bluuebunny/crossref_metadata_2025 huggingface dataset:
Promoting Sustainable Development Through Engineering and Technology Capacity Building in Africa: The Role of DTCA
Authors: Bassi S.Y.
Published: March 2009

To achieve meaningful and sustainable development of Africa, the continent must of
necessity look inwards particularly in the areas of Science, Engineering, technology capacity
building; and this is in view of the growing trends in globalization. There must be an active
collaboration and networking between research and industry on the one hand and between
researchers across the nations of Africa. This will promote technical cooperation which is sine qua
non to the development of the continent. A survey project on viable technological invention and
innovation in Engineering Research and Development (R&D) in Nigeria and their impact on
industry development by the Directorate of Technical Cooperation in Africa (DTCA) indicates that:
(a) though quite some achievements have been recorded in this sector, most of the inventions and
innovations are still at the level of incubation: (b) funding is a critical factor limiting development
of the Engineering Research and Development (R&D) sector: (c) there is minimum linkage and
collaboration among researchers, as well as between Research and industry, (d) the engineering
base remains small, fragmented and operating below the thresholds that would enable it make any
meaningful impact on industrial development: (e) brain drain is a key challenge as some of the best
and brightest engineers migrate to greener pastures mainly in the western countries. This paper
review the result of this project and argues for concerted efforts by all relevant stakeholders to
promotes full development and commercialization of viable inventions and innovations towards the
rapid development of Africa. The role of the DTCA in this is also highlighted.
The Planning of Continuity of Technological Education in West Africa Using Critical Path Method: Nigeria and Ghana as Case Studies
Authors: Adejuyigbe Samuel B.
Published: March 2009

In this paper the author used his personal experience having passed through all the facets
of technological education specializing in Mechanical Engineering to solve the problem of noncontinuity
of technological educational system. Critical Path Method (CPM) was used to develop a
model for the continuity of Technological Education using Nigeria and Ghana as a case study. The
paper completely eliminates the terminal certificates awarded in some Nigerian and Ghanaian
Technological Institutions.
Other educational lines like: Education, Art and Sciences were compared with that of Technological
line and solutions were proffered to the identified problems.
Influence of Surface Topography on Corrosion of Stainless Steel AISI 304 Turned Surfaces with Different Cutting Conditions
Authors: Hassiotis N. , Petropoulos G. , Hatzopoulos C. , Vaxevanidis N.
Published: March 2009

In this study, the correlation between corrosion behaviour and formations, and topographic
characteristics of machined surfaces of stainless steel AISI 304 is investigated. Face turning was
performed for combinations of cutting conditions, leading to four differing surface patterns
owing to regular chip formation, very small chip thickness effect and built-up-edge formation.
To simulate industrial and environmental corrosion two corrosion tests were applied i.e. alternate
immersion method and exposure to FeCl3 solution. Different corrosion behaviour was revealed
through stereoscopic examination of the surfaces with regard to machining conditions and the
best global anti-corrosive performance was exhibited by the surfaces generated under regular
chip formation.
Effect of Particle Size on Some Properties of Rice Husk Particleboard
Authors: Osarenmwinda J.O. , Nwachukwu J.C.
Published: March 2009

The purpose of this study was to determine the effect of particle size on the mechanical
properties (Modulus of Elasticity, Modulus of Rupture, and Internal Bond) and physical properties
(thickness swelling and water absorption) of rice husk particleboard. The particle sizes used were
1.0mm, 1.18mm, 2mm, 2.36mm and 2.80mm. Each was mixed with a constant resin (urea
formaldehyde) concentration of 20% of oven dry weight of rice husk particles. The results showed
that as the particle size increased, the particleboard’s mechanical and physical properties decreased.
For example, the modulus of elasticity, modulus of rupture, internal bond, thickness swelling and
water absorption for 1.0mm particle size particleboard were 1590N/mm2, 11.11N/mm2,
0.28N/mm2,10.90% and 38.53% respectively, while for 2.8mm particle size they were
1958N/mm2,14.2N/mm2, 0.44N/mm2, 11.51% and 47.21% respectively. Overall results showed that
particleboard made from rice husk exceed the EN standard for modulus of elasticity, modulus of
rupture, internal bond. However, thickness swelling values were poor. Hence, the smaller the
particle size the better the properties of the particleboard.
Design of Process Layout for a Pilot Alkyd Resin Production Plant
Authors: Igboanugo A.C. , Amiebenomo S.
Published: March 2009

There are several reasons why industrial engineers need to optimize process layout
designs. This paper points out the justification and discusses the qualitative and quantitative
techniques involved in the determination of an optimal process layout for a pilot alkyd resin and
its end products manufacturing system. It also spotlights practical decisions required for
achieving optimality in the design process. It is the belief of the authors that with some
improvements on the final layout, our proposed layout will be a ballpark of eco-factory moored
on green manufacturing.
Potential Use of Waste Paper/Sludge as a Ceiling Board Material
Authors: Folorunso O.P. , Anyata B.U.
Published: March 2009

A material was made from cement/waste paper/sludge mixture and tests were carried out
on it to ascertain its suitability as a ceiling board material. The tests included water absorption,
drying shrinkage, flexural strength, thermal conductivity, and compressive strength. The results
showed that the material possesses good properties as a ceiling board material.
Distribution of some Heavy Metals in Leachates from a Municipal Waste Dumpsite
Authors: Obahiagbon K.O. , Olowojoba G.B.
Published: March 2009

