bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative AE Techniques Standardized for Concrete Structures
Authors: Ohtsu Masayasu
Published: March 2009

Acoustic emission (AE) techniques have been extensively applied to concrete structures.
Up-dated results are currently standardized to inspect and evaluate the structures in service.
Consequently, test results based on these standards are reviewed and discussed.
In order to assess the damage levels of the structures, the recommended practice is proposed by
the Japanese Society for Non-Destructive Inspection. Two AE parameters of load ratio and calm ratio
are defined for qualification of the damages. It is reported that damages qualified are in good
agreement with actual damages of reinforced concrete members under bending.
AE behavior of concrete under compression could be analyzed, applying the rate process analysis.
By quantifying intact Young’s moduli of concrete from the database, relative damages of concrete in
existing structures are successfully estimated.
The committee on nondestructive inspection of steel-reinforced concrete structures in the
Federation of Construction Materials Industries, Japan, has recently published new standards on
estimation of concrete properties by elastic-wave methods. One of them is a monitoring method for
active cracks in concrete by AE, which is applied to study corrosion cracking in concrete.
Moment tensor analysis of AE can identify cracking kinematics of location, crack-type and crack
orientation, which is implemented as SiGMA procedure. Nucleation of micro-cracking due to
corrosion is identified. It is found that the mechanisms iof corrosion cracking in concrete are nearly
equally of mode I, mixed-mode and mode II.
Acoustic Emission Testing of Concrete Frame during Pseudo Dynamic Loading
Authors: Anastasopoulus Athanasios , Bousias S. , Tsimogiannis A. , Toutountzakis T.
Published: March 2009

Acoustic Emission (AE) monitoring was performed during Pseudo-Dynamic Testing of a
torsionally unbalanced, two-storey, one-by-one bay reinforced concrete frame structure. The
structure represented a 0.7-scale model of a real-size frame structure designed and detailed
according to the standards prevailing in Greece in 60's, without engineered earthquake resistance.
Real time monitoring of AE activity versus the complex applied load resulted in semi quantitative
damage characterization as well as comparative evaluation of the damage evolution of the different
size columns. Evolution of the AE energy rate per channel, as revealed from zonal location, and the
energy rate of linearly located sources enabled the identification of damage areas and the forecast of
crack locations before cracks were visible with naked eye. In addition to that, the results of post
processing evaluation allowed for the verification of the witnessed damaged areas and formed the
basis for quantitative assessment of damage criticality.
Acoustic Emission Parameters Dependence on the Destruction Process Characteristics into Concrete
Authors: Elizarov Sergey V. , Alyakritsky A.L. , Sagaidak A.I.
Published: March 2009

Acoustic emission (AE) techniques are extensively applied to a variety of fields
including civil engineering. Now a new generation of AE techniques, which are able to register and
process AE data in real-time, has appeared. Still, there exist some problems to correctly interpreting
these data and to completely understand the meaning of AE parameters. In order to solve this,
several AE waveform and spectral parameters are investigated, based on an experimental study of
concrete and reinforced concrete structures.
Application of Acoustic Emission for Monitoring the HVOF Thermal Spraying Process
Authors: Faisal Nadimul Haque , Steel John A. , Ahmed Rehan , Reuben R.L. , Heaton G. , Allcock Bryan
Published: March 2009

This research aims to characterise and quantify the acoustic emission (AE) generated
during the high velocity oxy-fuel (HVOF) thermal spraying process, recorded using piezoelectric
AE sensors. The HVOF process is very complex involving high temperature turbulent flow through
a nozzle with entrained particles, the projection of these particles, and their interaction with the
target surface. Process parameters such as gun speed, oxy-fuel pressure and powder specification
affect various characteristics of the coating, including thermal residual stresses; the lamellar
microstructure and the topology and geometry of pores, all formed when the fused powder hits the
surface, forming “splats”. It is widely acknowledged in the thermal spray industry that existing
quality control techniques and testing techniques need to be improved. New techniques which help
to understand the effects of coating process parameters on the characteristics of the coating are
therefore of value, and it was anticipated that recording the AE produced when the fused particles
contact the surface would aid this understanding. As a first stage, we demonstrated here that AE
associated with particle impact can, in fact, be discerned in the face of the considerable airborne and
structure-borne noise.
In order to do this, a new test method using a masking sheet with slits of varying size was
developed. Thermal spraying was carried out for a range of spray gun speeds and process
parameters. The AE was measured using a broad band AE sensor positioned on the back of the
sample as the spot was traversed across it. The results show that the amplitude and energy of the
AE signals is related to the spray gun speed, powder used and the oxy-fuel pressure. Using a simple
geometrical model for particle impact, the measured AE was found to vary with the energy and
number of particles impacting on the sample in a predictable way.
AE Monitoring of CFRP Structure during Autoclave Processing
Authors: Knuuttila Markku
Published: March 2009

Large structural composite sandwich panels (approx. 2x4 m2) were found to have cracks
in the honeycomb core. The core was made out of a number of Nomex honeycomb blocks having
different densities. These were first machined and adhesively bonded into the final shape. The
CFRP skins were then added and the sandwich panel was cured in an autoclave applying elevated
temperature and pressure.
Acoustic emission monitoring was done during 17 hours of processing in the autoclave using a six
channel AE system. AE events from cracking of the honeycomb core were registered and could be
identified in time and space. The results from AE monitoring were very useful for modifying the
process parameters and overcome the cracking of the core.
Experimental Validation of Dispersion Curves in Plates for Acoustic Emission
Authors: Pullin Rhys , Theobald Pete T. , Holford Karen M. , Evans S.L.
Published: March 2009

