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Acid production of fungi isolated from stones of historical monuments in the state of minas gerais, Brazil
Abstracts
responsible for the observed fluctuations in filter element life. The retention of organic substances, particularly proteins and lipids, was also found to contribute to a reduction in filter element life, particularly during the spring, summer and autumn, coinciding with the seasonal increases in the numbers of planktonic organisms in seawater.
Environmental Fate of Sacrificial Zinc Anodes and Influence of a Biotllm P. Wagner”, B. Little”, K. Hart”, R. Raya, D. Thorna. and P. Tnaskoma-Pauletteb “Naval Research Laboratory, Stennis Space Center, MS and bNaval Research Laboratory, Washington, DC, USA
Laboratory experiments were performed to determine the environmental fate of zinc compounds formed during sacrificial dissolution of zinc anodes in seawater and to determine the role of biofllms in mobilizing/immobilizing zinc corrosion products. Experimental conditions simulated cathodic protection and overprotection of shop ballast tanks. Anodic dissolution and percentage of soluble zinc increased with the level of protection. For normal cathodic protection in abiotic seawater, approximately 3% of the sacrificed zinc was dissolved in solution. Additionally, weight loss and percent soluble products increased dramatically in the presence of an agar film, but were unchanged with natural marine biofilms. Under overprotection conditions, weight loss was determined by protection current and did not vary in the presence of surface films. Solid zinc corrosion products were precipitated, suspended in solution, and attached to electrode surfaces. Experimental data were compared with zinc concentrations measured in ballast tanks for two US Navy surface ships.
Electrochemical Behavior of AI 7075 in Mixed Cultures of Hormoconis resinae
125
corrosion processes. The elemental material composition as well as the environmental conditions determine the extent of deterioration. The aim of this study is to determine the influence of concentration of selenium, nickel and iron on the growth and activity of SRB. As a model microorganism we have chosen DesulJbvibrio desulfuricans, New Jersey, a member of the SRB group and hence an important corrosioninducing species. Experiments were carried out in batch and continuous reactors with pH and temperature control. Kinetics of sulfate reduction and production of metabolic products for the different concentrations is evaluated.
Kinetic and Mechanistic Studies of SRB Influenced Corrosion: a First Approach V.L. Rainha”, A.R. Linob, M.J. Feiob and I.T.E. Fonsecan “CECUL, Detartamento Quimica, Universidade de Lisboa, Portugal and Institute de Tecnologia Quimica e Biologica, Oeiras, Portugal
The influence of the sulfate reducing bacteria (SRB) Desulfovibrio desuljiiricans ATCC 27774, grown in a lactate/sulfate medium, on the anaerobic corrosion of mild steel was evaluated. Potentiostatic transients and potentiodynamic polarizations (both unidirectional and cyclic) were performed, both in pure cultures and in the sterile medium. Potentiostatic transient analysis revealed typical parameters of “inverse” nucleation in the transpassive region for the sterile media and ionic exchange and diffusion for the inoculated media. Cyclic voltammetry results pointed to the same conclusions. Tafel analysis allowed us to verify that SRB presence induces modifications in the kinetics and in the mechanism of the anodic dissolution of iron, even permitting the exclusion of some of the possible mechanisms. The rate determining step is probably a chemical step in the inoculated media, whereas it is an electrochemical step in the sterile media. Proposal of a final mechanism requires, however, complementary studies, with a rigorous control of some variables.
A.M. Palermo, S. Cldcldzola, D. Baleani and B.M. Rosales CEICOR, CITEFA-CONICET,
Argentina
The alloy Al 7075 was electrochemically analysed in mixed cultures of Hormoconis resinae derived from strains that had lost their corrosive capacity. In one of these cultures a decrease in the pitting potential (E,) of about 1500 mV was found after an incubation of 45 days. In this case, a delay in the lag phase with respect to the original corrosive strains was also observed. After 30 days of incubation no differences in Ep were detected with respect to the sterile controls, while in the original corrosive strains the lag phase was 3-5 days. Scanning electron microscopy was used to determine the morphology of the attack nucleated at the respective Ep, verifying the recovery of the corrosiveness by the mixed culture.