The distribution of heavy metals in leachates from a waste dumpsite was investigated.
Soil samples were taken from a major dumpsite in Edo State located at Oluku near the National
Institute for Oil Palm Research (NIFOR) and analyzed. The heavy metals considered were Iron,
Lead, Zinc, Mercury, Chromium, Cadmium, Arsenic, Nickel, and Copper. The concentrations, in
mg/l, of these heavy metals in the leachates from the soil samples over a distance of 80 meters were
determined using the Atomic Absorption Spectrophotometer (AAS). The following results were
obtained, the concentration of Iron ranged between 1.25-1.85 mg/l, Chromium: 0.01-0.07 mg/l,
Zinc: 0.45-3.45 mg/l, Copper: 0.01-0.03 mg/l, Lead, Mercury, Cadmium, Arsenic, and Nickel had
negligible values, i.e. less than 0.01 mg/l. From the results the concentrations of iron and zinc fell
within Federal Environmental Protection Agency (FEPA) limits.
Feasibility Study for Waste Incinerator Plant for the Production of Electricity in Harare,Zimbabwe
Authors: Mbohwa C. , Zvigumbu B.
Published: March 2009

Estimates of weight of general refuse generated in this country’s major cities vary, but in
Harare it is estimated at above 823 000 tonnes, which is mostly land-filled. This paper proposes the
incineration of combustible municipal waste to produce 40 MW of electricity and considers its
feasibility. This can give a waste reduction to as low as one tenth of the initial volume and is quite
effective in killing pathogens. The work involved use of questionnaires, interviews and access to
primary data at the Harare City Council. The positive and negative environmental and health
impacts, particularly relating to dioxins are discussed and solutions to pollution proposed.
Admixture of Used Engine Oil with DPK (Kerosene) as an Alternative Fuel for Foundry Shop
Authors: Fakolujo O.S. , Jimoh S.O. , Ighalo B.S.O.
Published: March 2009

This study presents the experimental results of using admixture of used engine oil and
kerosene as an alternative fuel in foundry shops. In this experiment, several proportions of used
engine oil (well filtered) and kerosene were measured to make 1000ml per mixture using a
calibrated beaker. Each mixture was fired in a furnacensuring atomization, ignition and
combustion in a timed set up. Results of the experiment showed that admixtures of 100%, 95% and
90% volume of used engine oil gave low pour point hence were incombustible. 85%, 80% and 75%
volume of used engine oil admixtures gave carburized flame. While 55% and below of used engine
oil volume of admixtures gave oxygenated flame. 57% - 70% volume of used engine oil admixtures
produced neutral flame which is ideal for melting. Of the latter proportions, 70% of used engine oil
admixture had the highest heat content 70,780 kj/kg and the lowest cost. Hence this admixture is
recommended as an effective admixture for fuel substitution in the foundry shop.
Ultrasonic Pulse Velocity for In Situ Measurement of Compressive Strength of Concrete
Authors: Chidolue C.A. , Chidolue B.A. , Umenwaliri S.N.
Published: March 2009

In this study, pulse velocities calculated from the time taken by pulses emitted by a
transducer to traverse a known thickness of the concrete is utilized in building up a correlation
between pulse velocity and strength of concrete cubes and between pulse velocity and age of
concrete. Three different arrangements of transmitters and receivers were studied to cover the
varieties of problems likely to be encountered on a site. These are direct transmission, semi-direct
transmission and indirect transmission. For a particular mix proportion and aggregate size a
calibration curve was obtained for in-situ testing of concrete. These curves can be used to
determine the relative in-situ strength of similar members or structures.
Improved Wastewater Treatment Using Carbon Dioxide
Authors: Enyi C.G. , Appah D.
Published: March 2009

This paper focus on the use of Carbon dioxide (CO2) instead of sulphuric acid (H2SO4) in
a modified wastewater treatment scheme. Over 90% of the vented CO2 from an ammonia plant was
used in this scheme, CO2 was directly injected into the wastewater to neutralize it, by reducing the
pH to acceptable standard (7.0). This was achieved because the CO2 produces carbonic acid
(H2CO3). The use of this process produced a better overall effluent quality of wastewater (pH, 7.56;
TDS, 155.15 ppm; Heavy metal, 1.49 ; ppm) as against the use of H2SO4 (pH, 8.77; TDS, 1000
ppm; Heavy metals, 2.90 ppm) which has to be purchased. Savings in operating costs amount to
N13,710,600 ($100,813.00) per year, with improved treatment efficiency. Additional long term
savings are projected because of reduced shutdown time. However, it was observed that it took 45
minutes longer to achieve this result with CO2.
Simulation Model for Assessing Operational Performance of Current Transformers
Authors: Sule I.
Published: March 2009

In determining the correct operation of relays of a protection scheme, proper
representation of instrument transformers and their behavior in conditions where there can be
saturation, is very critical. The main objective of this paper is to develop simulation model for
assessing the operational performance of Current Transformer (CT). In order to test the validity of
the developed model, three cases of CT operational conditions were considered, with data collected
from Gombe, 330/132/33kV PHCN substation. The simulation results revealed various
configuration performance responses that could affect relay protective schemes to different degrees.
The CT responses revealed that the secondary current and voltage were distorted when the core flux
linkages exceeded the set 9.2 pu saturation limit. It is concluded that the model developed for the
CT of interest yield satisfactory results.
Sliding Mode Control of Magnetic Levitation Vehicles
Authors: Kadalla A.S. , Onogu M.I.
Published: March 2009

