Biosorption of uranium(VI) by Aspergillus fumigatus

Aspergillus fumigatus removed uranium(VI) very rapidly and reached equilibrium within 1 h of contact of biomass with the aqueous metal solution. Biosorption data fitted to Langmuir model of isotherm and a maximum loading capacity of 423 mg U g^–1 dry wt was obtained. Distribution coefficient as high as 10,000 (mg U g^–1)/(mg U ml^–1) at a residual metal ion concentration of 19 mg l^–1 indicates its usefulness in removal of uranium(VI) from dilute waste streams. Optimum biosorption was seen at pH 5.0 and was independent of temperature (5–50°C ). Initial metal ion concentration significantly influenced uptake capacity which brought down % (w/w) uranium(VI) removal from 90 at 200 mg U l^–1 to 35 at 1000 mg U l^–1. Presence of 0.84 mmol Fe²⁺, Fe³⁺, Ca²⁺ and Zn²⁺ had no effect on uranium(VI) biosorption unlike Al³⁺ (0.84 mM) which was inhibitory.     

Characterization of cadmium removal by Rhodotorula sp. Y11

Experiments were conducted studying the removal of Cd²⁺ from water via biosorption using Rhodotorula sp. Y11. The effects of temperature and initial pH of the solution on biosorption were studied. Caustic and heat treatments showed different influences on the biosorption capacity, and the highest metal uptake value (19.38 mg g⁻¹) was obtained by boiling treated yeast cells. The presence of competing cations, such as Ag⁺, Cu²⁺, and Mg²⁺, except Na⁺ ions, significantly interfered with the metal uptake. Results indicate that the Langmuir model gave a better fit to the experimental data than the Freundlich equation. The q ₁₀ value was 11.38 mg g⁻¹ for Cd²⁺ uptake by Y11. Chemical modifications of the biomass demonstrated that carboxyl and amide groups play an important role in Cd²⁺ biosorption.     

Biosorption of metal ions byAzotobacter vinelandii

Azotobacter vinelandii was better than eitherDerxia gummosa orRhizobium trifolii for sorption of UO ₂ ²⁺ . Its maximum binding capacity was 0.25 mmol UO ₂ ²⁺ /g dry biomass with an affinity constant of 333 l/mmol at pH 4.1 according to the Langmuir model. In a semisynthetic medium,A. vinelandii showed the highest sorption capacity in the early stationary phase. The binding of UO ₂ ²⁺ , Cu²⁺, Ca²⁺ and Zn²⁺ was affected by the pH of the solution. With HCl as eluent, virtually all the sorbed UO ₂ ²⁺ was released. The presence of Cu²⁺, Cd²⁺, Ca²⁺, and Zn²⁺ inhibited the UO ₂ ²⁺ biosorption whereas Mg²⁺ and K⁺ had no effect.     

Effect of salinity and pH on cobalt biosorption by the estuarine microalgaChlorella saliva

Summary Accumulation of cobalt (⁶⁰Co) by the estuarine microalgaChlorella salina has been characterized. At cobalt concentrations ranging over 3.125–100 M, a significant amount of cobalt was bound within 1 min. This was metabolism-independent and unaffected by incubation in light or dark conditions. This initial rapid phase of biosorption was followed by a slower phase of uptake which was apparently active and inhibited by incubation in the dark, or by the uncoupler dinitrophenol and the respiratory and photosynthetic inhibitor potassium cyanide in the light. For cells suspended in 10 mM Taps pH 8, cobalt biosorption followed a Freundlich adsorption isotherm. However, in the presence of 0.5 M NaCl, biosorption deviated from the Freundlich model because of competition by Na⁺. Cobalt biosorption was decreased by increasing concentrations of Na⁺, decreasing pH and the presence of Cs⁺, Li⁺, Rb⁺, Zn²⁺. Mn²⁺ and Sr²⁺ (added as chlorides). This was a result of competition between Co²⁺ and the other cations, including H⁺, for available binding sites on the cell wall and was confirmed by increased desorption of cobalt by solutions of low pH or high salinity. Increasing cell density resulted in increased removal of cobalt from solution but decreased the specific amount of cobalt taken up by the cells.     

