Comparative studies on metal biosorption by two strains of Cladosporium cladosporioides

Two strains of a fungus, Cladosporium cladosporioides 1 and C. cladosporioides 2 showed different metal biosorption properties. Strain 1 showed preferential sorption of gold and silver, while strain 2 could bind metals such as copper and cadmium in addition to gold and silver. Strain 1 had a cell-wall hexosamine content of 0.1%. X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR) analyses indicated that nitrogen was not involved in metal biosorption by the strain. In strain 2 the cell-wall hexosamine content was 150 times that of strain 1. These results indicated that hexosamine was responsible for non-specific metal binding while cell-wall polymers other than hexosamines had a role in conferring selectivity in precious-metal binding.     

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.     

A method to increase silver biosorption by an industrial strain of Saccharomyces cerevisiae

 Ag⁺ biosorption by an industrial strain of Saccharomyces cerevisiae was investigated. Older (96 h old) biomass had half the biosorption capacity of younger (24 h old) biomass (0.187 and 0.387 mmol Ag⁺/g dry mass respectively). Comparisons of cell walls isolated from biomass of either age indicated that chemical composition and Ag⁺ biosorption capacity varied little over the time span examined and that cell walls from either age of culture had small Ag⁺ biosorption capacities compared to whole cells of a similar age. Silver-containing precipitates were observed both on the cell wall and within the cell, indicating that intracellular components sorbed Ag⁺. The concentration of these precipitates within the cell appeared visually to decrease with age in Ag⁺-exposed cells. Incorporation of L-cysteine into the growth medium resulted in biomass with increased silver biosorption capacities, protein and sulphydryl group content. Increasing the concentration of L-cysteine in the growth medium from 0 to 5.0 mM increased silver biosorption from 0.389 to 0.556 mmol Ag⁺/g dry mass Isolated cell walls of biomass grown in supplemented media also showed a possible link between silver biosorption capacities, protein and sulphydryl group content. No precipitates were observed in silver-exposed biomass that had been grown in the presence of 5.0 mM L-cysteine. Received: 12 April 1995 / Received revision: 7 August 1995 / Accepted: 22 August 1995     

Cu2+ Removal and recovery by Spi SORB: batch stirred and up-flow packed bed columnar reactor systems

The biosorption of Cu²⁺ by free and poly acrylamide gel (PAG) immobilized Spirulina platensis (SpiSORB) was characterized under batch and continuous packed bed columnar reaction systems. The biosorption of Cu²⁺ was shown to be highest at pH of 6.0 for both types of biomass. The PAG immobilization process did not interfere with the Cu²⁺ binding sites present on biomass leading to cent percent (ca. 250 mg g⁻¹ of dry biomass) retention of biosorption as compared to free cells. Transmission electron microscopy on Cu²⁺ localization revealed that majority of metal is being sequestered by the cell wall only. The infrared spectrum of metal treated S. platensis biomass indicated the possible involvement of amide, amino, and carboxyl groups in metal binding. Up-flow packed bed columnar reactor containing 2.0 g of PAG immobilized S. platensis shown a maximum of 143-fold volume reduction factor at the residence time of 4.6 min for Cu²⁺ alone and found to decrease dramatically when Zn²⁺ is present in a bimetallic solution.     

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.     

Studies on metal resistance system inKluyveromyces marxianus

Through preliminary plate tests,Kluyveromyces marxianus was found to be much more resistant to toxic heavy metals compared to aCUP1 ^R strain ofSaccharomyces cerevisiae. Specific growth rate and maximum dry weights affected by increasing metal concentrations were determined to obtain precise patterns of resistance. Metal biosorption was also monitored during the course of growth in synthetic media containing respective metals at 0.5 mM final concentration. Although Zn- and Co-binding was negligible, as much as 90% of silver, 60% of copper, and 65% of cadmium were found to be absorbed by the end of active growth. Analysis of the protein profiles ofS. cerevisiae andK. marxianus on metal exposure suggested constitutive production of metallothionein inK. marxianus. Furthermore, a smaller protein synthesized byK. marxianus on induction by silver or cadmium accounts for the high resistance of the organism to these metals.     