The problem of precise control of the air – gap of magnetic levitation vehicles is
considered in this paper. A sliding mode controller is designed for the levitation control task.
Robustness of the controller was investigated using computer simulations. The results show that the
controller is robust to parameter variations of up to ±13% and can tolerate disturbances up to
±400N/Kg.
Investigation of Viscosity and Thermodynamic Properties on the Bioleaching Solution with and without Mesophilic Bacteria
Authors: Liu Mei Lin , Ruan Ren Man , Wen Jian Kang , Wang Dian Zuo
Published: March 2009

In this study, the viscosities and conductivities of bioleaching solution were determined by
Ubbelohde viscometer and conductivity meter, respectively. The mean ionic activity coefficients,
relative partial molar free energies of copper bioleaching solution at above experimental temperatures
ranging from 298 K to 313 K have been calculated. Simultaneously, these characters of copper
bioleaching solution were compared with and without mesophilic bacteria. The experimental data
showed that the viscosities and thermodynamic properties for bioleaching solution would be crucial
to minimize the third phase formation so as to increase extraction efficiency.
Process Enhancement of Bioleaching of Covellite Concentrate through Modification of Solution Potential
Authors: Zhou E. , Wen Jian Kang , Ruan Ren Man , Wang Dian Zuo
Published: March 2009

Based on the bioleaching mechanism and electrochemical studies of covellite, the
dissolution rate of covellite mineral is accelerated through increasing the redox potential (Eh) of the
leach. In the present work, some methods were adopted to enhance the bioleaching of covellite
concentrate (collected from Zijinshan copper mine, Fujian province, China) by adding different
oxidants such as pure pyrite, ferric ions and H2O2. The goal of this study was to provide appropriate
operating parameters for the industry application and increase the efficiency of the bioleaching of
copper mine. The results showed that the optimal way to increase the redox potential (Eh) level was
the addition of pure pyrite. This method could effectively raise the Eh of bioleaching process while
the effect of environmental change was negligible. It could quicken the leaching process and
enhance the final copper recovery through the addition of pyrite by 1:1 or 1:2 ratio of covellite
concentrate to pyrite.
Bioleaching of Multimetal Black Shale by Thermophilic Micro-Organisms
Authors: Langwaldt Jörg
Published: March 2009

In this work the leaching of black shale ore and froth flotation concentrates produced
from the black shale was studied. The complex black shale contained various sulphide minerals
(alabandite, sphalerite, pyrrhotite, pentlandite, violarite, chalcopyrite, pyrite). Concentrations of
base metals in the ore were Fe 13.2%, Mn 0.97%, Ni 0.3%, Zn 0.57%, Cu 0.23% and Co 0.03%.
The base metal content was two to three times higher in the flotation concentrate than in the ore.
Ore and concentrate were leached in shake flasks and stirred tank reactors at pulp density of 10 to
20%, pH 1.2 to 2.0 and 60 to 77°C. A thermophilic enrichment culture related to Sulfolobus
metallicus was applied. The pulp was aerated with ambient air and dinitrogen gas was used in a
control test. Experimental duration was from 12 to 49 days. Leaching of Mn, Fe, Zn, Ni, Cu, and Co
was up to 96, 52, 99, 99, 97 and 76%, respectively. Mn and Zn were rapidly leached within the first
2 to 3 days. In test with the ore, metal recovery was negatively affected by precipitate formation
towards the end of leaching period. The H2SO4 consumption was in the range of 177 to 346 g/kg
ore and 11 to 122 g NaOH/kg ore was consumed respectively. In bioleaching tests with flotation
concentrates the H2SO4 consumption was from 205 to 415 g/kg concentrate and 73 to 183 g
NaOH/kg concentrate was consumed, respectively. The final redox potential varied between 423
and 710 mV vs. Ag/AgCl. In experiments with fine ground ore, -50 8m, the ferric iron was at best
64% of dissolved total iron. Compared with coarser material (250-355, 710-1000 8m) leaching
proceeded best with fine ground ore -50 8m). In tests with coarse ore (710-1000 8m). dissolved
ferric iron was up to 97% of the total dissolved iron. Mechanical stirring and fine particles caused
increase of dead cell numbers during leaching. The study demonstrates that the thermophilic
enrichment culture can leach complex black shale ore at high pulp density and temperature.
Combined Test for Bioleaching Activities
Authors: Rohwerder Thore , Sand Wolfgang
Published: March 2009

Both, the employment of leaching bacteria for metal winning as well as the mitigation of
bioleaching processes at AMD/ARD sites, require reliable monitoring methods for assessing
bacterial activities. Therefore, we have developed a robust and rapid test system combining two
sensitive analytical techniques: quantification of heat evolution by microcalorimetry and
determination of all relevant inorganic sulfur species by chromatographic methods (IC and HPLC).
Generally, only about 1 g of sample is sufficient for a complete analysis. The combined test has
been applied to various leaching biotopes such as bioreactors, columns, heaps and natural sites. The
bacterial activity of diverse sulfidic materials such as lignite and coal wastes, pure metal sulfides
and complex ores has been investigated. In our labs, microcalorimetry can be performed in the
range of 5 to 80 °C, covering most of the temperature spectrum of leaching bacteria. Hence, the
heat evolution values of samples as a direct measure for calculating leaching rates can be obtained
at nearly all relevant in situ temperatures. The combination with sulfur species determination results
in additional information on leaching mechanisms (thiosulfate or polysulfide pathway) and general
leaching performance (e. g. accumulation of sulfur intermediates).
Study on Selective Depression of Pyrite during Copper Bioleaching
Authors: Ruan Ren Man , Zhou Gui Ying , Wen Jian Kang
Published: March 2009