This paper presents the findings of an investigation to determine theoretically and
empirically the wave speeds and frequency content of the two primary Lamb wave modes, the
symmetric (S0) and anti-symmetric (A0). A 2 mm thick steel plate measuring 700 mm by 700 mm
was used to perform all measurements. A broadband pulse propagated through the plate and
detected by a conical type piezoelectric receiver was used to show how the dispersive properties of
the plate influenced the detected AE signals. It was shown that the two primary Lamb wave modes
cover a very broad range of velocities, leading to a severe spreading of arrival times.
A further investigation was completed using four acoustic emission sensors to record a pencil
lead fracture, which was used as an artificial source. Reflections in the plate were shown to cause
interference in the signal that can complicate the interpretation of the arrival modes. A recorded
signal 400mm from the source was filtered into frequency bands. The arrival times of the wave
modes were determined for each frequency band and the appropriate velocities calculated allowing
a dispersion curve to be plotted experimentally. The plotted curve was shown to be a very close
approximate to the calculated curve.
Contrasts between the Acoustic Emission Signals Generated by Monopole Versus Dipole Sources
Authors: Hamstad Marvin A.
Published: March 2009

Acoustic emission (AE) practitioners routinely use surface pencil lead breaks
(monopoles) to observe expected AE signal characteristics. In contrast, stress-generated AE sources
are almost universally composed of dipoles. Thus, understanding the primary differences between
the signals generated by these two different source classes is of key importance. This research had
the goal of analyzing and contrasting the AE signals generated by monopole and dipole sources. A
finite-element-modeled database of AE signals provided an ideal means to study these two source
types. The AE signals represented the top-surface out-of-plane displacement versus time from point
sources inside an aluminum plate 4.7 mm thick. In addition, monopole sources both on the plate top
surface and the edge surface were included in the database. The AE signals were obtained from both
in-plane and out-of-plane monopole and dipole sources. Results were analyzed with both a 100 to
300 kHz bandpass filter and a 40 kHz high-pass filter. The wide-plate specimen domain effectively
eliminated edge reflections from interfering with the direct signal arrivals.
Acoustic Emission Detection Using a Novel Fibre Optic Sensor
Authors: Chen Rong Sheng , Burns J.M. , Bradshaw Timothy P. , Cole P.T. , Jarman P. , Theobald R. , Pedder D. , Fernando G.F.
Published: March 2009

A novel fibre optic sensor system has been developed for detection of acoustic emission.
The sensor design was based on a 2×2 fused tapered optical fibre coupler configuration. Given the
intended use of this sensor for the detection of acoustic emission in smart materials and structures,
its lightweight, compatibility with composite material and immunity from electromagnetic
interference are great advantages. Apart from the performance specification and reliability, the
overall cost of the sensor system is a major factor in their adoption by end-users. The manufacturing
of this sensor is low-cost and the signal output from the sensor system developed can be directly fed
to the commercial AE acquisition system. The demonstration of acoustic emission detection was
conducted using fibre coupler-based AE sensors in different materials and structures. The AE
sources are various and depend on the different applications. In the current paper, we report on the
use of the fibre optic AE sensor system for concrete damage monitoring. An experiment on damage
detection on a composite plate with this fibre optical AE sensor is also reported in the paper.
Degradation Behaviour of Metallic Biomaterials for Degradable Stents
Authors: Hermawan Hendra , Moravej Maryam , Dubé Dominique , Fiset Michel , Mantovani Diego
Published: March 2009

The short-term need of scaffolding function of stent and the prevention of potential longterm
complication of permanently implanted stent have directed to the original idea of
biodegradable stent. Selecting and developing materials showing appropriate mechanical and
degradation properties are key steps for the development of this new class of medical devices.
Therefore, the study of their in vitro degradation behaviour is mandatory for the selection of
potential candidate materials suited in vivo.
In this work, the degradation behaviour of current studied biodegradable metals including three
magnesium alloys (Mg, AM60B and AZ91D), pure iron and Fe-35Mn was investigated. The tests
were performed in a simulated blood plasma solution at 37±0.1 oC, using three different methods;
potentiodynamic polarization, static immersion, and dynamic test in a test-bench which mimics the
flow condition in human coronary artery. Degradation rate was determined as ion release rate
measured by using atomic adsorption spectroscopy (AAS) and also estimated from weight loss and
corrosion current. Surface morphology and chemical composition of corroded specimens were
analyzed by using SEM/EDS.
The three degradation methods provide consistent results in corrosion tendency, where Mg
showed the highest corrosion rate followed by AZ91D, AM60B, Fe-35Mn and iron.
Potentiodynamic polarization gives a rapid estimation of corrosion behaviour and rate. Static
immersion test shows the effect of time on the degradation rate and behaviour. Dynamic test
provides the closest approach to the environment after stent implantation and its results show the
effect of the flow on the materials degradation. In conclusion, the three investigated methods can be
applied for screening, selecting and validating materials for degradable stent application before
going further to in vivo assessments.
Research on Water Based Coating for Magnesium Alloy
Authors: Huang Wei , Li Di , Zheng Tian Liang
Published: March 2009