Biosorption behavior of heavy metals in bioleaching process of MSWI fly ash by Aspergillus niger

In this study, it was considered that the biosorption of heavy metals by biomass might occur during the bioleaching of fly ash. This work is focused on the biosorption behavior of Al, Fe, Pb and Zn by Aspergillus niger during the bioleaching process. The fungal biomass was contacted with heavy metals solution which extracted from fly ash by using gluconic acid as leaching agent. The equilibrium time for biosorption was about 120 min. The biosorption experiment data at initial pH 6.5 was used to fit the biosorption kinetics and isotherm models. The results indicated that the biosorption of Al, Fe and Zn by A. niger biomass were well described by the pseudo-first order kinetic model. The pseudo-second order kinetic model was more suitable for that of Pb. The Langmuir isotherm model could well describe the biosorption of Fe, Pb and Zn while the Freundlich model could well describe the biosorption of Al. Furthermore, the biosorption of metal ions decreased evidently in the presence of fly ash as compared to that in the absence of fly ash. This research showed that although the biomass sorption occurred during the bioleaching process, it did not inhibit the removal of Al, Fe, Pb and Zn evidently from fly ash.     

Immobilization of blue green microalgae on loofa sponge to biosorb cadmium in repeated shake flask batch and continuous flow fixed bed column reactor system

Summary An indigenous strain of blue green microalga, Synechococcus sp., isolated from wastewater, was immobilized onto loofa sponge discs and investigated as a potential biosorbent for the removal of cadmium from aqueous solutions. Immobilization has enhanced the sorption of cadmium and an increase of biosorption (21%) at equilibrium was noted as compared to free biomass. The kinetics of cadmium biosorption was extremely rapid, with (96%) of adsorption within the first 5 min and equilibrium reached at 15 min. Increasing initial pH or initial cadmium concentration resulted in an increase in cadmium uptake. The maximum biosorption capacity of free and loofa immobilized biomass of Synechococcus sp. was found to be 47.73 and 57.76 mg g⁻¹ biomass respectively. The biosorption equilibrium was well described by Langmuir adsorption isotherm model. The biosorbed cadmium was desorbed by washing the immobilized biomass with dilute HCl (0.1 M) and desorbed biomass was reused in five biosorption–desorption cycles without an apparent decrease in its metal biosorption capacity. The metal removing capacity of loofa immobilized biomass was also tested in a continuous flow fixed-bed column bioreactor and was found to be highly effective in removing cadmium from aqueous solution. The results suggested that the loofa sponge-immobilized biomass of Synechococcus sp. could be used as a biosorbent for an efficient removal of heavy metal ions from aqueous solution.     

Studies on Uranium Removal by the Extracellular Polysaccharide of a Pseudomonas aeruginosa Strain

Extracellular polysaccharide (EPS) produced by a Pseudomonas aeruginosa strain BU2 was characterized for its ability to remove uranium from aqueous solution. The EPS was acidic in nature and found as a potent biosorbent for uranium (U), showing pH dependence and fast saturating metal sorption, being maximum (985 mg U g^{? 1} EPS) at pH 5.0. The polymer showed enhanced uranium sorption capacity and affinity with increasing solution pH, suggesting a preferential sorption of monovalent uranyl hydroxide ions over the nonhydroxylated divalent species. Pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental data, assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled. Equilibrium metal binding showing conformity to the Freundlich model suggested a multilayer sorption involving specific binding sites with affinity distribution. The presence of two types of metal binding sites corresponding to strong and weak binding affinity was interpreted from the Scatchard model equation. Uranium sorption by EPS was unaffected or only slightly affected in the presence of several interfering cations and anions, except iron and thorium. Fourier transform infrared (FTIR) spectroscopy ascertained the strong binding of uranium with the carboxylic groups of uronic acids of bacterial EPS at pH 5.0, whereas at lower pH, amino and hydroxyl groups played a major role in metal binding.     

The posibility of soil micromycetes produced the abscisic acid

The typical soil micromycetes Aspergillus niger and Cladosporium cladosporioides from the family moniliaceae were investigated with emphasis on production of ABA into the culture medium. The both fungi were cultivated in a static liquid Czapek — Dox medium and agar Czapek — Dox medium. Aspergillus niger and Cladosporium cladosporioides showed ability to produce ABA. Analytical detection of ABA from the culture medium was performed by TLC combinated with biotest and HPLC with spectroscopy.     

