Biosorption of Cu(II) and Pb(II) ions from aqueous solution by natural spider silk

Aside from its excellent mechanical properties, spider silk (SS) would offer an active surface for heavy metal interaction due to its rich protein structure. The present study describes the potential use of natural (SS) as a sorbent of heavy metals from aqueous solutions. Single and multi-species biosorption experiments of heavy metals by natural SS were conducted using batch and column experiments. The biosorption kinetics, in general, was found to follow the second-order rate expression, and the experimental equilibrium biosorption data fitted reasonably well to Freundlich isotherm. From the Freundlich isotherm, the biosorption capacities of Cu(II) and Pb(II) ions onto SS were found as 0.20 and 0.007 mmol g?1, respectively. The results showed a decrease in the extent of metal ion uptake with lowering the pH.     

Biosorption of lead and nickel by living and non-living cells of Pseudomonas aeruginosa ASU 6a

The optimum conditions for biosorption and bioaccumulation of lead and nickel were investigated by using a tolerant bacterial strain isolated from El-Malah canal, Assiut, Egypt, and identified as Pseudomonas aeruginosa ASU 6a. The experimental adsorption data were fitted towards the models postulated by Langmuir and Freundlich isotherm equations. The binding capacity by living cells is significantly lower than that of dead cells. The maximum biosorption capacities for lead and nickel obtained by using non-living cells and living cells were 123, 113.6 and 79, 70 mg/g, respectively. The biosorptive mechanism was confirmed by IR analysis and from the identification nature of acidic and basic sites. Moreover, the postulated mechanism was found to depend mainly on ionic interaction and complex formation.     

Biosorption of cadmium by a Cd2+-hyperresistant Bacillus cereus strain HQ-1 newly isolated from a lead and zinc mine

A Cd²⁺-hyperresistant bacterial strain HQ-1 was isolated from a lead–zinc mine. The strain was characterized and identified as Bacillus cereus based on morphology, physiological tests and 16S rRNA gene analysis. The minimal inhibitory concentration of Cd²⁺ for the bacterium was 0.012 mol/l. Isotherms for cadmium (Cd) biosorption by cells of B. cereus strain HQ-1 were investigated. The equilibrium data could be fitted by a Langmuir isotherm equation. The possible functional sites that might be influenced by the sorption were determined. The results indicate that this B. cereus strain has excellent potential for biosorption of Cd. Physiological characterization of the isolate also indicates possible application of this strain for bioremediation of sites with Cd contamination.     

Biosorption of acid violet dye from aqueous solutions using native biomass of a new isolate of Penicillium sp.

Laboratory investigation of the potential use of Penicillium sp. as biosorbent for the removal of acid violet dye from aqueous solution was studied with respect to pH, temperature, biosorbent, initial dye concentrations. Penicillium sp. decolourizes acid violet (30 mg l⁻¹) within 12 h agitation of 150 rpm at pH 5.7 and temperature of 35 °C. The pellets exhibited a high dye adsorption capacity (5.88 mg g⁻¹) for acid violet dye over a pH range (4–9); the maximum adsorption was obtained at pH 5.7. The increase of temperature favored biosorption for acid violet, but the optimum temperature was 35 °C. Adsorption kinetic data were tested using pseudo-first-order, pseudo-second-order and kinetic studies showed that the biosorption process follows pseudo-first-order rate kinetics with an average rate constant of 0.312 min⁻¹. Isotherm experiments were conducted to determine the sorbent–desorption behavior of examined dye from aqueous solutions using Langmuir and Freundlich equations. Langmuir parameter indicated a maximum adsorption capacity of 4.32 mg g⁻¹ for acid violet and R_L value of 0.377. Linear plot of log q_e vs log C_e shows that applicability of Freundlich adsorption isotherm model. These results suggest that this fungus can be used in biotreatment process as biosorbent for acid dyes.     

Cloning,functional expression and expression studies of the nitrate transporter gene from Chlorella sorokiniana (strain 211-8k)

The nitrate transporter from Chlorella sorokiniana (accession number AY026523) has been cloned by screening a cDNA library based on mRNA isolated after 30 min treatment of Chlorella with 5 mM nitrate and with a RT-PCR product (730 bp) as a probe. The Chlorella sequence has similarity to known nitrate transporters of the NRT2 family (high-affinity nitrate transporters). The cDNA clone was used for functional expression in Xenopus oocytes and a nitrate-dependent current was measured at pH 5.5 but not at pH 7.4. A second algal gene or a second gene product was not needed for functional expression in Xenopus. Inhibitor studies in Chlorella indicated that protein phosphorylation/dephosphorylation is involved in nitrate induction of ChNRT2.1. In addition to nitrate, ChNRT2.1 expression is induced by nitroprusside, a NO donor, and is affected by glucose.     