Influence of Micronutrient Concentration on Growth and Activity of Sulfate Reducing Bacteria C.V. Pluto”, R. PereiraO,M.J.T. Carrondo”-band M.A.M. Reis” aDepartment of Chemistry, New University of Lisbon, Monte de Caparica, Portugal and bI.T.Q.B./I.B.E.T., Oeiras, Portugal
Microorganisms can significantly influence a variety of environmental and economical processes. The role of anerobic sulfate reducing bacteria (SRB) in corrosion of iron and ferrous alloys is well documented. Many industrial sectors suffer great economic losses and experience health and safety hazards as a result of SRB activitieis. SRB produce metabolic products such as volatile fatty acids and H$ which improve
Acid Production of Fungi Isolated from Stones of Historical Monuments in the State of Minas Gerais, Brazil M.A. Resende, G.C. Resende, E.M. Viana, T.W. Becker and T. Warscheid I.C.B. Federal University of Minas Gerais, Belo Horizonte, Brazil and I.C.B.M., University of Oldenburg. Germany
The release of corrosive acids belongs to the most well-known and most investigated biogeochemical destructive mechanism on the surface of rocks. This process, known as biocorrosion, results from the biogenic release of organic and inorganic acids. Samples of quartzite and soapstone were taken from the sanctuary of Born Jesus de Matosinhos in Congonhas, SLo Francisco de Assis Church, in Ouro Preto and Nossa Senhora Mae dos Homens Church in Caraca. The historical monuments were chosen under various expositional aspects. Sample material was powdered and suspended in sterile 0.001% Tween 80 solution before inoculation in the media. The fungi were identified by observing the morphology of the colony and the micromorphology in slide culture. The acid production was observed by cultivation of the fungi in Czapek-Dox broth for 14 days at 28°C and the pH of the cultures was measured with a pHmeter. Among the major acid producers are: Verticillium lecanii, Penicillium expansum, Penicillium nigricans, Aspergilius japonicus, Aspergillus ochraceus, Aspergillus puniceus, Mucor hiemalis and Fusarium oxysporum. The acids are
being identified by HPLC.
responsible for the observed fluctuations in filter element life. The retention of organic substances, particularly proteins and lipids, was also found to contribute to a reduction in filter element life, particularly during the spring, summer and autumn, coinciding with the seasonal increases in the numbers of planktonic organisms in seawater.
Environmental Fate of Sacrificial Zinc Anodes and Influence of a Biotllm P. Wagner”, B. Little”, K. Hart”, R. Raya, D. Thorna. and P. Tnaskoma-Pauletteb “Naval Research Laboratory, Stennis Space Center, MS and bNaval Research Laboratory, Washington, DC, USA
Laboratory experiments were performed to determine the environmental fate of zinc compounds formed during sacrificial dissolution of zinc anodes in seawater and to determine the role of biofllms in mobilizing/immobilizing zinc corrosion products. Experimental conditions simulated cathodic protection and overprotection of shop ballast tanks. Anodic dissolution and percentage of soluble zinc increased with the level of protection. For normal cathodic protection in abiotic seawater, approximately 3% of the sacrificed zinc was dissolved in solution. Additionally, weight loss and percent soluble products increased dramatically in the presence of an agar film, but were unchanged with natural marine biofilms. Under overprotection conditions, weight loss was determined by protection current and did not vary in the presence of surface films. Solid zinc corrosion products were precipitated, suspended in solution, and attached to electrode surfaces. Experimental data were compared with zinc concentrations measured in ballast tanks for two US Navy surface ships.
