Peculiarities of a Colloidal Polysaccharide of Newly Isolated Iron Oxidizing Bacteria in Armenia

Microorganisms belonging to different systematic and physiological groups produce various intra- and extracellular polysaccharides, which both play an important role in the life of microorganisms and have great practical application. Iron and sulfur oxidizing bacteria produce capsular (EPS) and colloidal polysaccharides. At present the properties and functional role of EPS are well studied. However, the properties of the colloidal polysaccharides produced by iron oxidizing bacteria have not been sufficiently explored. A new iron oxidizing bacteria Leptospirillum ferriphilium CC was isolated from sulfide ores of Armenia. Its morphological and physiological features have been studied. A colloidal polysaccharide has been isolated with the use of an original method developed by the authors, and its physical and chemical properties have been studied. It has been shown that the colloidal polysaccharide consists of three different monomers- glucose, fructose, mannose.. Investigations with a complex method of optical polarization microscopy and analytical programs allowed determining the size, shape change, perimeter, degree of hydratation and crystallization at 0.07% and 0.04% of polysaccharide concentration. It was shown that the size of a polysaccharide colloidal particle does not much depend on polysaccharide concentration, however, the number of identical colloidal formations is dependent on the concentration of polysaccharide

Bio-Assisted Leaching of Non-Ferrous Metals from Waste Printed Circuit Boards-Importance of Process Parameters

peer reviewedThis article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BYBaCLEM projec

VIOLATIONS OF GRAMMATICAL AND MORPHOLOGICAL NORMS IN THE INTERNET ARMENIAN

Speakers not always maintain all grammatical norms in oral speech. However, before the Internet came into being the written public speech was predominantly based on preservation of Armenian language norms, which was largely a subject to censorship and editing. Today the situation has dramatically changed. Alongside with numerous mistakes (spelling, punctuation, lexical), a great variety of cases regarding the violation of grammatical norms are evident. The given article is dedicated to the study of these cases. Particularly, the mistakes concerning the plural, the incorrect usage of dates, pronouns and link words, cases of violation of verbal norms, as well as penetration of some common expressions of everyday language into written speech have been considered

Biological extraction of Cu and Ni from printed circuit boards via redoxolysis with concomitant material characterization

peer reviewedAmong the different types of secondary post-consumption wastes, E-wastes or waste electrical and electronic equipment represent the fastest growing and most problematic waste stream with printed circuit boards (PCBs) constituting its major ingredient. Results from the extraction of Cu and Ni from PCBs using biogenic Fe2(SO4)3 obtained from the original isolate Acidithiobacillus ferrooxidans 61 (KM819692) are presented. At. ferrooxidans 61 was grown at a temperature of 30 °C in a modified 9K medium supplemented with ferrous iron. Two-stage bioleaching was carried out at 600 rpm and 40 °C. Experiments were performed at 10 % of pulp density (PD) with 48-hour duration (each stage of 24 h), under pH 1 and 20 g/L Fe3+. Under these conditions, overall recovery of Cu and Ni of 95% and 87% respectively was achieved. The obtained results indicate that non-ferrous metals in PCBs may be efficiently leached within two-stage bioleaching coupling bio-oxidation to subsequent redoxolysis. Scanning electron microscope (SEM) images acquisition and elemental mapping were performed to assess the liberation degree of essential phases after size-reduction steps and their implication on bioleaching efficiency

Bioleaching of metals from e-waste using immobilized biomass of mesophilic Acidithiobacillus ferrooxidans

Among the secondary post-consumption wastes, e-wastes represent the fastest growing waste stream in the world being heterogeneous and diverse in terms of structure and composition. Consequently, it is difficult to feed such waste into conventional recycling streams. Biometallurgy could prove a competitive and applicable technique for recovering valuable metals from these materials. The objective of the study is to test the feasibility of biometallurgy for recycling secondary raw materials, rendering the presently uneconomic raw materials economically viable, thus contributing directly to the circular economy. Long-term objective is to study the peculiarities of bioleaching of secondary raw materials, reveal the role of bacteria in these processes and develop the concept on the mechanism of bioleaching of secondary raw materials. Comparative chemical leaching of printed circuit boards (PCBs) by ferric sulfate Fe2O12S3xH2Osolution and biogenic Fe3+ obtained by immobilized biomass ofAcidithiobacillus ferrooxidans 61 (Armenia) and Acidithiobacillus GR1 (Bulgaria) has been performed. The intensity of zero valent copper oxidation was correlated to the ratio of Fe3+/Fe2+ ions in the solution. It was revealed that recovery of metals from PCBs by biogenic Fe3+ occurred 2-3 times more intensively than that by Fe2O12S3xH2O solution. The use ofFe2O12S3xH2O solution for leaching of PCBs resulted in intensive precipitation of Fe3+ andgeneration of jarosite, while in case of biogenic Fe3+ the amount of jarosite was significantly lower. It is supposed that Fe3+ in biogenic solution is mainly in the form of complexes with organic compounds produced by bacteria, which prevent its precipitation as jarosite. It is as-sumed that chemical leaching by biogenic Fe3+ integrated into the processes of leaching of PCB's may contribute to intensification of extraction of copper and other valuable metals from different secondary resources

ASSESSMENT AS A SIGNIFICANT COMPONENT IN EDUCATIONAL PROCESS

The article discusses assessment as a significant component of educational process. The assessment mechanisms and peculiarities are listed in the framework of the recent reformations in educational sphere. In this context assessment is investigated as educational outcome or everlasting and constant evidence collection, analysis and usage. The authors prove the fact that assessment should be for the learner and with the learner as an ongoing process