Removal of inorganic ions from wastewaters by immobilized microalgae

Anabaena doliolum and Chlorella vulgaris immobilized on chitosan were more efficient at removing NO₃ ^–, NO₂ ^p–, PO₄ ^3– and CR₂O₇ ^2– from wastewaters than cells immobilized on agar, alginate, carrageenan or even free cells. Carrageenan-immobilized cells, however, were better at removing NH₄ ⁺ and Ni²⁺. The PO₄ ^3– uptake capacity was significantly increased in cells starved of PO₄ ^3– for 24 h. Agar-immobilized cells, though having good metal and nutrient uptake efficiency, had only a slow growth rate. Chitosan is recommended as an algal support for wastewater detoxification.The authors are with the Laboratory of Algal Biology, Department of Botany, Banaras Hindu University, Varanasi-221005, India     

Biosorption of thorium (IV) by a Pseudomonas biomass

Lyophilized biomass of a Pseudomonas soilisolate adsorbed thorium (IV) (430 mg g^–1 dry wt) optimally at pH 4, with 91% of equilibrium loading being reached in 1 min. Equilibrium metal sorption showing conformity to Langmuir isotherm model suggested a monolayered thorium binding. Thorium binding remained unaffected or slightly affected (< 20% inhibition) in presence of equimolar (430 M) concentration of several interfering ions except Fe³⁺ (40% inhibition). More than 90% of loaded thorium could be recovered using 1 M CaCO₃, though mineral acids and Na₂CO₃ were also effective.     

Removal and assessment of toxicity of Cu and Fe toAnabaena doliolum andChlorella vulgaris using free and immobilized cells

Alginate-immobilized and free cells ofAnabaena doliolum andChlorella vulgaris were compared for their use in the removal and toxicity bioassays of Cu and Fe. A decrease in toxicity with regard to growth and uptake of NO ₃ ^– and NH ₄ ⁺ was noticed following immobilization of both the organisms. In contrast, immobilized cells had higher uptake rates of Cu and Fe suggesting that immobilization offers protection against metal toxicity. Compared with free cells, the immobilized cells showed greater efficiency for metal removal, even over three repeated cycles, though with a gradual decrease in efficiency in the second and third cycles. This reduction in removal efficiency was, however, more pronounced for Fe withA. doliolum and for Cu withC. vulgaris. The ease in harvesting and potential for repeated use makes the immobilized cells good tools for scavenging heavy metals from metal-contaminated environments.     

Isolation and characterization of brassinosteroids from algal cultures of Chlorella vulgaris Beijerinck (Trebouxiophyceae)

The brassinosteroids (BRs) occur ubiquitously in the plant kingdom. The occurrence of BRs has been demonstrated in almost every part of higher plants, such as pollen, flower buds, fruits, seeds, vascular cambium, leaves, shoots and roots. In this study, BRs were isolated and identified in the culture of wild-type Chlorella vulgaris. Seven BRs, including teasterone, typhasterol, 6-deoxoteasterone, 6-deoxotyphasterol, 6-deoxocastasterone, castasterone and brassinolide, were identified by GC–MS. All compounds belong to the BR biosynthetic pathway. The results suggest that early and late C6 oxidation pathways are operating in C. vulgaris. This study represents the first isolation of BRs from C. vulgaris cultures.     

A new synthetic species of Cucumis (Cucurbitaceae) from interspecific hybridization and chromosome doubling

A new synthetic species,Cucumis hytivus J.-F. Chen & J. H. Kirkbr. (2n=38), obtained by doubling the number of chromosomes in the sterile interspecific F₁ hybrid (2n=19) betweenC. sativus L. (2n=14) andC. hystrix Chakr. (2n=24), is described.     

Biosorption of Cr(VI) onto marine Aspergillus niger: experimental studies and pseudo-second order kinetics

The removal of hexavalent chromium from aqueous solution was studied in batch experiments using dead biomass of three different species of marine Aspergillus after alkali treatment. All the cultures exhibited potential to remove Cr(VI), out of which, Aspergillus niger was found to be the most promising one. This culture was further studied employing variation in pH, temperature, metal ion concentration and biomass concentration with a view to understand the effect of these parameters on biosorption of Cr(VI). Higher biosorption percentage was evidenced at lower initial concentration of Cr(VI) ion, while the sorption capacity of the biomass increased with rising concentration of ions. Biomass as low as 0.8 g l⁻¹ could biosorb 95% Cr(VI) ions within 2,880 min from an aqueous solution of 400 mg l⁻¹ Cr(VI) concentration. Optimum pH and temperature for Cr(VI) biosorption were 2.0 and 50°C, respectively. Kinetic studies based on pseudo second order models like Sobkowsk and Czerwinski, Ritchie, Blanchard and Ho and Mckay rate expressions have also been carried out. The nature of the possible cell–metal ion interactions was evaluated by FTIR, SEM and EDAX analysis.     

