Mihail Iliev

Biogenic iron compounds: XRD, Mossbauer and FTIR study

AbstractMaterials based on biogenic iron oxides, which are a product of the metabolic activities of the neutrophilic iron-oxidizing bacteria (NIOB) from Sphaerotilus-Leptothrix group, were investigated. Natural microbial probes were collected from freshwater flow from Vitosha Mountain (Bulgaria) and cultivated under laboratory conditions in respect to select suitable cultures and conditions (nutrition media) for biomaterial accumulation of biogenic oxides. Samples were studied by physicochemical methods: X-ray diffraction, Mossbauer spectroscopy and IR spectroscopy. Their phase composition and physicochemical properties were obtained. Presence of both amorphous and crystal phase (ultra- and highly dispersed particles) was proved. Iron-containing compound in the natural biomass consists of α-FeOOH. The cultivated materials have more complex composition with iron-containing ingredients as α-FeOOH, Γ-FeOOH, Γ-Fe2O3 and Fe3O4. The sample of natural biomass was tested in reaction of CO oxidation and it showed potential to be used as catalyst support.

Study on the Composition of Biogenic Iron-Containing Materials Obtained Under Cultivation of the Leptothrix sp. on Different Media

The biogenic iron oxide/hydroxide materials possess useful combination of physicochemical properties and are considered for application in various areas. Their production does not require special investments because these compounds are formed during cultivation of neurophilic iron bacteria. Bacteria from genus Leptothrix develop intensively in the Sphaerotilus-Leptothrix group of bacteria isolation medium and feeding media of Fedorov and Lieske. These media are different in their composition which determined the present study as an attempt to clear up the reasons that define the differences in the composition of the laboratory-obtained biomasses and the natural biomass finds. FTIRS, Mössbauer spectroscopy, and XRD were used in the research. Comparative analysis showed that the biomass and control samples contain iron compounds (α-FeOOH, γ-FeOOH, β-FeOOH, γ-Fe2O3) in different ratios. The biomass samples were enriched in oxyhydroxides of higher dispersion. Organic residuals of bacterial origin, SO4, CO3, and PO4 groups were registered in the biogenic materials.

Numbers and Arrival Dynamics of Communally Roosting Magpies (Pica Pica) in the Dendrological Park of the University of Forestry—Sofia, Bulgaria

ABSTRACT This is the first annual study of a Eurasian magpie communal roost in Bulgaria. The roost is situated in the Dendrological Park of the University of Forestry—Sofia. The study was carried out in 2007–2008. We ascertained that magpies used to visit the communal roost all year round. The maximum number of birds recorded on one visit was 1405 birds (December 2007) and the minimum number was 139 birds (July 2007). The number of birds sleeping in the communal roost declined in the beginning of the breeding season because the birds started sleeping in their nests or near to them. The average number of birds sleeping in the communal roost during the summer was 32,33% from these in winter. We suggest these were non-breeding and birds whose breeding territory overlapped with the area of the communal roost. Despite significant fluctuation in the number of roosting birds during different seasons, the arrival dynamics of magpies were markedly uniform across all seasons with the exception of spring. The number of birds increased gradually in the first intervals of the study and they reached their peak in the interval 30–15 minutes before sunset and then decreased similarly. However, in spring proportionally more birds arrived on the roost in the interval 15 minutes before to 15 minutes after sunset without any decrease after sunset. Having arrived on the communal roost before sunset, the magpies perched in the crowns of the tallest trees and concentrated in the highest NE part of the roost (altitude 591 m). In the twilight period the birds were shifting their place to the lowest parts (altitude 587 m) which were highly overgrown with dense shrubs. We suggest that the Park has become important for the magpie because of lack of exploitation and we think that returning the intensive exploitation might force the birds to change the roost.

Diversity and biocide susceptibility of fungal assemblages dwelling in the Art Gallery of Magura Cave, Bulgaria

*pedro-maria.martin-sanchez@bam.de Citation:

Bioleaching of a Copper Sulphide Ore at Different Temperatures

Copper sulphide ore containing 0.37% Cu, with chalcopyrite as the main copper-bearing mineral, was leached in percolation columns containing 20 kg of ore crushed to minus 20 mm at different temperatures 18, 50 and 70°C. The columns were inoculated with cultures of mesophilic, moderately thermophilic and extremely thermophilic chemolithotrophic bacteria, respectively. Different variants of leaching with respect to the composition of the leached solution and the rate of irrigation of the ore were applied at each of the temperatures above-mentioned. The best results were achieved at leaching carried out at 70°C, with periodic additions of ferric ions, nutrients and bacterial cells by leach solutions prepared in a separate BACFOX-type unit, and by application of enhanced aeration of the ore by air enriched in CO2. 82.1% of the copper was leached in this way within a period of 230 days, while the highest Cu extraction achieved at 18°C was 28.0% and that at 50°C was 55.4%, within the same period of time.

PCR Detection and 16S rDNA Sequence Analysis of Different Acidithiobacillus Ferrooxidans Isolates

ABSTRACT Acidithiobacillus ferrooxidans is one of the most important microorganisms involved in bioleaching, acid mine drainage and biodesulphurization of coals. In this study A. ferrooxidans is detected in liquid samples using specific primers for 16S rDNA PCR. The applied PCR technique is accomplished using template DNA from pure cultures of the microorganisms. PCR amplification products were subjected to bioinformatical analysis. The results obtained from these analyses are a good foundation for further molecular experiments with different A. ferrooxidans isolates.