Adhesion to Mineral Surfaces by Cells of <i>Leptospirillum</i>, <i>Acidithiobacillus</i> and <i>Sulfobacillus</i> from Armenian Sulfide Ores

Bioleaching of metal sulfides is an interfacial process where adhesion and subsequent biofilm formation are considered to be crucial for this process. In this study, adhesion and biofilm formation by several acidophiles (Acidithiobacillus, Leptospirillum and Sulfobacillus) isolated from different biotopes with sulfide ores in Armenia were studied. Results showed that: (1) these bacteria adhere to pyrite surfaces to various extents. A correlation between pyrite biooxidation and adhesion of S. thermosulfidooxidans 6, L. ferriphilum CC, L. ferrooxidans ZC on pyrite surfaces is shown. It is supposed that bioleaching of pyrite by S. thermosulfidooxidans 6, L. ferriphilum CC, L. ferrooxidans ZC occurs by means of indirect leaching: by ferric iron of bacterial origin; (2) cells of At. ferrooxidans 61, L. ferrooxidans ZC and St. thermosulfidooxidans 6 form a monolayer biofilm on pyrite surfaces. The coverage of pyrite surfaces varies among these species. The order of the biofilm coverage is: L. ferrooxidans ZC &#8805; At. ferrooxidans 61 &gt; St. thermosulfidooxidans 6; (3) the extracellular polymeric substances (EPS) analysis indicates that the tested strains produce EPS, if grown either on soluble ferrous iron or solid pyrite. EPS are mainly composed of proteins and carbohydrates. Cells excrete higher amounts of capsular EPS than of colloidal EPS. In addition, cells grown on pyrite produce more EPS than ones grown on ferrous iron

Sequential biologically assisted extraction of Cu and Zn from printed circuit boards (PCB)

peer reviewedThe increased production and use of electrical and electronic equipment leads to obsolescence and disposal problems, necessitating materials recovery and recycling. This paper reports results on metal bioleaching from printed circuit boards (PCBs) using chemolithotrophic bacteria isolated at different sulphide ore biotopes in Armenia. Different ways of generating lixiviants were investigated, namely using combination of Acidithiobacillus ferrooxidans 61 and Acidithiobacillus thiooxidans SO-1 bacteria generating biogenic Fe2 (SO4)3 and biogenic H2SO4. The sequence between these leaching agents permitted design of a 2-step process based on acidolysis and redoxolysis to leach non-ferrous metals from PCBs. To compare the efficiency of the sequential bioleaching of PCBs, several experimental runs were realised under the six modes at 10% pulp density. The flasks-based tests have witnessed almost complete recovery of Cu with the rest of the metals reaching extraction degree above 80%.BaCLE

Effect of Cell Lysis (CLs) Products on Acidophilic Chemolithotrophic Microorganisms and the Role of Acidocella Species

Acidophilic chemolithotrophic microorganisms (CMs) are widely used for bioleaching of mineral resources. However, the growth of bacteria and their leaching activity are often inhibited (restricted) by organic components, e.g. lysates and exudates. The aims of this study were to examine the extent of cell lysis (CLs) inhibition on acidophilic microorganisms and to identify microorganisms that can utilize CLs products and eliminate their inhibition effect on acidophilic microorganisms. Specifically, it was revealed that Acidithiobacillus caldus was severely inhibited at 5% CLs products, whereas A. ferrooxidans and Leptospirillum ferriphilum are severely inhibited at 20%. It has been found that strains RBA and RBB of heterotrophic bacteria, isolated from anaerobic sludge, can biodegrade CLs products and when co-cultured with A. ferrooxidans, they can alleviate the toxic effect of CLs products under low pH (2–3). It has been shown that besides CLs, isolated strains can grow on glucose, glycerol, yeast extract, citric acid, and tryptone soya broth with an optimum temperature of 35°C and a pH of 3. The strains showed the ability to reduce ferric ions to ferrous ions when glycerol was used as a substrate after 2 days under both aerobic and anaerobic conditions. On the basis of morphophysiological and molecular biological studies, the isolated strains RBA and RBB were identified as Acidocella spp

Bioleaching of Sulfide Minerals by <i>Leptospirillum ferriphilum</i> CC from Polymetallic Mine (Armenia)

A strain of Leptospirillum sp. CC previously isolated from Akhtala polymetallic ore (Armenia) was studied. The main morphological and physiological characteristics of CC were revealed. The optimal growth temperature was 40 °C and optimal pH 1.5. A phylogenetic analysis based on 16S rRNA gene sequences (GenBank ID OM272948) showed that isolate CC was clustered with L. ferriphilum and possessed 99.8% sequence similarity with the strain L. ferriphilum OL12-2 (KF356024). The molar fraction of DNA (G + C) of the isolate was 58.5%. Bioleaching experiment indicates that L. ferriphilum CC can oxidize Fe(II) efficiently, and after 17 days, 44.1% of copper and 91.4% of iron are extracted from chalcopyrite and pyrite, respectively. The efficiency of L. ferriphilum CC in pyrite oxidation increases 1.7 times when co-cultivated with At. ferrooxidans ZnC. However, the highest activity in pyrite oxidation shows the association of L.ferriphilum CC with heterotrophic Acidocella sp. RBA bacteria. It was shown that bioleaching of copper and iron from chalcopyrite by association of L. ferriphilum CC, At. ferrooxidans ZnC, and At. albertensis SO-2 in comparison with pure culture L. ferriphilum CC for 21 days increased about 1.2 and 1.4–1.6 times, respectively