Magnesium and its alloys have many applications for theirs excellent physical and
mechanical properties. Due to magnesium’s active chemical properties and difficulties in direct
painting, a novel environmental protective water based coating was developed, which mainly
contains metal flake, silicate, silane and sodium polyphosphate etc. The properties and structure of
the coating were investigated by adhesion test, hardness test, heat resistance test, neutral salt spray
test and Scanning Electron Microscopy (SEM) et al. Meanwhile, the effect of sodium polyphosphate
was also examined by hydrogen evolution test and electrochemical test. Furthermore, the film
forming mechanism of the coating was explored by Fourier Transform Infrared spectroscopy (FTIR).
Results showed that the coating had a stepped structure which could achieve extraordinary adhesion,
350°C temperature heat resistance, HV0.50/30 210 hardness and 300 hours anti-corrosion time in salt
spray test. In the coating, the addition of sodium polyphosphate could greatly improve the corrosion
resistance of the coating because of the barrier film formed by sodium polyphosphate. The
mechanism of interpenetrating polymer network (IPN) was preliminary put forward based on the
results of FTIR.
Improvement of the Mechanical Properties of High Manganese Steels by Combination of Precipitation Hardening and Mechanical Twinning
Authors: Iker Mathieu , Gaude-Fugarolas Daniel , Jacques Pascal J. , Delannay Francis
Published: March 2009

Twinning-Induced Plasticity steels (TWIP steels) are extensively studied due to their
ultra-high strain-hardening rate, that brings about a remarkable combination of ductility and
strength. Twinning can be observed in high manganese-carbon steels. This paper considers
hardening by combination of mechanical twinning with carbide precipitation. The kinetics of
precipitation and the morphological evolution of carbides with annealing time were studied for two
different TWIP steels with high manganese and carbon contents. The steels are first cold-rolled and
then annealed at 800°C for recrystallization and carbide precipitation. Depending on the steel
composition, the kinetics of precipitation and the morphology of the carbides are quite different.
The influence of the annealing cycle on the mechanical properties has also been assessed. The
results are used to discuss the influence of composition, stacking fault energy (SFE) and carbide
precipitation on twinning. We show that the usual criteria based on the SFE only are not sufficient
to characterize the twinning ability of a steel.
Application of Mesophilic Mixed Micro-Organisms for Recovery of Valuable Metals from Spent Refinery Catalysts
Authors: Kim Dong Jin , Mishra D. , Ralph D.E. , Ahn Jong Gwan , Rhee Y.H.
Published: March 2009

Bioleaching of pre-treated spent refinery catalyst was performed using sulfur and iron
oxidizing bacteria separately. Both the mixed cultures were grown at various concentration of either
ferrous sulfate or elemental sulfur. Bioleaching process was conducted by varying the reaction time,
effect of substrates and effect of catalyst amount. Under the most favourable transport conditions
examined, (5g/L spent catalysts, 10g/L ferrous sulfate, reaction time 7 days) the mixed iron
oxidizing bacteria were able to recover Ni, V, and Mo of 90, 80 and 54 % respectively. Higher
catalyst and ferrous sulfate concentration showed decline result in recovery of Mo and V. Ni
showed consistent results throughout the series of experiments (88 to 90% recovery).
The mixed sulfur oxidizing bacteria were observed to be more effective than the iron oxidizing
bacteria. The sulfur oxidizing cells were able to recover Ni, V and Mo of 88, 94 and 46 %
respectively (spent catalysts 50g/L, elemental sulfur of 2% (w/v), reaction time 7 days). The
oxidation of elemental sulfur to sulfate could play a vital role for extraction of the metals.
The Effect of Aluminium and Magnesium Sulphate on the Rate of Ferrous Iron Oxidation by Leptospirillum ferriphilum in Continuous Culture
Authors: Ojumu Tunde Victor , Petersen Jochen , Hansford Geoffrey S.
Published: March 2009

In heap bioleaching the dissolution of gangue minerals from igneous ore materials can
lead to the build-up of considerable concentrations of Mg and Al sulphates in the recycled leach
solution. This may interfere with microbial ferrous iron oxidation, which drives the oxidation of the
target minerals. The kinetics of the oxidation process have been well studied for Leptospirillum and
Acidithiobacillus species in tank systems. Although not directly comparable, kinetic parameters
derived for tank systems do apply also for heap bioleach conditions. In the present study the effect
of solution concentrations of Mg and Al as sulphate at individual concentrations of 0 to 10 g/L and
combined concentrations 0 to 16 g/L each has been investigated in continuous culture using
Leptospirillum ferriphilum. Increasing the concentrations of the salts increasingly depresses the rate
of ferrous iron oxidation and also shifts the viable range more and more into the low potential
region. Al significantly reduces the amount of carbon maintained in the reactor (assumed to be
commensurate with biomass), whereas Mg actually enhances it at low concentrations. In both cases,
however, the rate is always depressed. The results indicate that heap cultures are likely to perform
sub-optimally in those operations where build-up of dissolved gangue minerals is not controlled.
Modelling of Contaminant Release from Mining Waste Deposits
Authors: Moreno L.
Published: March 2009

The release of contaminants from mining wastes containing sulphide minerals is
addressed. The paper shows the application of a methodology, Performance Assessment (PA), to
the long-term behaviour of waste deposits. The aim of the paper is to address the different processes
that occur in deposits for mining waste. These processes are applied to one study case; drainage
water from a waste rock dump at the Aitik mine in northern Sweden.
Treatment of Uranium-Containing Drainage Water in a Pilot-Scale Plant by Means of Microbial Reduction
Authors: Glombitza F. , Kutschke S. , Kiessig G. , Zellmer A.
Published: March 2009