Purification and characterisation of two extremely halotolerant xylanases from a novel halophilic bacterium

The present work reports for the first time the purification and characterisation of two extremely halotolerant endo-xylanases from a novel halophilic bacterium, strain CL8. Purification of the two xylanases, Xyl 1 and 2, was achieved by anion exchange and hydrophobic interaction chromatography. The enzymes had relative molecular masses of 43 kDa and 62 kDa and pI of 5.0 and 3.4 respectively. Stimulation of activity by Ca²⁺, Mn²⁺, Mg²⁺, Ba²⁺, Li²⁺, NaN₃ and isopropanol was observed. The K_m and V_max values determined for Xyl 1 with 4-O-methyl-d-glucuronoxylan are 5 mg/ml and 125,000 nkat/mg respectively. The corresponding values for Xyl 2 were 1 mg/ml and 143,000 nkat/mg protein. Xylobiose and xylotriose were the major end products for both endoxylanases. The xylanases were stable at pH 4–11 showing pH optima around pH 6. Xyl 1 shows maximal activity at 60°C, Xyl 2 at 65°C (at 4 M NaCl). The xylanases showed high temperature stability with half-lives at 60°C of 97 min and 192 min respectively. Both xylanases showed optimal activity at 1 M NaCl, but substantial activity remained for both enzymes at 5 M NaCl.Communicated by W.D. Grant     

Repeated removal of cadmium and zinc from an industrial effluent by waste biomass Sargassum sp.

Waste biomass Sargassum sp. biosorbed 100% of Cd²⁺ and 99.4% of Zn²⁺ from a 3 and 98 mg l^–1 solution (pH 4.5), respectively, at the end of four serial experiments. Of the five desorbents studied in consecutive adsorption/desorption cycles, CaCl₂ 0.05 M eluted nearly 40% of both metals and decreased the biosorption in only 8% and 17% of Cd²⁺ and Zn²⁺, respectively. Although NaOH desorbent improved the heavy metal uptake from the second cycle onwards, it did not elute metals from the pre-loaded biomass.     

Biosorption of chromium to fungi

Eighteen fungal strains were isolated from water and soil samples and tested for their ability to enrich chromium. The microorganism with the highest enrichment capacity, a zygomycete (Mucor hiemalis MP/92/3/4), was chosen for detailed investigations. Some basic tests such as the pH-dependence, the kinetics of the enrichment and the metal selectivity were carried out with the two most frequent oxidation states of chromium, the trivalent cation (Cr³⁺) and the hexavalent anion (CrO₄ ^2–). With Cr³⁺ the enrichment showed a saturation kinetic reaching 70% of the maximum capacity after about 30 min, whereas with CrO₄ ^2– a linear time course with a much lower metal enrichment was observed. The highest level of enrichment for Cr³⁺ was observed at pH 5.5 (21.4 mg/g dry wt), and for CrO₄ ^2– at pH 1 (4.3 mg/g dry wt). Investigations concerning the metal enrichment selectivity resulted in the following series of decreasing ion uptake: Cr³⁺ > Cu²⁺ > Pb²⁺ > Ag⁺ > Al³⁺ > Co²⁺ > Zn²⁺ > Ni²⁺ > Fe²⁺ > Mo⁵⁺ > Cd²⁺ > ^2– > CrO₄ ^2– > VO^3–, calculated on a molar basis. Trivalent chromium caused a staining of the outer cell wall region in transmission electron microscopy. The localization of chromium in the stained outer layers of the cell wall could be verified by electron energy loss spectroscopy. The enrichment of Cr³⁺ by M. hiemalis seemed to be mainly a passive biosorption to the cell wall, whereas for the uptake of CrO₄ ^2– intracellular accumulation as well as biosorption is possible.     

Biosorption of Heavy Metals (Cd2+, Cu2+, Co2+, and Mn2+) by Thermophilic Bacteria,Geobacillus thermantarcticus and Anoxybacillus amylolyticus: Equilibrium and Kinetic Studies

ABSTRACT

Two strains of thermophilic bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus, were employed to investigate the biosorption of heavy metals including Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ ions. The effects of different biosorption parameters such as pH (2.0–10.0), initial metal concentrations (10.0–300.0 mg L^?1), amount of biomass (0.25–10 g L^?1), temperature (30–80°C), and contact time (15–120 min) were investigated. Concentrations of metal ions were determined by using an inductively coupled plasma optical emission spectrometry (ICP-OES). Optimum pHs for Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ biosorption by Geobacillus thermantarcticus were found to be 4.0, 4.0, 5.0, and 6.0, respectively. For Anoxybacillus amylolyticus, the optimum pHs for Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ biosorption were found to be 5.0, 4.0, 5.0, and 6.0, respectively. The Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ removals at 50 mg L^?1 in 60 min by 50 mg dried cells of Geobacillus thermantarcticus were 85.4%, 46.3%, 43.6%, and 65.1%, respectively, whereas 74.1%, 39.8%, 35.1%, and 36.6%, respectively, for Anoxybacillus amylolyticus. The optimum temperatures for heavy metal biosorption were near the optimum growth temperatures for both strains. Scatchard plot analysis was employed to obtain more compact information about the interaction between metal ions and biosorbents. The plot results were further studied to determine if they fit Langmuir and Freundlich models.     