Synthesis and characterization of a crosslinked chitosan derivative with a complexing agent and its adsorption studies toward metal(II) ions

A new chitosan derivative has been synthesized by crosslinking a metal complexing agent, [6,6′-piperazine-1,4-diyldimethylenebis (4-methyl-2-formyl) phenol] (L), with chitosan (CTS). The resulting material (CCTSL) was characterized by elemental (CHN), spectral (FTIR and solid-state NMR), thermal (TGA and DTA), and structural (powder XRD and SEM) analyses. Adsorption experiments (pH dependency, kinetics, and equilibrium) of CCTSL toward various metal ions such as Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II) were carried out at 25 °C. The results showed that the adsorption was dependent on the pH of the solution, with a maximum capacity between pHs 6.5 and 8.5. The kinetics was evaluated by applying the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The maximum adsorption capacity was 1.21 mmol g⁻¹ for Cu(II) and the order of adsorption capacities for the metal(II) ions studied was found to be Cu(II) > Ni(II) > Cd(II)  Co(II)  Mn(II)  Fe(II)  Pb(II).     

Bioaccumulation and biosorption efficacy of Trichoderma isolate SP2F1 in removing copper (Cu(II)) from aqueous solutions

In our study, we isolated the isolate Trichoderma SP2F1 from sediment samples from the Penchala River, heavily contaminated with effluents from nearby industrial areas. Qualitative and quantitative screening using plate and broth assay, respectively, supplemented with various concentrations of Cu(II) showed the isolate was able to tolerate 6 mM CuSO₄, although growth was also detected in broths with 10 mM CuSO₄. Trichoderma spp. was able to remove Cu(II) in aqueous solutions in both viable and non-viable cell forms. Bioaccumulation capacity of viable SP2F1 cells removed 19.60 mg g⁻¹ of Cu(II) after 168 h incubation, while the maximum Cu(II) biosorption capacity for non-viable SP2F1 cells was 28.75 mg g⁻¹ of Cu(II). Results here showed that Trichoderma spp isolate SP2F1 has good potential for application in Cu(II) removal, can be used to treat sewage waste by applying either in viable or non-viable cell forms.     

Biosorption of manganese by <Emphasis Type="Italic">Aspergillus niger</Emphasis> and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Summary Biosorption of manganese from its aqueous solution using yeast biomass Saccharomyces cerevisiae and fungal biomass Aspergillus niger was carried out. Manganese biosorption equilibration time for A. niger and S. cerevisiae were found to be 60 and 20 min, with uptakes of 19.34 and 18.95 mg/g, respectively. Biosorption increased with rise in pH, biomass, and manganese concentration. The biosorption equilibrium data fitted with the Freundlich isotherm model revealed that A. niger was a better biosorbent of manganese than S. cerevisiae.     

A new species of Eumonhystera and three species of Monhystera (Monhysteridae: Nematoda) from Li River,China

A new Eumonhystera species, E. huruii n. sp., together with Monhystera nubiae Eyualem & Coomans, 1996, Monhystera somereni Allgén, 1952, and Monhystera wangi Wu & Hoeppli, 1932 are described from Li river at Guiling, China. Eumonhystera huruii n. sp. is closest to E. barbata Andrássy, 1981, but differs in having shorter anterior setae, much longer reproductive system, shorter and less dorsally bent tail and differently shaped spinneret. M. nubiae and M. wangi are reported here for the first time outside their type locality, whereas M. somereni is reported from China for the first time.     

Adsorption of lead(II) from aqueous solution onto Hydrilla verticillata

The adsorption of Pb(II) onto Hydrilla verticillata was examined in aqueous solution with parameters of pH, adsorbent dosage, contact time and temperature. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) was found as 104.2 mg/g at pH 4 and 25°C. Dubinin–Radushkevich (D–R) isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (15.81 kJ/mol) indicated that the adsorption of Pb(II) onto H. verticillata may be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, free energy (ΔG ⁰), enthalpy (ΔH ⁰) and entropy (ΔS ⁰) of adsorption were also calculated. These parameters showed that the adsorption of Pb(II) onto H. verticillata was a feasible, spontaneous and exothermic process in nature. The influence of Cd²⁺, Cu²⁺ and Ni²⁺ on adsorption of Pb²⁺ onto H. verticillata was studied, too. In the investigated range of operating conditions, it was found that the existence of Cd ²⁺, Cu ²⁺ and Ni ²⁺ had no impact on the adsorption of Pb²⁺.     

Observations on three species of branchiobdellid (Annelida: Clitellata) worms from eastern Asia

Three jars from the Hamburg Museum contained specimens of Branchiobdella minuta, presumably from the original Pierantoni (1912) material, and Cirrodrilus cirratus and C. uchidai from Yamaguchi's (1932a) collection. The head of a syntype of B. minuta was described and B. cheni becomes its junior subjective synonym. One specimen each of C. cirratus and C. uchidai was sectioned and described, particularly the male genitalia. The diet of all three branchiobdellids consists of microorganisms. In Cirrodrilus sp. basic protein granules were demonstrated in the gland cells of the intestine and its chloragogen cells. The peristomial and lateral epidermal gland cell secretions were characterized histochemically.     

Bambusicolous fungi in Japan (5): three species of Tetraploa

Three species of Tetraploa collected from Sasa, or bamboos, are described and illustrated. Among them, T. curviappendiculata on Sasa kurilensis and T. longissima on Pleioblastus chino are compared with hitherto known species and described as new species. In the nomenclature, T. javanica is substituted for T. biformis, formerly reported from the dead bark of a broad-leaved tree in Japan, as a correct name.