Water draining a waste dump at the Hartenstein site of the former uranium mining
company SDAG Wismut is characterised by an uranium concentration between 1mg/L and 3 mg/L
and a nitrate concentration from 30 mg/L to 120 mg/L. A microbiological process was developed
between 2001 - 2003 under laboratory conditions and, after this time, the process was scaled up to a
technical plant. The water was treated continuously by a controlled microbiological process under
anaerobic conditions with methanol as the sole carbon and energy source. The reduction plant is a
basin filled with about 540 m³ of gravel and with a free water volume of about 200 m³. The plant
was foreseen for the treatment of a drainage water flow rate of 2 m³/h – 5 m³/h. The residence time
of the treated water in the plant comprises 40 h– 100 h according to the water flow. The continuous
process started in 2004. The Uranium concentration decreased to values lower than 0.5 mg/L. The
arsenic concentration varied in a range from 60 to 80 .g/L after reaching stable anaerobic
conditions. The plant worked also during deep temperatures in the wintertime.
Microbial and Geochemical Characterization of an Acid-Generating Hard Coal Tailings Dump in Saxonia/ Germany
Authors: Willscher Sabine , Starke Sophie , Katzschner M. , Felix Manfred
Published: March 2009

An enhanced entry of heavy metals and metalloids into ground and surface water was
observed in the historical hard coal mining areas of the districts of Zwickau and Lugau/ Oelsnitz in
Saxonia, Germany. Heavy metals and metalloids like Mn, Co, Ni, Zn, As and Cd are enriched in the
surface waters of the district. This environmental impact is observed even though a recultivation of
some of the dumps occurred partially already 50 years ago. In this study, preliminary microbial and
geochemical characterizations of samples from drilling cores in different depths of a dump site, of
surface and ground water samples, and of sediments are described. Thiobacillus denitrificans
appeared to be a dominating species in these moderately acidic environment especially where there
is nitrate infiltration and inflow, respectively, due to agricultural use of the adjacent area. Some of
the sediment samples also contained high counts of iron- and sulfate-reducing bacteria due to the
organic detritus on the sediment surface.
A Study of the Operating Parameters of a Sulphate-Reducing Fixed-Bed Reactor for the Treatment of Metal-Bearing Wastewater
Authors: Kousi Pavlina , Remoudaki E. , Hatzikioseyian Artin , Tsezos Marios
Published: March 2009

An upflow fixed-bed sulphate-reducing reactor has been set up and monitored for the treatment of metal-bearing wastewater. Zinc has been chosen as the target metal to be sequestered from influent water stream at initial concentrations ranging from 50 to 400 mg/l and initial pH values ranging from 3 to 5. Main operating parameters of the reactor, such as the composition and content of electron donor, electron acceptor, sulphate and metal removal capacity, have been monitored during ten months of continuous operation. The results obtained have shown that the reactor has a considerable capacity of completely reducing sulphates for initial concentrations up to 7,200 mg/l, completely removing soluble zinc for initial concentrations up to 400 mg/l and completely removing Total Organic Carbon (TOC), for initial concentrations up to 1,500 mg/l.
Sustainable Approach for the Immobilization of Metals in the Saturated Zone: In Situ Bioprecipitation
Authors: Vanbroekhoven Karolien , Van Roy Sandra , Diels Ludo , Gemoets Johan , Verkaeren Paul , Zeuwts Ludo , Feyaerts Karel , van den Broeck Francis
Published: March 2009

In order to remediate three sites in the vicinity of a non-ferrous industrial site, where
groundwater was historically contaminated with metals, the best available technique should be
selected. Because the groundwater contained high concentrations of metals and high sulphate
concentrations (up to 2000 ppm), the feasibility of sulphate reduction and subsequent metal
immobilization due to metal sulphide precipitation was examined in the lab before selecting an
appropriate remediation technology. Because of the very high metal concentrations in the
groundwater and their potential toxic effects on microbial life chemical reagents were also
evaluated for immobilization of the metals in situ.
The first site (site 1) was characterized by a contamination of Zn (500ppm-3ppm) up to a depth
of 130 m-bg. A screening for inducibility of biological activity was performed at two depths – 30
m-bg (below ground) and 65 m-bg -- using microcosm experiments containing both aquifer solids
and groundwater. Different electron-donors were selected including pure chemical agents such as
lactate and waste products such as molasses and glycerol. Glycerol resulted in the most efficient
metal and sulphate removal after about 106 days.
Extremely high Zn concentrations were found in the groundwater of the second site (site 2), i.e.,
up to about 2000 ppm. Similar lab tests applied for site 1 were performed, but in addition chemical
agents (NaS2 and CaSx) were used. Whereas the sulphide containing chemical agents immediately
resulted in low Zn concentrations in the groundwater, it took >140 days before biological sulphate
removal started. Glycerol, lactate and molasses resulted in efficient Zn removal.
Site 3 was characterized by relative shallow contamination (<10 m-bg) of mainly Co (30-300
ppm), and containing typical sulphate concentrations in the range of 300-1200 ppm. Rapid
microbial sulphate reduction (within 50 days) was induced in the tests containing nutrient-amended
lactate, cheese whey and soy oil.
Regulation of PCE-Dechlorinating Activity by Electrochemical Cultivation
Authors: Hirano Shinichi , Matsumoto Norio , Ohmura Naoya
Published: March 2009