Biotechnological potential of Microcystis sp. in Cu, Zn and Cd biosorption from single and multimetallic systems

This paper provides information on biosorption of Cu, Zn and Cd by Microcystis sp. in single, bi and trimetallic combination. Highest biosorption of Cu followed by Zn and Cd in single as well as in mixtures containing two or three metals was noticed. The order of inhibition of Cu, Zn and Cd biosorption in bi and trimetallic combinations was suggestive of screening or competition for the binding sites on the cell surface. This observation was reconfirmed by Freundlich adsorption isotherm. K_f values were maximum for Cu (K_f=45.18), followed by Zn (K_f=16.71), and Cd (K_f=15.63) in single metallic system. The K_f values for each test metal was reduced in solution containing more than one metal. Further, the reduction in biosorption of each metal ion due to presence of other metal ion was of greater magnitude at relatively higher concentrations of interfering metal ion. The biosorption of Cu at saturation was less affected when secondary metal (Cd or Zn) was added in the medium. Above results suggest that Microcystis holds great potential for metal biosorption from mixture.     

The mechanism of uranium biosorption by Rhizopus arrhizus

Biosorption of elements is a little understood phenomenon exhibited by some types of even nonliving microbial biomass. A common fungus Rhizopus arrhizus has been reported to take up uranium from aqueous solutions to the extent of 180 mg U(6+)/g. The mechanism of uranium sequestering by this type of biomass was studied by using experimental techniques such as electron microscopy, x-ray energy dispersion analysis, IR spectroscopy, and supporting evidence was obtained for a biosorption mechanism consisting of at least three processes. Uranium coordination and adsorption in the cell-wall chitin structure occur simultaneously and rapidly whereas precipitation of uranylhydroxide within the chitin microcrystalline cell-wall structure takes place at a lower rate. Interference of Fe(2+) and Zn(2+) coions with uranium biosorption is indicated.     

Characterization of Desulfomicrobium escambium sp. nov. and proposal to assign Desulfovibrio desulfuricans strain Norway 4 to the genus Desulfomicrobium

A sulfate-reducing bacterium, designated strain ESC1, was isolated and found to be a new species. Strain ESC1 is a strictly anaerobic, gram-negative, non-sporeforming, motile, short, round-ended rod often occurring in pairs. Of 31 fermentative substrates tested, only pyruvate was utilized. Sulfate enhanced growth with pyruvate and allowed growth with ethanol, lactate, formate and hydrogen. Both sulfate and thiosulfate were reduced. Lactate was incompletely oxidized to acetate and CO₂. The strain was desulfoviridin negative. The G+C content is 59.9%. These data suggested placement of strain ESC1 in the genus Desulfomicrobium. Comparative 16S rRNA analysis showed that strain ESC1 shares 98% rRNA sequence similarity with Desulfomicrobium baculatum and Desulfovibrio desulfuricans strain Norway 4. The latter two strains shared greater than 99% 16S rRNA sequence similarity. Strain ESC1 has been designated as the new species Desulfomicrobium escambium. We also recommend that D. desulfuricans strain Norway 4 be considered for reclassification as a Desulfomicrobium species.     

马利亚霉菌(Mariannaeasp.) HJ合成金属硒化物及机理研究

[背景] 金属硒化物因其优异的光电和催化特性,近年来在半导体、电化学及抗癌等领域成为了研究热点。相较于传统的化学还原法,生物合成金属硒化物具有环境友好、耗能较低等优势。然而,目前有关生物合成金属硒化合物的微生物资源较少且相关合成机理尚不明晰。[目的] 利用马利亚霉菌（Mariannaea sp.） HJ合成了3种金属硒化物并对其合成机理进行了初步探索。[方法] 利用X射线衍射（X-Ray Diffraction,XRD）和傅里叶转换红外线光谱（Fourier Transform Infrared Spectroscopy,FTIR）对菌株HJ合成的金属硒化物进行了初步的表征,考察了纳米材料合成过程中总巯基含量、总抗氧化性能及自由基含量变化,并且验证了转运蛋白DMT1在金属硒化物合成中所起的关键性作用。[结果] XRD结果表明菌株HJ能够在Bi³⁺、Pb²⁺、Co²⁺与SeO₃^2-作用下分别合成Bi₄Se₃、PbSe和CoSe₂纳米颗粒,其合成的最优pH条件分别为6.0、7.0、8.0。FTIR结果表明,合成的金属硒化物表面含有氨基、羧基、羟基等官能团。3种金属硒化物的合成反应体系与空白对照组相比,总巯基含量明显下降,而总抗氧化性能却有所提高,这表明巯基等酶促体系或氨基酸金属蛋白类的非酶促体系可能参与了SeO₃^2-的还原过程。苄基异硫脲盐酸盐屏蔽实验表明,转运蛋白DMT1在SeO₃^2-转运和金属硒化物分泌过程中起到关键作用。此外,Bi³⁺、Pb²⁺和Co²⁺的加入使得菌株HJ产生氧化应激反应,在胞外分泌了大量的过氧化氢、羟基自由基和超氧自由基,而上述自由基可通过诱导热激效应的方式增强金属离子或纳米颗粒的转运过程。[结论] 利用马利亚霉菌（Mariannaeasp.） HJ合成了Bi₄Se₃、PbSe和CoSe₂纳米颗粒,为研究金属硒化物的生物合成及机理提供了一定的理论参考。     