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     

Comparison of Rhizopus nigricans in a pelleted growth form with some other types of waste microbial biomass as biosorbents for metal ions

Biosorption of metal ions (Li⁺, Ag⁺, Pb²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Cu²⁺, Sr²⁺, Fe²⁺, Fe³⁺ and Al³⁺) by Rhizopus nigricans biomass was studied. It was shown that metal uptake is a rapid and pH-dependent process, which ameliorates with increasing initial pH and metal concentrations. Different adsorption models: Langmuir, Freundlich, split-Langmuir and combined nonspecific-Langmuir adsorption isotherm were applied to correlate the equilibrium data. The maximum biosorption capacities for the individual metal ions were in the range from 160 to 460 mol/g dry weight. Scatchard transformation of equilibrium data revealed diverse natures of biomass metal-binding sites. The binding of metals was also discussed in terms of the hard and soft acids and bases principle. The maximum biosorption capacities and the binding constant of R. nigricans were positively correlated with the covalent index of metal ions.The following types of waste microbial biomass originating as by-products from industrial bioprocesses were tested for biosorption of metal ions: Aspergillus terreus, Saccharomyces cerevisiae, Phanerochaete chrysosporium, Micromonospora purpurea, M. inyoensis and Streptomyces clavuligerus. The determined maximum biosorption capacities were in the range from 100 to 500 mol/g dry weight. The biosorption equilibrium was also represented with Langmuir and Freundlich sorption isotherms.     

Biosorptive removal of chromium by husk of Lathyrus sativus: Evaluation of the binding mechanism,kinetic and equilibrium study

The adsorption of tri‐ and hexavalent chromium by the husk of Lathyrus sativus (HLS), which is an agro‐waste has been investigated to find a potential solution to environmental pollution. The pH‐dependent adsorption process finds the optimum values for trivalent and hexavalent chromium ions at about pH 5.0 and pH 2.0, respectively. The process is very fast initially and attains an equilibrium within 90 min following pseudo second‐order rate kinetics. Equilibrium adsorption data can best elucidated by the Langmuir–Freundlich dual model (r² = 0.998) in comparison with other isotherm models examined indicating that both physi‐ and chemisorption are components of the binding mechanism of chromium ions on HLS. The results show that one gram of HLS can adsorb 24.6 mg Cr³⁺ and 44.5 mg Cr⁶⁺. Fourier transform infrared data and functional group modification experiments indicate that –NH₂, ‐COOH, ‐OH, ‐PO₄^3? groups of the biomass interact chemically with the chromium ions. SEM‐energy dispersive X‐ray analysis and X‐ray diffraction spectrum analysis were used to further assess the morphological changes and the mechanisms of chromium ion interaction with HLS. The analysis signified that the biosorption process involved surface morphological changes, complexation and an ion exchange mechanism. The amorphous nature of HLS facilitating metal biosorption was indicated by the X‐ray diffraction analysis.     

Interactive biosorption by microalgal biomass as a tool for fluoride removal

Maximum biosorption of Ca²⁺ was at 50 mg Ca²⁺ l^–1 with both Anabaena fertilissima (2.8 mg Ca²⁺ g^–1 dry wt) and Chlorococcum humicola (4.4 mg g^–1). Such Ca²⁺-treated biomasses, accumulated, respectively, 7 mg F g^–1 DW from an aqueous solution of 10 mg F l^–1 and 4.5 mg F g^–1 DW from 15 mg F l^–1. Data for both Ca²⁺ and F^– biosorption fitted the Langmuir adsorption isotherm indicating monolayer adsorption at a constant energy.     