Tetrachloroethene (PCE) is one of the grave environmental pollutants. Certain anaerobic
bacteria have the ability to dechlorinate PCE as an electron acceptor for their respiration
(dehalorespiration). Previously, we accumulated PCE-dechlorinating culture in the presence of
Fe(III)-EDTA. In this study, we have described the regulation of dehalorespiration by electrolytic
control of the Fe(II)/Fe(III) ratio using a potentiostat (electrochemical cultivation).
PCE-dechlorinating culture was cultivated under H2 conditions at constant redox potentials ranging
from –0.1 to –0.8 V. After electrochemical cultivation for 3 weeks, PCE-dechlorinating activity of
the mixed culture varied at different redox potentials. At –0.6 V, the culture showed the highest
activity and the highest ratio of Desulfitobacterium/total bacteria. Electrochemical cultivation is a
useful method for regulating PCE-dechlorinating bacterium.
Hydrolysed Cellulose Material as Sulfate Reduction Electron Donor to Treat Metal- and Sulfate Containing Waste Water
Authors: Lakaniemi Aino Maija , Nevatalo Laura M. , Kaksonen Anna H. , Puhakka Jaakko A.
Published: March 2009

The amenability of hydrolysed cellulose material to low cost sulfate reduction electron
donor was examined with fluidized bed reactor (FBR) treating synthetic mine waste water. The
studied cellulose material was dried Phalaris arundinacea reed, which was acid hydrolysed (1.5
w/w % H2SO4, 7 w/w % solids) at 120oC to hydrolyse polymeric materials to biodegradable
monomers. The FBR was operated at 35oC, and ethanol has previously been used as the electron
donor. FBR was fed with synthetic waste water (pH 4.5) containing soluble fraction of Phalaris
arundinacea hydrolysate, metals (Fe and Zn) and sulfate.
The switch of the electron donor from ethanol to hydrolysate was successful. The acidic influent
was neutralized in the FBR by the alkalinity produced in the oxidation of Phalaris arundinacea
hydrolysate. The main oxidation product of the soluble hydrolysate was acetate, which accumulated
in the FBR during overloading. The percent sulfate reduction remained in the range of 40-95 %.
The highest obtained hydrogen sulfide production was 0.91 g L-1d-1 at a hydraulic retention time
(HRT) of 9 h, while highest sulfate reduction was 8.4 g L-1d-1 (HRT 8 h). Iron and zinc precipitated
in the FBR, and highest metal precipitation rates were 1.14 g Fe L-1 d-1 and 30 mg Zn L-1d-1 (HRT 8
h). The electron donor load was measured as soluble chemical oxygen demand (CODs), and highest
CODs removal rate was 2.13 g L-1d-1 (HRT 9 h) and CODs percent oxidation 92 % (HRT 10 h).
Soluble Phalaris arundinacea hydrolysate was found to be a suitable electron donor for sulfate
reducing FBR and mine waste water treatment. The soluble fraction of Phalaris arundinacea
hydrolysate was used very efficiently by sulfate-reducing bacteria (SRB). Additionally, batch bottle
assays showed that SRB-enrichment also used solid, dried Phalaris arundinacea as electron donor
for sulfate reduction (total sulfide yield 340 mg L-1 in 14 days). The results of sulfate reduction and
iron precipitation are shown in figures 1 A-B.
Pyrite Surface Alteration of Synthetic Single Crystals as Effect of Microbial Activity and Crystallographic Orientation
Authors: Etzel Katja , Huber Harald , Rachel Reinhard , Schmalz Gottfried , Thomm Michael , Depmeier Wulf
Published: March 2009

To enhance our understanding of effects of microbially mediated pyrite dissolution and the
influence parameters such as varied metabolism and crystallographic orientation of pyrite surfaces
some dissolution experiments were performed. Microbial etching experiments on pyrite surfaces of
different orientation, including {111} and {210} were devised. The experiments were performed
using two strains of thermophilic Archaea (Sulfolobus metallicus, Metallosphaera sedula).
Epifluorescence microscopy observations showed that the strains attach to the mineral surface.
Studies with Scanning Electron Microscopy (SEM) showed cell attachment and etching effects after
one week of incubation. Surface alteration produced structures following crystallographic
orientation up to several 10 μm in size. For all incubated pyrite samples it became apparent that
surface alteration was more pronounced with M. sedula than with S. metallicus.
Surface Hydrophobicity of an Acidophilic Heterotrophic Bacterium of Mine Origin under Metal Stress
Authors: Pakshirajan K.
Published: March 2009

Cell surface hydropobicity plays a significant role in microbe-mineral interactions with special relevance of bioleaching. The present investigation envisages a study on the hydrophobic character of Acidiphilium symbioticum KM2, an acidophilic strain of bioleaching environment, when grown in presence of heavy metals - copper, zinc, cadmium and nickel. The metals, at its sub inhibitory concentrations (MIC50), exhibited profound negative effect on the growth of the bacterium. Inhibition on the culture growth rate was highest due to cadmium followed by zinc, nickel and copper. However, upon successive adaptation in different concentrations of each metal in ascending order, the cells could grow rapidly in the presence of higher concentrations of the metals indicating good metal resistance by the bacterium. Compared to normally grown cells, A. symbioticum KM2, when grown in presence of the metals, became more hydrophobic, which was dependent on the metal and its concentration in the media. Among the four metals studied, the effect of copper was found to be the highest, where up to 74 % increase in the bacterial cell hydrophobicity was observed.
Selective Coagulation in Chalcopyrite/Pyrite Mineral System Using Acidithiobacillus Group Bacteria
Authors: Vilinska Annamaria , Hanumantha Rao K. , Forssberg K.S.Eric
Published: March 2009