During Zijinshan copper heap bioleaching, pyrite was leached in plenty resulting in high ferric concentration in solution. This affected bioleaching and extraction processing greatly. The paper studied the factors influencing in the course of leaching of pyrite and a mixture of chalcocite and pyrite respectively. It focuses on the effect of the redox potential for copper bioleaching so as to find key factors affecting the dissolution difference between chalcocite and pyrite. The experiment results showed that redox potential is an important influencing factor in bioleaching. Copper and pyrite extents of the leaching process were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). It is indicated that copper can be selectively bioleached by controlling redox potential of bioleaching. The conclusion will provide theoretic foundation on balance of acid and iron during bioleaching for copper of higher S/Cu ratio. A simple sulfide, pyrite and chalcocite, were selected as test minerals. The samples were obtained from rich mineral in Zijin Mine. The concentrated samples were milled to obtain the size fraction of 320 mesh percent of 90. Bacterium culture: 9K culture medium contained the following composition in kg/m3 distilled water: (NH4)2SO4, 3.0; K2HPO4·3H2O, 0.5; KCl, 0.1; MgSO4·7H2O, 0.5; Ca(NO3)2·2H2O, 0.01. The initial ferrous concentration was 9.0g/L, the initial pH was adjusted to 1.6, and the temperature set at 30°C. The rotation speed of shaking bed was 150r/min. A three-day-old inoculum previously grown in medium was used in bioleaching process. A 5% inoculum was added to give an initial bacteria concentration in the medium was (3-6)×107 cells/m3. The experiments investigated factors influencing bioleaching including ferrous concentration and redox potential during bioleaching. The extent Cu leached was over 90%. Cu leached velocity increased as redox potential turned higher. Cu leached velocity rapid increased at redox potential 700mV. During chalcocite and pyrite bioleaching, redox potential is important factor to influence of bioleaching rate and the results showed that pyrite and chalcocite bioleaching rate was correlated with redox potential. It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching. It can be concluded that: (1) Pyrite and chalcocite bioleaching rate was correlated with redox potential. Redox potential was shown to be the key factor affecting the dissolution difference between chalcocite and pyrite. (2) Chalcocite and pyrite leaching efficiency were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). (3) It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching.
First Evidence of Active Sulphate Reduction in a Lignite Mine Dump Site at Low pH Values – the Plessa Site
Authors: Storch Annett , Tröger Katja , Hoth Nils , Knöller Kay
Published: March 2009

It has been postulated that bacterial sulphate reduction is related to pH-values above 5.5
(e.g. [1]). First investigations for the 80-year old dump Plessa in the Lower Lusatian mining district
(East Germany) show evidence for active sulphate reduction. Mining dump waters from the Plessa
site have pH values of 2.4 to 4.9 and pe values between 2 and 6. Measured sulphide concentrations
range from 50 to 1200 -g/L. The influence of bacterial sulphate reduction on the development of
sulphate concentrations in the dump waters is supported by increasing δ34S and δ18O values with
decreasing sulphate concentrations. These findings document that sulphate reduction under natural
conditions is not exclusively related to neutral pH values and strongly reducing conditions.
Furthermore the tertiary organic matter contained in the dump sediments is the main carbon source
for sulphate reducing bacteria.
Optimization of ROM Sulfide Leaching at Anglo American Chile Los Bronces Division
Authors: Saldívar Egidio , Zárate Gabriel
Published: March 2009

Los Bronces has two ROM dump leach operations called Leach I and Leach II.
Leach I was commissioned in 1998 and currently produces 12,700 ton per year. The copper
mineralization in these dumps is largely sulfides, namely 60% chalcocite/covellite, 30%
chalcopyrite and the balance is oxides. The Leach II plant, commissioned in early 2002, was
built to treat around 700 million ton of marginal ore having 0.45% total copper. The copper
mineralogy of this material is estimated to be 70% chalcopyrite, 20% chalcocite/covellite and
the balance oxides. Current copper production is 33,700 ton per year.
Early in 2004 it was decided to conduct a complete column test work program, aimed at
reducing power, acid and lime consumption at the Leach II plant. The results of this work,
partially reported at IBS 2005, have been successfully applied to the commercial operation
since the end of 2005. As a consequence, the projected reduction in operating costs for 2006
of US$ 5.5 million was accomplished.
The main results of the column test work program, the modifications implemented together
with the results obtained at the operation, including a molecular characterization of the
microbial population, are discussed in this paper.
Bioremediation of Acid Mine Drainage in an Uranium Deposit
Authors: Groudev Stoyan N. , Georgiev Plamen S. , Spasova Irena , Nicolova Marina
Published: March 2009

Acid drainage waters generated in the uranium deposit Curilo, Bulgaria, were treated by means of different passive systems such as natural and constructed wetlands, alkalizing limestone drains, permeable reactive multibarriers and a rock filter, used separately or in different combinations. The waters had a pH in the range of about 2 – 4 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, nickel, cobalt, iron, manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in agriculture and/or industry. The water flow rate through the individual systems was different and not stable, and varied in the range approximately from 0.02 to 1.5 l/s. Efficient removal of pollutants was achieved by means of these systems during the different climatic seasons, even during the cold winter months at water and ambient temperatures close to 0 oC. The removal was due to different mechanisms but microbial sulphate reduction, biosorption by living and dead plant biomass and chemical neutralization played the main roles.
Comparison of the Bioleaching Effect of Mesophilic (35°C) and Thermophilic (45°C) Bacteria on the TIZAPA Tailings
Authors: Rivera-Santillán R.E. , Becerril-Reyes V.
Published: March 2009