Biosorption of heavy metal ions by brown seaweeds from southern coast of Korea

Heavy metal ions (Pb²⁺, Cd²⁺, Mn²⁺, Cu²⁺, and Cr₂O₇ ^2?) were biosorbed by brown seaweeds (Hizikia fusiformis, Laminaria japonica, and Undaria pinnatifida) collected from the southern coast of South Korea. The biosorption of heavy metal ions was pH-dependent showing a minimum absorption at pH 2 and a maximum biosorption at pH 4 (Pb²⁺, Cd²⁺, Mn²⁺, and Cr₂O₇ ^2?) or pH 6 (Cu²⁺). Biosorption increased most noticeably for pH changes from 2 to 3. In the latter pH range, biosorption increased, because a higher pH decreased the electrostatic repulsion between metal ions and functional groups on the seaweed. In the pH range of 2 ～ 4, biosorption of negatively-charged chromium species (Cr₂O₇ ^?2) followed the pattern of positively-charged metal ions (Pb²⁺, Cd²⁺, Mn²⁺, and Cu²⁺). This suggests that the most prevalent chromium species were positively-charged Cr³⁺, reduced from Cr⁶⁺ in Cr₂O₇ ^?2. Whereas positively-charged heavy metal ions (Pb²⁺, Cd²⁺, Mn²⁺, and Cu²⁺) reached a plateau after the maximum level, biosorption of chromium ions decreased noticeably between pH 5 and 8. Kinetic data showed that biosorption by brown seaweed occurred rapidly during the first 10 min, and most of the heavy metals were bound to the seaweed within 30 min. Equilibrium adsorption data for a lead ion could fit well in the Langmuir and Freundlich isotherm models with regression coefficients (R ²) between 0.93 and 0.98.     

Structural characteristics of the saxitoxin receptor on nerve

Summary The effects of uranyl ion (UO ₂ ²⁺ ; at low concentrations binds specifically to phosphate groups) and the cationic dye methylene blue (MB⁺; binds strongly to carboxyl groups) on saxitoxin (STX) potency in crayfish axon has been studied by means of intracellular microelectrodes. At pH 6.00±0.05 and 13.5mm Ca²⁺, addition of 10.0 m UO ₂ ²⁺ +5.0nm STX had only slightly, if any, less effect on the spike's maximum rate of rise [0.79±0.04 (viz., mean±sem) of control value] than did addition of 5.0nm STX alone (0.72±0.05). Under the same conditions of pH and Ca²⁺ concentration, 1.0mm MB⁺ had approximately the same effect: 1.0mm MB⁺+5.0nm STX, 0.76±0.03; 5.0nm STX alone, 0.70±0.04. However, at pH 7.00±0.05 and lower Ca²⁺ concentrations, 1.0mm MB⁺ significantly reduced STX potency. Using 6.0mm Ca²⁺: 1.0mm MB⁺+5.0nm STX, 0.92±0.01; 5.0nm STX alone, 0.68±0.08. Using 3.0mm Ca²⁺, the corresponding values were 0.94±0.03 and 0.67±0.04. It is concluded that: (1) In accord with previous suggestions, the ionized acidic group known to exist in the Na channel (and to which a guanidinium group of STX appears to bind) is very likely a carboxyl group and not a phosphate group. (2) The accessible part of the Na channel mouth serving as the saxitoxin receptor probably does not include phospholipid in its structure proper.     

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 with Algae: A Statistical Review

ABSTRACT

The state of the art in the field of biosorption using algae as biomass is reviewed. The available data of maximum sorption uptake (q_max) and biomass-metal affinity (b) for Cd^{2 +}, Cu^{2 +}, Ni^{2 +}, Pb^{2 +} and Zn^{2 +} were statistically analyzed using 37 different algae (20 brown algae, 9 red algae and 8 green algae). Metal biosorption research with algae has used mainly brown algae in pursuit of treatments, which improve its sorption uptake. The information available in connection with multimetallic systems is very poor. Values of q_max were close to 1 mmol/g for copper and lead and smaller for the other metals. Metal recovery performance was worse for nickel and zinc, but the number of samples for zinc was very small. All the metals except lead present a similar affinity for brown algae. The difference in the behavior of lead may be due to a different uptake mechanism. Brown algae stand out as very good biosorbents of heavy metals. The best performer for metal biosorption is lead.     

