Kolishka Tsekova

Biosorption of copper(II) and cadmium(II) from aqueous solutions by free and immobilized biomass of Aspergillus niger

This study investigates the ability of Aspergillus niger resting cells entrapped into poly(vinyl alcohol) (PVA) network to remove Cu(II) and Cd(II) from single ions solutions. The performance of free and immobilized biosorbent was evaluated by equilibrium and kinetic studies. The PVA-immobilized fungal biosorbent removed Cu(II) and Cd(II) rapidly and efficiently with maximum metal removal capacities of 34.13 mg/g and 60.24 mg/g, respectively. These values of heavy metal uptake at equilibrium were higher than the amount of Cu(II) and Cd(II) removal by free biomass (17.60 mg/g and 69.44 mg/g, respectively). Biosorption equilibrium data were best described by Langmuir isotherm model. The biosorption kinetics followed the pseudo-second order model and intraparticle diffusion equation. The results obtained suggest that the immobilized biosorbent holds great potential for wastewater treatment applications.

Removal of Heavy Metals from Aqueous Solution Using Rhizopus delemar Mycelia in Free and Polyurethane-Bound Form

This study assesses the ability of mycelia of Rhizopus delemar (both free and immobilized on polyurethane foam) to remove heavy metals from single-ion solutions as well as from a mixture of them. All experiments were conducted using 0.5-5 mm solutions of CuSO4·5H2O, CoCl2·6H2O and FeSO4·7H2O. Mycelia immobilized on polyurethane foam cells showed some times increase in uptake compared with that of free cells. Metal ions accumulation from a mixed solution was decreased slightly for cobalt and iron and considerable for copper ions. Heavy metal uptake was examined in the immobilized column experiments and more than 92% heavy metal removal (mg heavy metals removed/mg heavy metals added) from a mixed solution was achieved during the 5 cycles. During these experiments, the dry weight of the immobilized cells was decreased by only 2%. These results showed that immobilized mycelia of Rhizopus delemar can be used repeatedly for removal of heavy metals from aqueous solutions.

Effect of cadmium and copper on the production of citric acid byAspergillus niger

Copper and cadmium inhibited the growth as well as citric acid production (depending on the heavy metal concentrations) by citric-acid-producingAspergillus niger. Activity of citrate synthase was connected with citrate synthesis in the absence as well as in the presence of heavy metals. The activity of aconitase, and both NAD- and NADP-isocitrate dehydrogenases was strongly inhibited by copper. The contents of DNA and proteins in the cells decreased but the contents of lipids and polysaccharides increased considerably in the presence of both heavy metals.

Phosphatase activity and copper uptake during growth of Aspergillus niger

Abstract The fungus Aspergillus niger produced extracellular and cellular acid phosphatase activities during growth in the presence or absences of copper ions in the medium. The levels of both phosphatase activities depended on the copper concentrations in the medium. Enzyme activities were maximal at the mid-exponential growth phase, as well as at the higher copper concentration and decreased as growth time increased from 12 to 48 h. The total uptake of copper (II) by mycelia, growing at the presence of copper was highest when the levels of enzyme activities were maximal. Between 10 and 20% copper (II) was not removed by washing in 0.1 M H2SO4, suggesting that this copper (II) was bound intracellularly by mycelia of different age. On the other hand, copper ions slightly inhibited cellular acid phosphatase activity of Aspergillus niger with a Ki of 0.89 mM. Acid phosphatase overproduction, as well as copper uptake of mycelia indicated a possible participation of acid phosphatases in the resistance of the fungal strain to the copper toxicity.

