Aqueous Solution by a Non-LivingCetraria Islandica (L.) Ach

Biosorption of Au(III) and Cu(II) from dilute aqueous solutions was investigated by biomass of the non-living Cetraria islandica (L.) Ach. The removal and recovery of gold and copper were studied by applying batch technique. The experimental parameters such as the pH of the solution, contact time, the amount of Cetraria islandica (L.) Ach. (dried lichen), the concentration of metals on retention and eluents kind and amount have been investigated. Au(III) and Cu(II) were adsorbed on the dried lichen at pH 3 and pH 8, respectively. Quantitative retention (> or = 90%) was obtained within 60 minutes for metals. Maximum capacity of 1.0 g of dried lichen for biosorption of Au(III) and Cu(II) were found as 7.4 mg of Au(III) and 19.2 mg of Cu(II). It was seen that the adsorption equilibrium data conformed well to the Langmuir model and Freundlich equation for Au(III) and only Freundlich equation for Cu(II). The method proposed in this study was applied to spiked mineral water analysis and metals adsorbed on the lichens were quantitatively (> or = 90%) recovered from mineral water samples by using 0.5 mol L(-1) HCl.

The combined effects of zinc and alga on the life table demography of Anuraeopsis fissa and Brachionus rubens (Rotifera)

In this work the combined effects of zinc and Chlorella on the demography of two co-occurring planktonic rotifers (A. fissa and B. rubens) were evaluated. Chlorella absorbed a significant (about 35%) quantity of zinc from the medium within the 24 h period. The age-specific survivorship curves of A. fissa and B. rubens showed increased mortality rate with increasing zinc concentration in the medium (0 to 0.5 mg L(-1)), at the two Chlorella levels (0.5 x 10(6) and 1.0 x 10(6) cells mL(-1)). In controls, both the rotifer species showed enhanced survival at higher food level (1.0 x 10(6) cells mL(-1)). Low food level (0.5 x 10(6) cells mL(-1)) and higher concentration (0.25 and 0.5 mg L(-1)) of zinc resulted in a steep fall in the survivorship. Regardless of Zn concentration and food level, A. fissa had a shorter average lifespan, lower gross and net reproductive rate, and rate of population increase than B. rubens. The maximum offspring production on a given day in controls for A. fissa was about 2 female(-1), which was reduced to half when exposed to 0.5 mg L(-1) of Zn. At both food levels, A. fissa exposed to Zn at 0.5 mg L(-1) had negative population growth rates. The highest population growth rate (0.94 day(-1)) was observed for B. rubens in controls at 1.0 x 10(6) cell mL(-1) of Chlorella. The present data showed that A. fissa was more sensitive to zinc toxicity than B. rubens. Combination of high vulnerability to metal toxicity and low population growth rate, A. fissa in zinc contaminated waterbodies could be possibly more adversely affected than B. rubens.

The use of waste biomass of Sargassum sp. for the biosorption of copper from simulated semiconductor effluents

Seaweed Sargassum sp. biomass proved to be useful for the recovery of ionic copper from highly concentrated solutions simulating effluents from semiconductor production. In the case of solutions containing copper in the form of chloride, sulphate and nitrate salts, the best pH for the recovery of copper was 4.5. It was observed that copper biosorption from copper nitrate solutions was higher than the recovery of copper from copper chloride or sulphate solutions. The continuous system used was constituted of four column reactors filled with the biomass of Sargassum sp. and showed high operational stability. Biomass of Sargassum sp. in the reactors was gradually saturated from the bottom to the top of each column reactor. The biomass of Sargassum sp. in the first column was saturated first, followed by a gradual saturation of the remaining columns due to the pre-concentration caused by the biomass in the first column. The biomass of Sargassum in the bioreactors completely biosorbed the ionic copper contained in 63 L of copper sulphate solution, 72 L of copper chloride solution and 72 L of copper nitrate solution, all the solutions containing copper at 500 mg/L. Effluents produced after biosorption presented copper concentrations less than 0.5 mg/L.

The removal of Cu(II) from aqueous solutions by Ulothrix zonata

In this work, adsorption of copper(II) ions on alga has been studied by using batch adsorption techniques. The equilibrium biosorption level was determined as a function of contact time at several initial metal ion concentrations. The effect of adsorbent concentration on the amount adsorbed was also investigated. The experimental adsorption data were fitted to the Langmuir adsorption model. The free energy change (deltaG0) for the adsorption process was found to be -12.60 kJ/mol. The results indicated that the biomass of Ulothrix zonata is a suitable biosorbent for both the removal and recovery of heavy metals from wastewater.

Treatment of simulated Reactive Yellow 22 (azo) dye effluents using Spirogyra species

The potential of commonly available green algae belonging to Spirogyra species was investigated as viable biomaterials for biological treatment of simulated synthetic azo dye (Reactive Yellow 22) effluents. The results obtained from the batch experiments revealed the ability of the algal species in removing the dye colour and was dependent both on the dye concentration and algal biomass. Maximum dye colour removal was observed on the third day for all the system conditions. Monitoring of ORP values helped to understand the overlying biochemical mechanism of algal-dye system. Based upon the results, the dye-algal treatment mechanism was attributed to biosorption (sorption of dye molecules over the surface of algal cells), bioconversion (diffusion of dye molecules into the algal cells and subsequent conversion) and biocoagulation (coagulation of dye molecules present in the aqueous phase onto the biopolymers released as metabolic intermediates during metabolic conversion of dye and subsequent settlement).

Novel Zn(2+)-chelating peptides selected from a fimbria-displayed random peptide library

The display of peptide sequences on the surface of bacteria is a technology that offers exciting applications in biotechnology and medical research. Type 1 fimbriae are surface organelles of Escherichia coli which mediate D-mannose-sensitive binding to different host surfaces by virtue of the FimH adhesin. FimH is a component of the fimbrial organelle that can accommodate and display a diverse range of peptide sequences on the E. coli cell surface. In this study we have constructed a random peptide library in FimH. The library, consisting of approximately 40 million individual clones, was screened for peptide sequences that conferred on recombinant cells the ability to bind Zn(2+). By serial selection, sequences that exhibited various degrees of binding affinity and specificity toward Zn(2+) were enriched. None of the isolated sequences showed similarity to known Zn(2+)-binding proteins, indicating that completely novel Zn(2+)-binding peptide sequences had been isolated. By changing the protein scaffold system, we demonstrated that the Zn(2+)-binding seems to be uniquely mediated by the peptide insert and to be independent of the sequence of the carrier protein. These findings might be applied in the design of biomatrices for bioremediation purposes or in the development of sensors for detection of heavy metals.

Aspergillus niger absorbs copper and zinc from swine wastewater

Wastewater from swine confined-housing operations contains elevated levels of copper and zinc due to their abundance in feed. These metals may accumulate to phytotoxic levels in some agricultural soils of North Carolina due to land application of treated swine effluent. We evaluated fungi for their ability to remove these metals from wastewater and found Aspergillus niger best suited for this purpose. A. niger was able to grow on plates amended with copper at a level five times that inhibitory to the growth of Saccharomyes cerevisiae. We also found evidence for internal absorption as the mechanism used by A. niger to detoxify its environment of copper, a property of the fungus that has not been previously exploited for metal bioremediation. In this report, we show that A. niger is capable of removing 91% of the copper and 70% of the zinc from treated swine effluent.