The exploitation of mineral deposits generates large amounts of wastes such as fine size particles,
known as tailings. Mine wastes are characterized by the presence of pyrite, pyrrotite, galene,
sphalerite, chalcopyrite and arsenopyrite. One of the most important environmental problems
derived from the treatment and disposition of mining tailings is acid mine drainage (AMD) which
results from the oxidation of the sulfurous minerals contained in these tailings. The acid generated
is produced by a series of complex chemical reactions; the production rate is controlled by leaching
microorganisms, which are present mining processes. In this work the bioleaching kinetics of heavy
metals such as Cu, Fe, Zn, Cd, Pb, Ni and As, from a Tizapa tailing sample in presence of
mesophilic and moderately thermophilic bacteria were studied and compared. The microorganisms
used in this work were previously adapted to the tailing sample by the conventional method of
successive steps. The percentage of dissolution of heavy metals at 45°C was smaller than at 35°C
and the value of parameters such as redox potential and bacterial growth increased with
temperature. Bioleaching studies were compared with the corresponding control systems.
Novel Steel Corrosion Protection by Microbial Extracellular Polymeric Substances (EPS) – Biofilm-Induced Corrosion Inhibition
Authors: Grooters Mariël , Harneit Kerstin , Wöllbrink Marcel , Sand Wolfgang , Stadler Reinhard , Fürbeth Wolfram
Published: March 2009

Microbially influenced corrosion (MIC) of steel has gained increasing attention in recent years because the damage caused by this process is a significant cost factor for industry. Consequently, inhibition of corrosion and especially the development of corrosion protective films is an important present-day research topic. In this connection, application of microbially produced EPS for mitigating steel corrosion is an innovative idea. However, observations of ”protective” biofilms on metallic surfaces have been previously reported. Their inhibiting effect is generally thought to be caused by oxygen depletion or the formation of passivating layers. In contrast to many conventional corrosion protective methods, EPS or EPS-derived agents would be a cheap and environmentally friendly solution. Extensive research activities are still required, before biofilms or cell-free EPS can be used for corrosion protection on larger scale. In this study, we are developing a novel EPS-based corrosion protection method for unalloyed and corrosion resistant steel in aqueous media, which is based upon the application of microbial metabolic products. EPS of various sulfatereducing bacteria and other microorganisms are investigated for their inhibiting effect. The extent of such inhibition is evaluated in a model test system, in which different steels are subjected to corrosive conditions under sulfate-reducing conditions. To elucidate the protective mechanisms, comparative analyses of the chemical composition of the applied EPS are performed.
Study of the Attachment Behaviour of Different Strains of Acidithiobacillus spp. to Pyrite
Authors: Mafanya Kanyisa Z. , Rohwerder Thore , Sand Wolfgang
Published: March 2009

Attachment to metal sulfide surfaces is a prerequisite of bioleaching activity via the
contact mode [Rohwerder et al.: Appl. Microbiol. Biotechnol. Vol. 63 (2003), p. 239]. Until now,
the mechanisms and possible variations of this attachment process among leaching bacteria is not
well understood. Therefore, we are studying the diversity in the attachment behaviour of different
strains of the genus Acidithiobacillus, which is one of the main bacterial group involved in the
bioleaching of metal sulfides. Among the species At. ferrooxidans, cells of the type strain (ATCC
23270) were found to attach the least. Whereas bacterial cells of strains A2 and R1 attached the
most. Other strains that were investigated in this study included At. ferrooxidans D-26 and R7.
Highly likely, these strains exhibit different attachment behaviour due to specific variations in their
extracellular polymeric substance (EPS) composition as loss of part of the EPS has previously been
observed to have a negative effect on attachment and bioleaching activities. Differences in several
EPS parameters such as the amount of complexed Fe(III) ions and the sugar composition are
possible reasons for the observed strain-specific attachment behaviour. In addition to attachment
assays and microscopic studies (AFM and epifluorescence), leaching activities of the strains were
comparatively investigated by short-term as well as growth experiments.
Regulation of the Arsenic Oxidation Encoding Genes of a Moderately Acidophilic, Facultative Chemolithoautotrophic Thiomonas sp.
Authors: Slyemi Djamila , Ratouchniak Jeanine , Bonnefoy Violaine
Published: March 2009

At the abandoned mining site of Carnoulès (Gard, France), weathering of the arsenopyrite rich tailings leads to the formation of acidic effluents heavily loaded with arsenite (As(III)). However, further downstream, the As(III) concentration decreases while the sediments are richer in arsenate (As(V)). A Thiomonas sp. able to oxidize arsenite to arsenate has been isolated and characterized. The aoxA and aoxB genes encoding the two subunits of this enzyme belong to an operon. Analysis of the genome sequence (Genoscope, Ivry, France) shows that this operon encodes also two cytochromes c, which could be the physiological partners of the arsenite oxidase, and a transcriptional regulator belonging to the metalloregulator ArsR/SmtB family, which could control the expression of the aox operon. The expression of this operon is higher in the presence than in the absence of As(III) and appears also to be repressed in the presence of thiosulfate, a more energetic substrate.
The Effect of Total Iron Concentration and Iron Speciation on the Rate of Ferrous Iron Oxidation Kinetics of Leptospirillum ferriphilum in Continuous Tank Systems
Authors: Petersen Jochen , Ojumu Tunde Victor
Published: March 2009