Acidithiobacillus ferrooxidans cells grown in ferrous ions were used to study the surface modification of pyrite and chalcopyrite, with focus on coagulation of very fine particles (-5 m). The zeta-potential studies of the minerals, before and after bacterial treatment, showed that the cells have a distinct influence on the surface charge of pyrite and chalcopyrite. The maximum coagulation of particles determined by Turbiscan as a function of pH correlated well with the zetapotential results. Using diffuse reflectance FT-IR spectroscopic studies, the adhesion of cells showed a varied influence on these minerals. The results demonstrate that Acidithiobacillus ferrooxidans interact with pyrite and chalcopyrite differently, allowing selective coagulation of one mineral from the other under different pH conditions.
Combined Atomic Force and Fluorescence Microscopy of Biofilms formed by Leaching Bacteria on Opaque Substrata
Authors: Mangold Stefanie , Harneit Kerstin , Sand Wolfgang
Published: March 2009

Leaching bacteria attach to their substrates, i.e. mineral sulfides, and form monolayered
biofilms. In this study the biofilm formation of Acidithiobacillus ferrooxidans A2 on pyrite was
examined using atomic force and epifluorescence microscopy (AFM and EFM, respectively). A
novel system by JPK instruments, the BioMaterial WorkstationTM, allows the investigation of the
same location on an opaque sample with AFM and EFM. Until recently this was only possible for
translucent samples. Sessile bacteria on pyrite coupons were stained with 4’,6-diamidino-2-
phenylindol (DAPI) and visualized by EFM as well as AFM. The best imaging conditions for AFM
were assessed. Scans of bacteria attached to pyrite were performed in contact mode in air as well as
in tapping mode in fluid. Imaging in fluid was more challenging than imaging in air as bacteria tend
to detach from their substratum. To avoid the dislocation of microorganisms by the AFM probe the
sample was dried in air for 1 h prior to scanning in fluid. Scanning in air was performed with the
whole range of cantilever spring constants tested (k = 0.03 N/m to k = 0.65 N/m) while, for
scanning in fluid, best results were achieved using stiffer cantilevers (k = 0.65 N/m).
Geographical Distribution and Diversity of Moderately Thermophilic Members of the Thermoplasmatales
Authors: Hawkes Rebecca , O'Hara Graham , Franzmann Peter D. , Plumb Jason J.
Published: March 2009

Oxidation of ferrous iron by moderately thermophilic species of the genus Ferroplasma is of considerable potential value in commercial bioleaching operations. A collection of strains was enriched and isolated from a number of natural or industrial acidic sites at 45 and 55°C. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that all strains were members of the Order Thermoplasmatales. Stains BH8 and BH12 showed 98% sequence similarity with Ferroplasma acidiphilum strain YT and DR1 respectively. Strains BH7 and BH10 were closely related to the moderately thermophilic species Ferroplasma cupricumulans. Strain BH9, a moderately thermophilic organotroph, was unrelated to previously described species and probably represents a novel genus. Strains BH8 and BH12 showed some unique physiological differences to the type species F. acidiphilum. Unlike F. acidiphilum, both strains were moderately thermophilic with a temperature range for strains BH8 and BH12 of 24 to 61°C and 27 to 49°C respectively. Strain BH12 grew organotrophically on Darland’s Medium containing glucose and yeast extract and chemomixotrophically on Darland’s Medium supplemented with ferrous sulphate. Moderately thermophilic species of Ferroplasma and Ferroplasma-like genera appear widely distributed geographically and possess considerable physiological and phylogenetic diversity that may benefit industrial bioleaching processes.
Molecular Assessment of Microbial Diversity and Community Structure at Uranium Mines of Jaduguda, India
Authors: Sar Pinaki , Dhal Paltu K. , Islam Ekramul , Kazy Sufia K.
Published: March 2009

Microbial diversity associated with uranium mine areas of Jaduguda, India has been
investigated using a culture independent molecular approach. Soil samples collected from existing
and proposed mine sites were analyzed for physicochemical parameters. Community DNA was
extracted from five samples. Small subunit rRNA gene (16S rRNA) was PCR amplified using
bacterial primers. The diversity of the total bacterial community was described at molecular level
by amplified ribosomal DNA restriction analysis (ARDRA). Dominant bacterial groups (represents
by OTUs) selected by ARDRA were identified by sequencing the 16S rRNA genes. From the
bacterial rDNA clone library around 230 clones were used for further analysis. The unique OTUs
and number of clones representing such OTUs were determined. Dominant OTUs were sequenced
and identified. These phylotypes spanned a wide range within the bacterial domain occupying
Proteobacteria, Acidobacteria, Bacteroidetes, Firmicutes, Cyanobacteria as major phyla. About 46
% of clones sequenced from various sites were identified as Proteobacteria. The present findings on
microbial diversity at the molecular level are the first of its kind for uranium mine sites of India.
Around 20 % of the clone sequences showed little affiliation with known taxa and probably
represent new organisms adapted to this habitat.
Interactions of Acidithiobacillus ferrooxidans with Heavy Metals, Various Forms of Arsenic and Pyrite
Authors: Dave Shailesh R. , Gupta K.H.
Published: March 2009