Considerations on the use of commercially available yeast biomass for the treatment of metal-containing effluents

Summary Three strains ofSaccharomyces cerevisiae and one strain of aCandida sp. obtained from different industrial sources were screened for uptake of silver and copper. Considerable differences in metal uptake capacities were found between the different strains ofS. cerevisiae and betweenS. cerevisiae and theCandida sp. used. Copper uptake capacities ranged from 0.05 mmol g^–1 dry wt to 0.184 mmol g^–1 dry wt while values of 0.034 mmol Ag g^–1 dry wt and 0.193 mmol Ag g^–1 dry wt biomass were observed. Use of ion-selective electrodes (ISEs) enabled the detection of copper complexing agents (possibly proteins and carbohydrates) released by yeasts into the surrounding medium. In contrast, these compounds had no silver complexation abilities. Langmuir and Scatchard transformations of metal adsorption isotherms suggested differences in the mechanisms involved in metal uptake by the various yeasts. The differences between strains ofS. cerevisiae were due possibly to differences in cell wal composition. Different methods of preparation of biomass (fresh, air, oven and freeze-dried) had little effect on metal uptake in comparison with fresh biomass. Storage of fresh waste biomass at 4°C for 20 days had no effect on metal biosorption capacities. It was also observed that individual batches of waste biomass produced from different fermentation runs had consistent metal uptake capacities. The implications of the above results on the use of waste yeast biomass for treatment of metal-containing effluents are discussed.     

一株链霉菌21-1的分离鉴定及其对禾谷镰刀菌的抑菌活性

【背景】由禾谷镰刀菌(Fusarium graminearum)引起的小麦赤霉病严重威胁我国的小麦生产。【目的】筛选对禾谷镰刀菌具有拮抗能力的链霉菌菌株,为生防菌剂开发提供理论基础。【方法】利用平板对峙法筛选对禾谷镰刀菌具有拮抗能力的链霉菌;通过形态特征、生理生化特征和16S rRNA基因序列分析对其进行鉴定;通过病原菌菌丝生长、孢子产生及萌发抑制试验分析其发酵液的抑菌活性;利用人工接种试验测定该菌株发酵液的防病效果。【结果】筛选到一株对禾谷镰刀菌具有较强拮抗活性的链霉菌21-1,抑菌率为59.5%。依据形态特征、生理生化特性和16S rRNA基因序列分析,将该菌株鉴定为黄三素链霉菌(Streptomycesflavotricini)。菌株21-1发酵液能够抑制禾谷镰刀菌的菌丝生长、孢子产生及萌发过程,而且可以降低禾谷镰刀菌菌丝中可溶性蛋白质的含量,并增加丙二醛的含量。菌株21-1可以产生蛋白酶及纤维素酶。菌株21-1菌液10倍稀释液对小麦赤霉病的防效最佳,为70.1%。此外,菌株21-1发酵液对其他8种植物病原菌均有较好的抑制作用。【结论】菌株21-1对禾谷镰刀菌有较好的抑菌活性,具...     