In this study the results from a systematic study of the oxidation kinetics of
Leptospirillum ferriphilum in continuous culture at total iron concentrations ranging from 2 to12
g/L are reported. In all experiments the steady-state concentrations of ferrous iron were small and
comparable, and at least 97% of was as ferric. Surprisingly, the specific ferrous iron utilisation rate
decreased with increasing total iron concentration, while yield coefficients increased. It was noted
that the biomass concentration in the reactor (as measured by both CO2 uptake rate and cell counts)
dramatically increased with increasing total iron concentrations, whereas it stayed more or less the
same over a wide range of dilution rates at a given total iron concentration. The experimental data
was re-analysed in terms of ferrous iron kinetics using Monod kinetics with a ferric inhibition term.
The results confirm that the maximum specific iron utilisation rate is itself a function of ferric iron
concentration, declining with increasing concentration. It thus appears that high concentrations of
ferric iron stimulate microbial growth while at the same time inhibiting the rate of ferrous iron
oxidation. It is postulated that these phenomena are related, i.e. that more growth occurs to reduce
the load on the individual cell, possibly by sharing some metabolic functions.
Isolation, Characterization and Phylogenetic Analysis of Acidiphilium-Like Bacteria from Acid Mine Drainage
Authors: Zhang Yan Fei , Yang Yu , Liu Jian She , Qiu Guan Zhou
Published: March 2009

The acidophilic heterotrophic bacteria Acidiphilium spp. were considered as a ministrant
of Leptospirillum spp., Acidithiobacillus spp. and other autotrophic bacteria in acid mine drainage
(AMD). 25 Acidiphilium-like bacterial strains were isolated from eight different mines in China and
their physiology was characterized. Their marmatite-bioleaching ability has been investigated and
compared with that of a mixed culture of Acidiphilium sp. and Acidithiobacillus ferrooxidans. The
results indicated that some Acidiphilium-like strains exhibited a high marmatite-bioleaching ability,
which was even higher than that of Acidithiobacillus ferrooxidans. The leaching efficiency was not
higher in mixed than in pure culture. The phylogenetic relationship of the 25 Acidiphilium-like
strains was analyzed by 16S rRNA sequencing, GyrB sequencing and rep-PCR genomic
fingerprinting. The 25 strains and other eight species of Acidiphilium spp. were clustered into three
groups.
Development of an Extremophilic Iron Oxidizing Consortium and a Fixed Film Bioreactor for Generation of Ferric Lixivient
Authors: Dave Shailesh R. , Shah T.J. , Tipre D.R.
Published: March 2009

Acidophilic iron-oxidizing microorganisms are important for both, the environment and for biotechnological applications. Biogeneration of ferric from ferrous iron was studied using an iron-oxidizing consortium developed during polymetallic concentrate bioleaching. A promising iron oxidizing consortium was developed by adaptation and selection, which resulted in bacterial iron oxidation activity under the extreme conditions of 250 g/L ferrous sulphate as initial substrate and 500 g/L ferric sulphate. The development of iron oxidizers improved the iron oxidation rate from 0.019 to as high as 0.6 g/L/h in the shake flask studies with 25 % initial ferrous sulphate in the medium. The consortium showed dominance of Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans. A fixed film bioreactor was further developed to improve rates of iron oxidation. The developed fixed film bioreactor operated successfully for 200 batches without external addition of inoculum with the highest iron oxidation rate of 1.89 g/L/h. The biological ferric iron generation process provides continuous leaching agent in the form of ferric sulphate, which would be a promising eco-friendly biotechnological process for the indirect extraction of precious metals from sulphidic mineral concentrates.
Enrichment of Chromium-Reducing Bacteria Using Potential-Controlled Electrochemical Cultivation
Authors: Matsumoto Norio , Hirano Shinichi , Ohmura Naoya
Published: March 2009

We present here a method for the electrochemical enrichment of chromium-reducing
bacteria from environmental samples containing various microorganisms. An electrochemical
cultivation system was constructed; this consisted of a Pt anode and a carbon cathode separated by
an ion-exchange membrane. For an electrochemical cultivation, an environmental sample with
chromium-reducing bacteria was inoculated into the anode well where a medium containing 0.1
mM Cr(VI) ions was poured. On the other hand, Cr(VI)-free medium was poured into the cathode
well. Chromium-reducing bacteria grew selectively after 10 days of incubation and application of
1.0 V (vs. Ag/AgCl) of anode potential that reproduces Cr(VI) ions. This result suggested that
Cr(VI) ions generated on the anode promoted the growth of chromium-reducing bacteria as their
electron acceptor and due to Cr(VI) toxicity, inhibited the growth of other microorganisms.
High-Level Resistance to Cobalt and Nickel in Cuban Serratia marcescens Strains Isolated from Serpentine Deposits
Authors: Marrero Jeannette , Auling Georg , Coto Orquidea , Nies Dietrich
Published: March 2009