Copper (II) Accumulation And Superoxide Dismutase Activity During Growth Of Aspergillus Niger B-77

The influence of copper (II) ions on the growth, accumulation properties and superoxide dismutase (SOD) activity of a growing culture of Aspergillus niger B-77 were studied. Microbial growth, the level of copper (II) accumulation and SOD activity depended on the initial copper (II) concentration. Aspergillus niger is able to accumulate large amounts of copper (II) from the nutrient medium with 200 mg.l-1 copper (II) ions without loosing its biological activities. Addition of copper (II) ions increased the SOD activity in the growing cell cultures. The changes in enzyme activity induced by heavy metal ions might be used as an indicator of intracellular oxy-intermediate generation in a cell culture growing under stress conditions

Biosorption of binary mixtures of copper and cobalt by Penicillium brevicompactum.

Abstract This work reports on a study of the biosorption of copper and cobalt, both singly and in combination (in equimolar concentrations), by the resting cells of Penicillium brevicompactum. Equilibrium batch sorption studies were carried out at 30 °C and pH 5.0 for a contact time of 1 hour to guarantee that equilibrium was reached. The equilibrium data were analyzed using the Langmuir and Freundlich isotherms. The adsorption of binary mixtures of heavy metal solutions on the fungal biomass was found to be of competitive type where the adsorption capacity for any single metal decreased in the presence of the other. The cobalt ions showed a higher affinity for Penicillium brevicompactum than the copper ions.

Copper accumulation byAspergillus awamori

Aspergillus awamori accumulated Cu2+ from aqueous solutions. The level of copper uptake was dependent on the ambient metal concentration. The process consisted of two phases: a fast initial phase and a slower secondary phase. Chelation of these ions occurs by chemical, equilibrated and saturable mechanism, following the mathematical models of Langmuir and Freundlich, with better performance on the Langmuir model. Data transformation allowed us to calculate the kinetic constants of the sorption reaction.

Bioaccumulation of Heavy Metals by Microorganisms

ABSTRACTTen yeast and mould strains from the culture collection of the Institute of Microbiology were tested for their abillity to accumulate heavy metal ions from aqueous solutions. The selective accumulation of Cu, Cd, Co and Zn ions by various microorganisms has also been examined. Cadmium was accumulated selectively. From these 10 species of microorganisms tested a high heavy metals absorbing ability was found in Rhizopus delemar, Penicillium brevicompactum and Saccharomyces cerevisiae.

INTELLIGENT SOFTWARE ANALYZER DESIGN FOR PARAMETERS EVALUATION OF TERNARY HEAVY METAL IONS REMOVAL BY IMMOBILIZED FUNGAL BIOMASS

In this paper the fuzzy logic method improved by adaptive learning of a fuzzy inference system, based on anfis, was used to demonstrate a software analyzer design for parameters evaluation of ternary heavy metal ions removal. The studied process was conducted to investigate metal binding ability of the novel hybrid hydrogel, obtained by entrapping Penicillium cyclopium biomass into chemically cross-linked poly (vinyl alcohol) (PVA) network toward Cu2+, Co2+ and Fe3+ from ternary aqueous solution. The performance of the biosorbent was evaluated by determining the values of heavy metal uptake and heavy metal removal efficiency in the ternary metal mixture. The innovative immobilization technology developed provides an attractive strategy for the developing high-affinity biosorption system for the treatment of wastewater containing heavy metals in low concentration. The obtained results of both — the studied process and software analyzer design and implementation are illustrated and discussed.

Phenol biodegradation by fungal cells immobilized in sol-gel hybrids.

The capability of cells of the fungus Aspergillus awamori, either free or immobilized in hybrid sol-gel material cells, for phenol biodegradation was demonstrated. Phenol was present in the reaction mixture as the sole carbon and energy source, and its decomposition was followed in repeated batch degradation experiments. Atomic force microscopy provided information on the development of self-organizing structures in the materials synthesized by the sol-gel method. Phenol biodegradation was mediated only by the fungal cells, and no absorption by the hybrid matrix was observed. Ten cycles of phenol biodegradation using the immobilized cells system were conducted during which up to 2000 mg l-1 phenol was completely decomposed. Immobilized cells degraded phenol at 8.33 mg h-1, twice as fast as free cells. The good performance of the immobilized fungal cell system is promising for the development of an efficient technology for treating phenol-containing waste waters