Biosorption of Copper by Paenibacillus polymyxa Cells and their Exopolysaccharide

Summary Biosorption of heavy metals by gram-positive, non-pathogenic and non-toxicogenic Paenibacillus polymyxa P13 was evaluated. Copper was chosen as a model element because it is a pollutant originated from several industries. An EPS (exopolysaccharide)-producing phenotype exhibited significant Cu(II) biosorption capacity. Under optimal assay conditions (pH 6 and 25 °C), the adsorption isotherm for Cu(II) in aqueous solutions obeyed the Langmuir model. A high q value (biosorption capacity) was observed with whole cells (q_max=112 mgCu g⁻¹). EPS production was associated with hyperosmotic stress by high salt (1 M NaCl), which led to a significant increase in the biosorption capacity of whole cells (q_max=150 mgCu g⁻¹). Biosorption capacity for Cu(II) of the purified EPS was investigated. The maximum biosorption value (q) of 1602 mg g⁻¹ observed with purified EPS at 0.1 mg ml⁻¹ was particularly promising for use in field applications.     

Ion exchange/complexation of the uranyl ion by Rhizopus biosorbent

Nonliving biomass of nine Rhizopus species effectively sequestered the uranyl ion from solution, taking up 150-250 mg U/g dry cells at 300 ppm U equilibrium concentration in solution, and 100-160 mg U/g dry cells with 100 ppm U in solution. The affinity of this biosorbent for the uranyl ion was found to be affected by timing of harvesting and medium composition. Uptake of the uranyl ion by nonliving biomass of Rhizopus oligosporus was due to ion exchange or complexation, since binding was reversed by the addition of complexing ligands or the reduction of pH to a value less than 2. Uptake isotherms were interpreted in terms of a model of multiple equilibria. At pH 相似文献   

Biosorption of tributyltin and other organotin compounds by cyanobacteria and microalgae

Biosorption of triorganotin compounds by the cyanobacteria Synechocystis PCC 6803 and Plectonema boryanum and the microalga Chlorella emersonii, incubated in 2-(N-morpholino)ethanesulphonic acid (MES) buffer, pH 5.5, in the presence of 0.5 mm organotin (supplied as chlorides), increased with molecular mass of the organotins, the order being triphenyltin > tributylin (Bu₃SnCl) > tripropyltin >- trimethyltin >- triethylin. In the butylin series, monobutyltin biosorption was lowest, although levels of dibutyltin uptake were greater than for Bu₃SnCl. Cyanobacterial Bu₃SnCl biosorption was complete in 5 min with no subsequent accumulation. In contrast, a second phase of uptake in C. emersonii resulted in an approximate 2.4-fold increase in cellular Bu₃SnCl between 5 min and 2 h. The external pH had a marked influence on biosorption of Bu₃SnCl by Synechocystis PCC 6803 and P. boryanum, with maximal uptake at pH 5.5 and 6.5, respectively. Effects of pH were less evident in C. emersonii. In all the organisms examined, no inhibition of Bu₃SnCl biosorption was observed between 0.05 and 50 mm NaCl. However, an increase in the external NaCl concentration from 50 to 500 mm resulted in an approximate 55–65% reduction in Bu₃SnCl uptake. Biosorption increased at increasing Bu₃SnCl concentrations (0.25–3.0 mm). Saturation of Bu₃SnCl biosorption at the higher concentrations was most evident in the cyanobacteria, although uptake levels were greater in these organisms at <- 2 mm Bu₃SnCl. Theoretical maximum biosorption levels at complete cell saturation, derived from reciprocal Langmuir plots, were approximately 565, 525 and 1050 nmol Bu₃SnCl mg^–1 dry weight, for Synechocystis PCC 6803, P. boryanum and C. emersonii, respectively. Correspondence to: G. M. Gadd     

Sorption of heavy metals by four basidiomycetous fungi

Biosorptions of Pb²⁺, Cr⁶⁺, Cd²⁺ and Ni²⁺ were investigated, with special emphasis on the first one, using live and dead fungal mycelia. Of the four fungi, namely Polyporus ostreiformis, Volvariella volvacea, Pleurotus sajor-caju and Phanerochaete chrysosporium, the last one was found to be most effective in Pb²⁺ removal. Total biosorption was effected in 6 days up to the Pb²⁺ concentration of 6 mg/l, with a specific uptake of 1.33 mg Pb²⁺/g dry cell mass. The removal of other three metals varied between 28.8–73.3% from a medium containing 4 mg/l of each of the metals.Laboratory facilities created under M.Tech programme in Biotechnology and Engineering (sponsored by Department of Biotechnology, Govt. of India) were partly utilized for this study.