A collection of highly nickel and cobalt-resistant enterobacteria were isolated from the Punta Gorda serpentine deposit (Moa, Cuba). The most nickel and cobalt resistant strain (termed C- 1) was assigned to Serratia marcescens by 16S rRNA analysis and DNA/DNA hybridization and the molecular mechanisms underlying its inducible cobalt and nickel resistance was investigated. Genes involved in metal resistance were identified by transposon mutagenesis followed by selection for Co- and Ni-sensitive derivatives. The transposon insertion causing the highest decrease in metal resistance was located in the ncrABC determinant. The three ORFs (ncrA, ncrB and ncrC) were cloned in E. coli. The predicted NcrA product was an NreB ortholog of the major facilitator protein superfamily and was central for Co/Ni resistance in S. marcescens strain C-1. NcrA also mediated metal resistance in E. coli and caused decreased accumulation of Co and Ni in this heterologous host. NcrB may be a regulatory protein. NcrC was a protein of the Ni–Co transport (NiCoT) protein family and necessary for full metal resistance in E. coli, but only when NcrA was also present. Without NcrA, NcrC caused a slight decrease in metal resistance and mediated increased accumulation of Ni and Co. As the cytoplasmic metal concentration can be assumed to be the result of a flow equilibrium of uptake and efflux processes, this interplay between metal uptake system NcrC and metal efflux system NcrA may contribute to nickel and cobalt resistance in this bacterium.
Iron Homeostasis Strategies in Acidophilic Iron Oxidizers: Comparative Genomic Analyses
Authors: Quatrini Raquel , Martínez Verónica , Osorio Hector , Veloso Felipe A. , Pedroso Inti , Valdés Jorge H. , Jedlicki Eugenia , Holmes David S.
Published: March 2009

An understanding of the physiology and metabolic complexity of microbial consortia involved in metal solubilization is a prerequisite for the rational improvement of bioleaching technologies. Among the most challenging aspects that remain to be addressed is how aerobic acidophiles, especially Fe(II)-oxidizers, contend with the paradoxical hazards of iron overload and iron deficiency, each with deleterious consequences for growth. Homeostatic mechanisms regulating the acquisition, utilization/oxidation, storage and intracellular mobilization of cellular iron are deemed to be critical for fitness and survival of bioleaching microbes. In an attempt to contribute to the comprehensive understanding of the biology and ecology of the microbial communities in bioleaching econiches, we have used comparative genomics and other bioinformatic tools to reconstruct the iron management strategies in newly sequenced acidithiobacilli and other biomining genomes available in public databases. Species-specific genes have been identified with distinctive functional roles in iron management as well as genes shared by several species in biomining consortia. Their analysis contributes to our understanding of the general survival strategies in acidic and iron loaded environments and suggests functions for genes with currently unknown functions that might reveal novel aspects of iron response in acidophiles. Comprehensive examination of the occurrence and conservation of regulatory functions and regulatory sites also allowed the prediction of the metal regulatory networks for these biomining microbes.
Monitoring of Microbial Community Inhabiting a Low-Grade Copper Sulphide Ore by Quantitative Real-Time PCR Analysis of 16S rRNA Genes
Authors: Remonsellez Francisco , Galleguillos F. , Janse van Rensburg Sonestie , Rautenbach G.F. , Galleguillos Pedro A. , Castillo Danny , Demergasso Cecilia
Published: March 2009

Microbial heap bioleaching is being used as an industrial process to recover copper from
low grade ores. It is known that a consortium of different microorganisms participates in this
process. Therefore identification and quantification of communities inhabiting heap bioleaching
operations is a key step for understanding the dynamics and role of these microorganisms in the
process. A quantitative real-time PCR approach was used to investigate the microbial dynamics in
this process. To study the microbial population inhabiting a low-grade copper sulphide ore
bioleaching industrial heap process at Escondida Mine in Chile, 16S rRNA genetic libraries were
constructed using bacterial and archaeal universal primers. Phylogenetic analyses of sequences
retrieved from genetic libraries showed that the community is mainly composed by microoganisms
related to Acidithiobacillus ferrooxidans (2 strains), Acidithiobacillus thiooxidans, Leptospirillum
ferrooxidans, Leptospirillum ferriphilum and the archaea Ferroplasma.
Specific primers for real-time PCR determination were designed and tested to amplify each of
the sequences obtained by cloning. Standard curves for real time PCR were performed using
plasmid DNA from selected clones. This methodology is actually being used to monitor relevant
microorganisms inhabiting this low-grade copper sulphide ore bioleaching industrial heap.
Analysis of the Microbial Community in an Acid Ground Water Characterized by Sulfate Reduction Activity
Authors: Gumnior Kristin , Hoth Nils , Schlömann Michael , Seifert Jana
Published: March 2009

Open pit mining characterizes the area of Lusatia (Germany), which corresponds to
dramatic changes of the natural ecosystem. Landscapes with huge waste heaps and acid mine
lakes are created by former mining activities.
The studied waste heap is about 70 years old and is situated between two lakes (Restsee
107 and Restsee 108) formed ten years later. Samples taken by drilling drills showed hints of
active sulfate reduction activities within the heap and the ground water. Black precipitations
were visible on the sediment cores and an intensive H2S odor was noticed.
Investigations of the hydrochemistry of the ground water within the heap were started with
the drilling of twelve wells along two parallel lines (I, II). Various analytical parameters were
measured (see Storch et al. IBS 2007, short lecture topic environmental problems).
The bacterial communities of two wells are investigated by molecular methods. The water
samples differ in pH (MPL1: 2.4 and MPL11: 4.4) and were therefore chosen to investigate
into more detail. Creating a 16S rDNA library, the microbial diversity in the water was
characterized. The 200 clones of sample MPL11 were highly diverse: a restriction analysis
using the enzyme RsaI revealed 120 different restriction types. Numbers of sequences were
related to sulfate reducing bacteria and to uncultivated bacteria from acidic environmental
sites. The obtained sequences will be used to study the remaining wells by T-RFLP and to
discuss these results in respect to sulfate reduction under acidic conditions.
Lead and Gold Removal Using Sugar-Beet Pectin Gels with and without Immobilized Fucus Vesiculosus
Authors: Mata Yasmina N. , Torres Elena , Blázquez M. Luisa , Ballester Antonio , González F. , Muñoz J.A.
Published: March 2009