An arsenic resistant ferrous iron oxidizing bacterium Acidithiobacillus ferrooxidans
(GenBank no. EF010878) was isolated from reactor leachate. The reactor leachate showed extreme
environmental parameters. Ferrous iron concentrations of more than 60 g/L were found to be
inhibitory in the presence and absence of arsenite. Ks values of 12.5 and 8.0 g/L ferrous sulphate
and Vmax of 0.124 and 0.117 g/L/h/0.8 mg of protein were found in the presence and absence of
arsenite respectively. At 14.9 g/L of arsenite and arsenate the culture showed 26.8 and 59.7 %
ferrous iron oxidizing activity respectively. Amongst the metals studied, copper was found to be
more toxic as compared to nickel and zinc. In the presence of 3.51 g/L nickel or 4.68 g/L zinc,
about 30 % biooxidation activity was registered. In the pyrite oxidation study 87, 67 and 64 % of
pyrite oxidation was found and 2.02, 3.19 and 5.96 g/L total iron was solubilized with 5, 10 and 20
g/L of pyrite respectively. The isolate was also able to oxidize refractory arsenopyrite gold ore and
0.531 g/L of arsenic was solubilized along with 0.872 g/L of soluble total iron. During this period
the numbers of planktonic bacteria increased from 2.4 x 106 to 1.0 x 108 cells/mL.
Ferrous Iron Oxidation by Salt-Tolerant “Thiobacillus prosperus”
Authors: Davis-Belmar Carol S. , Nicolle James Le C. , Norris Paul R.
Published: March 2009

Growth on ferrous iron of a new isolate of the halotolerant acidophile “Thiobacillus prosperus” occurred with a substrate oxidation rate similar to that of Acidithiobacillus ferrooxidans, but with a requirement for salt (NaCl). These observations contrast with the previous description of “T. prosperus” in which a salt requirement was not noted and growth on ferrous iron was described as poor. As well as similar capacities for iron oxidation, these species were shown to possess similar clusters of genes (the rus operon) that encode proteins likely to be involved in transfer of electrons from ferrous iron. There were some differences in the organization of the genes and one of them that encodes a cytochrome c in At. ferrooxidans was absent from the “T. prosperus” cluster.
Insights into the Metabolism and Ecophysiology of Three Acidithiobacilli by Comparative Genome Analysis
Authors: Valdés Jorge H. , Pedroso Inti , Quatrini Raquel , Hallberg Kevin B. , Valenzuela Pablo D.T. , Holmes David S.
Published: March 2009

Draft genome sequences of Acidithiobacillus thiooxidans ATCC 19377 and A. caldus
ATCC 51756 have been annotated. Bioinformatic analysis of these two new genomes, together with
that of A. ferrooxidans ATCC 23270, allows the prediction of metabolic and regulatory models for
each species and has provided a unique opportunity to undertake comparative genomic studies of
this group of bioleaching bacteria. In this paper, we report preliminary information on metabolic
and electron transfer pathways for ten characteristics of the three acidithiobacilli: CO2 fixation, the
TCA cycle, sulfur oxidation, sulfur reduction, iron oxidation, iron assimilation, hydrogen oxidation,
flagella formation, Che signaling (chemotaxis) and nitrogen fixation. Predicted transcriptional and
metabolic interplay between pathways pinpoints potential coordinated responses to environmental
signals such as energy source, oxygen and nutrient limitations. The predicted pathway for nitrogen
fixation in A. ferrooxidans will be described as an example of such an integrated response. Several
responses appear to be especially characteristic of autotrophic microorganisms and may have direct
implications for metabolic processes of critical relevance to the understanding of how these
microorganisms survive and proliferate in extreme environments, including industrial bioleaching
operations.
Identification, Some Characterizations and Bioleaching Application of an Iron-Oxidizing Bacterium, Acidithiobacillus ferrooxidans KLipis-3-1 Isolated from Malaysia
Authors: Yee Sei Choong , Lim Choon Ping , Ng Kim Yong
Published: March 2009

A strain of At. ferrooxidans was isolated from Penjom Goldmine, Kuala Lipis, Pahang, Malaysia. The 16S rRNA partial gene sequence analysis revealed that this rod-shaped bacterium with size of 0.3 x 0.8 -m is a strain of At. ferrooxidans, and was designated as At. ferrooxidans KLipis-3-1. The whole-cell FAMEs profile analysis showed that At. ferrooxidans KLipis-3-1 possesses large amounts of C18:1, C16:0 and C16:1 fatty acids with C18:1 as the predominant fatty acid. The initial specific iron-oxidizing and molybdenum blue-oxidizing activities of this bacterium were 88.85 mMh-1mg-1 and 196.86 mMh-1mg-1, respectively, which were similar to the activities observed in the type strain At. ferrooxidans ATCC 23270. However, At. ferrooxidans KLipis-3-1 has a higher resistance towards Mo6+ at concentration above 1 mM. At. ferrooxidans KLipis-3-1 has the ability to reduce ferric ion with elemental sulfur as electron donor, with the initial specific SFORase activity of 0.47 mMh-1mg-1. The bioleaching capability of At. ferrooxidans KLipis-3-1 and At. ferrooxidans ATCC 23270 with pyrite as substrate at selected parameters operated in a batch bioprocess were studied.
Temperature Effects on the Iron Oxidation Kinetics of a Leptospirillum ferriphilum Dominated Culture at pH Below One
Authors: Özkaya Bestamin , Nurmi Pauliina , Sahinkaya Erkan , Kaksonen Anna H. , Puhakka Jaakko A.
Published: March 2009

In this study, ferrous iron oxidation rates of a Leptospirillum ferriphilum dominated culture were determined over the temperature range of 2-50oC at pH below one. The results show that at pH 0.9 the culture oxidizes iron within the temperature range of 10°C to 45°C. Using the Arrhenius equation, an Ea value of 89.9 ± 6.75 kJ/mol was calculated. From the data fitted to Ratkowsky Equation, the optimum, minimum and maximum temperatures were 35 ± 1.5, 9.96 ± 1.72 and 42.93 ± 0.64 °C for this culture, respectively. The redox potential of the solution becomes more positive, which was the maximum (650-700 mV) at temperatures between 19-40 oC due to completing biological oxidation and increasing in ferric iron concentration.
Metabolism Peculiarities of Bacteria of the Genus Sulfobacillus
Authors: Zhuravleva Anna E. , Tsaplina I.A. , Ismailov A.D. , Zakharchuk L.M. , Karavaiko G.I.
Published: March 2009