假单胞菌T1-3-2的抑菌特性及其对杉木的抗病促生作用

【背景】生物防治是“基于自然的解决方案”,有利于生态文明和可持续发展,开展生物防治技术研究的基础是明确菌株的生防作用和抑菌特性。【目的】探究杉木内生菌株T1-3-2的抑菌促生特性,为研制该菌株生防菌剂、防治杉木炭疽病(Cunninghamia lanceolata anthracnose)奠定基础。【方法】通过形态学特征、生理生化特性及16S rRNA基因序列分析,确定菌株T1-3-2的分类地位;通过平板对峙、菌落径向生长抑制率和平板倒扣等方法测定细菌及其挥发性气体和次级代谢产物的抑菌作用;同时,测定其促生作用和室内防效。【结果】菌株T1-3-2与桉生假单胞菌(Pseudomonas eucalypticola)亲缘性较近,属于假单胞菌属。该菌株对分属于6个属的10株靶标菌株具有较强的拮抗作用,尤其对炭疽菌属、拟盘多毛孢属、黑孢霉属和葡萄座腔菌属的6株靶标菌株抑制率高达80%以上。室内盆栽试验显示：菌株T1-3-2用Kings Medium B液体培养基的发酵菌液对杉木炭疽病的防效可达74.20%,同时能有效改善杉木幼苗的生长状况、增加生物量。【结论】菌株T1-3-2隶属于假单胞菌属,对杉木具有良好的抗病促生作用,是一株具有开发潜力的生防菌株。     

Acetate-mediated pH-stat fed-batch cultivation of transconjugant <Emphasis Type="Italic">Enterobacter</Emphasis> sp. BL-2S over-expressing <Emphasis Type="Italic">glmS</Emphasis> gene for excretive production of microbial polyglucosamine PGB-1

A unique cationic polyglucosamine biopolymer PGB-1 comprising more than 95% D-glucosamine was excretively produced from a new bacterial strain Enterobacter sp. BL-2 under acetate-mediated culture conditions. Since the biopolymer PGB-1 could be synthesized from the UDP-N-acetylglucosamine monomer derived from the hexosamine pathway, three glmS, glmM, and glmU genes in the hexosamine pathway were cloned from Enterobacter sp. BL-2, and their molecular structures were elucidated. The cloned glmS, glmM, and glmU genes were reintroduced into the parent strain Enterobacter sp. BL-2 through a conjugative transformation for the overproduction of the biopolymer PGB-1. The biopolymer production increased 1.5-fold in the transconjugant Enterobacter sp. BL-2S over-expressing the first-step glmS gene encoding glucosamine-6-phosphate synthase. The transconjugant Enterobacter sp. BL-2S was cultivated pH-stat fed-batch widely, while intermittently feeding an acetate solution to maintain a constant pH level of 8.0 for 72 h, resulting in 1.15 g/L of the extracellular polyglucosamine biopolymer PGB-1.     

Biosorption of heavy metals by Bacillus thuringiensis strain OSM29 originating from industrial effluent contaminated north Indian soil

The study was navigated to examine the metal biosorbing ability of bacterial strain OSM29 recovered from rhizosphere of cauliflower grown in soil irrigated consistently with industrial effluents. The metal tolerant bacterial strain OSM29 was identified as Bacillus thuringiensis following 16S rRNA gene sequence analysis. In the presence of the varying concentrations (25–150 mgl⁻¹) of heavy metals, such as cadmium, chromium, copper, lead and nickel, the B. thuringiensis strain OSM29 showed an obvious metal removing potential. The effect of certain physico-chemical factors such as pH, initial metal concentration, and contact time on biosorption was also assessed. The optimum pH for nickel and chromium removal was 7, while for cadmium, copper and lead, it was 6. The optimal contact time was 30 min. for each metal at 32 ± 2 °C by strain OSM29. The biosorption capacity of the strain OSM29 for the metallic ions was highest for Ni (94%) which was followed by Cu (91.8%), while the lowest sorption by bacterial biomass was recorded for Cd (87%) at 25 mgl⁻¹ initial metal ion concentration. The regression coefficients obtained for heavy metals from the Freundlich and Langmuir models were significant. The surface chemical functional groups of B. thuringiensis biomass identified by Fourier transform infrared (FTIR) were amino, carboxyl, hydroxyl, and carbonyl groups, which may be involved in the biosorption of heavy metals. The biosorption ability of B. thuringiensis OSM29 varied with metals and was pH and metal concentration dependent. The biosorption of each metal was fairly rapid which could be an advantage for large scale treatment of contaminated sites.     

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.