Sugar-beet pectin gels are a novel material with applications in heavy and precious metal removal and biomass immobilization which are similar to those of alginate. This paper presents the experimental results of the kinetics of Pb(II) and Au(III) batch removal with these gels, with and without immobilized biomass of the brown algae Fucus vesiculosus. The evolution of the metal concentration, solution pH and Ca2+ liberation was determined. The biomass was characterized before and after the metal removal using SEM-EDX, FESEM, FETEM, XRD and FTIR techniques. The Pb(II) removal followed a typical biosorption kinetics with a final equilibrium metal concentration. The immobilized algae had different biosorptive behaviour than both the original sugar-beet pectin gels and the free biomass. There was no Au(III) removal with the pectin gels without algae. In the case of the immobilized biomass, the Au(III) recovery occurred in two stages, where the biosorption was followed by the reduction of the Au(III) to Au(0) due to the presence of the own algae. The Au(0) precipitated preferably on the surface of the algal biomass and in the form of colloidal gold in the solution and entrapped within the pectin gel matrix.
The Role of Carotenoid Pigments in Cr(VI) Tolerance, Biosorption and Bioaccumulation by Rhodotorula mucilaginosa UCM Y-1776 and its Mutants
Authors: Mameeva Olag G. , Kasatkina T.P. , Podgorsky V.S.
Published: March 2009

To compare Cr (VI) tolerance, biosorption and bioaccumulation for initial carotenoidsproducing
yeast Rhodotorula mucilaginosa UCM Y-1776 and its mutants, twenty stable mutants
with various intensity of colors were obtained using nitrosoguanidine (NSG). The ultraviolet was
found to be inefficient as a mutagen in our study. Light- and non-pigmented mutants (4L and 2)
demonstrated a significant growth inhibition by 30 mg/l Cr (VI) whereas wild strain was able to
grow at much higher chromium concentrations (500 mg/l). Cr (VI) sorption ability of R.
mucilaginosa UCM Y-1776 was higher than those of mutants. Cr (VI) sorption/uptake parameters
(Qmax, b) were found to be close for initial pink-pigmented R. mucilaginosa UCM Y-1776 (Qmax
= 950 5M/g), and its light-pigmented mutant 4L (Qmax = 678 5M/g) and non-pigmented mutant 2
(Qmax = 790 5M/g) by non-living biomass. Non-pigmented “white” mutant 2 showed the highest
ability to sorb chromium ions by living biomass (Qmax = 1020 mmol/g). The least chromiumtolerant
light-pigmented (mutant 4L) and non-pigmented yeasts showed the highest chromium
uptake for living biomass.
The results showed that the presence of carotenoids did not affect Cr (VI) ions sorption by yeast
biomass which could highlight significance of chitin and glucan-mannoprotein complex in
chromium biosorption. However pigment absence increased Cr (VI) bioaccumulation by living
yeast demonstrating the protective role of carotenoids against hexavalent chromium toxicity.
Sorption of Copper Ions by Biogenic Iron Sulphides
Authors: Luptakova Alena , Macingova E.
Published: March 2009

Biogenic iron sulphides are excellent adsorbents for various heavy metals ions.
Consequently, they have practical application for the elimination of heavy metals from waste
waters. One of the principles for the iron sulphides preparation is the application of sulphatereducing
bacteria. This biological-chemical method is based on the ability of these bacteria to
reduce sulphates to hydrogen sulphide, which binds with the ferrous cations to form insoluble
precipitates – iron sulphides. Under certain bacterial growth conditions biogenic iron sulphides can
be magnetic.
The aim of this work is to study the possibility of using SRB for the preparation of iron sulphides,
which were used subsequently in the framework of sorption tests to eliminate copper ions from
model solutions.
Characterization of Cellulosic Biomass Loaded with Iron and Arsenic Using High Energy X-Rays
Authors: Cordeiro Silva G. , Pinto de Carvalho Regina , Dantas M. Sylvia S. , Ciminelli Virgínia S.T.
Published: March 2009

The biosorption of arsenic species by dried lettuce leaves (L.sativa) was investigated.
Arsenic sorption, that is not effective on in natura biomass, was enhanced when the biomass was
previously loaded with Fe(III). Analysis of X-ray Absorption Near-Edge Spectroscopy (XANES)
spectra showed that iron was incorporated as Fe(III) and arsenic as As(V), regardless the contact
with the lowest or highest valence species of these elements. The features of Extended X-ray
Absorption Fine-Structure Spectroscopy (EXAFS) spectra suggest that the nearest neighboring
atoms of iron ions are the same in all the samples, even in the As-Fe loaded ones. These results
indicate the arsenic oxyanions as the sorbed species on the iron-loaded biomass.