The genus Sulfobacillus includes moderately thermophilic and thermotolerant acidophilic
bacteria, which prefer mixotrophic growth conditions. These organisms are S. thermosulfidooxidans
1269Т, S. sibiricus N1Т and S. thermotolerans Kr1Т. The simultaneous presence of organic (for
example yeast extract) and inorganic energy sources is essential for optimal growth. Carbon sources
are both CO2 and organic compounds. During their mixotrophic growth, the basic pathways of
carbohydrate catabolism of sulfobacilli are those of glycolysis, oxidative pentose phosphate and
Entner–Doudorov (excepting strain N1). Assimilation of CO2 is carried out both auto- and
heterotrophically. Final stages of oxidation of organic substances serve for cell biosynthesis.
Bacteria are able to switch to organo- and autotrophic metabolism. At that the enzyme activities of
pentose phosphate pathway are not detected. The cycle of tricarboxylic acids is disrupted at the
level of 2-oxoglutarate dehydrogenase. The glyoxylate bypass is absent. The maximal protein and
ATP values and high intensity of respiration in S. thermosulfidooxidans, S. sibiricus and S.
thermotolerans cultures were determined under mixotrophic conditions. Studied strains due to their
flexible carbon and energetic metabolism together with other microorganisms of communities
(leptospirilli and archaea) participate in sulfide minerals processing at 40-450C without organic
compounds supplement.
Quantification of Microorganisms Involved in Cemented Layer Formation in Sulfidic Mine Waste Tailings (Freiberg, Saxony, Germany)
Authors: Kock Dagmar , Graupner Torsten , Rammlmair Dieter , Schippers Axel
Published: March 2009

Cemented layers predominantly consisting of gels/poorly crystalline mineral phases have been formed as a consequence of mineral weathering in sulfidic tailings near Freiberg, Saxony, Germany. These layers function as natural attenuation barrier for toxic compounds and reduce oxidation and erosion processes of tailings surfaces. Quantitative molecular biological and cultivation methods were applied to investigate the role of microorganisms for mineral weathering and cemented layer formation. High resolution depth profiles of numbers of microorganisms showed maximal cell numbers in the oxidation zone where cemented layers had been formed. Highest total cell numbers of >109 cells g-1 dry weight (dw) were detected by SybrGreen direct counting. Using quantitative real-time PCR (Q-PCR) between 107 and 109 Bacteria g-1 dw and up to 108 Archaea g-1 dw were determined. As well high numbers of cultivable and living Bacteria could be detected by MPN (most probable number) for Fe(II)- and S-oxidizers and CARD-FISH (catalyzed reporter deposition - fluorescence in situ hybridization). Overall, the high numbers of microorganisms determined with various quantification techniques argue for a significant role of microorganisms in cemented layer formation due to microbial mineral weathering. It is hypothesized that EPS (extracellular polymeric substances) mediate the formation of secondary mineral phases.
The Diversity of Benthic Microorganisms in Acidic Mine Lake Sediments
Authors: Pham Huynh A. , Oldham Carolyn E. , Plumb Jason J.
Published: March 2009

The sediment microbial communities of a disused coal mine lake, Lake Kepwari (pH~4.5-5) were studied to understand how the natural microbial processes in an oligotrophic acidic mine lake system influence the iron and sulphur cycles. Most probable number (MPN) viable counts were used to enumerate the benthic bacteria at different depths. MPN results revealed an abundance of bacteria that were capable of growing in sulphate reducing medium with numbers in the range of 1 × 107 – 1 × 108 cells.g-1 of wet sediment. In contrast, MPN results showed much lower numbers of bacteria that were capable of growing in ferric reducing medium with 1 × 102 – 2 × 103 cells.g-1 of wet sediment detected. Serial decimal dilution cultures were used to isolate pure strains of benthic bacteria. Strains HP1, HP2 and HP3 were isolated from benthic lake sediments at 18 m, 0 m and 10 m water depths respectively. 16S rRNA gene sequence analysis of strain HP1 showed that the strain belonged to the genus Enterobacter, strain HP2 belonged to the Order Rhizobiales and strain HP3 belonged to the sub-order Micrococcineae. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments was used to profile the diversity of the benthic microbial communities at different depths. DGGE profiling of benthic sediments revealed that sediments contained mostly members of the Proteobacteria, Actinobacteria and Firmicutes phyla.
Research on isc Operon in Acidithiobacillus ferrooxidans ATCC 23270
Authors: Liu Jian She , Zhang Yan Fei , Geng Mei Mei , Zeng Jia , Qiu Guan Zhou
Published: March 2009

The highly conserved operon iron–sulfur cluster (iscSUA) is essential for the general
biogenesis and transfer of iron–sulfur proteins in bacteria. In this study, expression, purification and
characterization of the proteins of the isc operon (iscSUA) of Acidithiobacillus ferrooxidans ATCC
23270 was studied. Assembly and transfer of [Fe4S4] in vitro during the isc proteins and other iron
sulfur proteins was studied in order to detect the pathway and mechanism of [Fe4S4] assembly and
transfer in vivo. The [Fe4S4] cluster was successfully assembled in iron-sulfur proteins in vitro in the
presence of Fe2+ and sulfide, and it was successfully transferred from IscA or IscU to iron- sulfur
proteins. Our results support and extend certain models of iron-sulfur clusters assembly and
transfer.