Electrochemical Behavior of AI 7075 in Mixed Cultures of Hormoconis resinae
125
corrosion processes. The elemental material composition as well as the environmental conditions determine the extent of deterioration. The aim of this study is to determine the influence of concentration of selenium, nickel and iron on the growth and activity of SRB. As a model microorganism we have chosen DesulJbvibrio desulfuricans, New Jersey, a member of the SRB group and hence an important corrosioninducing species. Experiments were carried out in batch and continuous reactors with pH and temperature control. Kinetics of sulfate reduction and production of metabolic products for the different concentrations is evaluated.
Kinetic and Mechanistic Studies of SRB Influenced Corrosion: a First Approach V.L. Rainha”, A.R. Linob, M.J. Feiob and I.T.E. Fonsecan “CECUL, Detartamento Quimica, Universidade de Lisboa, Portugal and Institute de Tecnologia Quimica e Biologica, Oeiras, Portugal
The influence of the sulfate reducing bacteria (SRB) Desulfovibrio desuljiiricans ATCC 27774, grown in a lactate/sulfate medium, on the anaerobic corrosion of mild steel was evaluated. Potentiostatic transients and potentiodynamic polarizations (both unidirectional and cyclic) were performed, both in pure cultures and in the sterile medium. Potentiostatic transient analysis revealed typical parameters of “inverse” nucleation in the transpassive region for the sterile media and ionic exchange and diffusion for the inoculated media. Cyclic voltammetry results pointed to the same conclusions. Tafel analysis allowed us to verify that SRB presence induces modifications in the kinetics and in the mechanism of the anodic dissolution of iron, even permitting the exclusion of some of the possible mechanisms. The rate determining step is probably a chemical step in the inoculated media, whereas it is an electrochemical step in the sterile media. Proposal of a final mechanism requires, however, complementary studies, with a rigorous control of some variables.
A.M. Palermo, S. Cldcldzola, D. Baleani and B.M. Rosales CEICOR, CITEFA-CONICET,
Argentina
The alloy Al 7075 was electrochemically analysed in mixed cultures of Hormoconis resinae derived from strains that had lost their corrosive capacity. In one of these cultures a decrease in the pitting potential (E,) of about 1500 mV was found after an incubation of 45 days. In this case, a delay in the lag phase with respect to the original corrosive strains was also observed. After 30 days of incubation no differences in Ep were detected with respect to the sterile controls, while in the original corrosive strains the lag phase was 3-5 days. Scanning electron microscopy was used to determine the morphology of the attack nucleated at the respective Ep, verifying the recovery of the corrosiveness by the mixed culture.
Influence of Micronutrient Concentration on Growth and Activity of Sulfate Reducing Bacteria C.V. Pluto”, R. PereiraO,M.J.T. Carrondo”-band M.A.M. Reis” aDepartment of Chemistry, New University of Lisbon, Monte de Caparica, Portugal and bI.T.Q.B./I.B.E.T., Oeiras, Portugal
Microorganisms can significantly influence a variety of environmental and economical processes. The role of anerobic sulfate reducing bacteria (SRB) in corrosion of iron and ferrous alloys is well documented. Many industrial sectors suffer great economic losses and experience health and safety hazards as a result of SRB activitieis. SRB produce metabolic products such as volatile fatty acids and H$ which improve
Acid Production of Fungi Isolated from Stones of Historical Monuments in the State of Minas Gerais, Brazil M.A. Resende, G.C. Resende, E.M. Viana, T.W. Becker and T. Warscheid I.C.B. Federal University of Minas Gerais, Belo Horizonte, Brazil and I.C.B.M., University of Oldenburg. Germany
The release of corrosive acids belongs to the most well-known and most investigated biogeochemical destructive mechanism on the surface of rocks. This process, known as biocorrosion, results from the biogenic release of organic and inorganic acids. Samples of quartzite and soapstone were taken from the sanctuary of Born Jesus de Matosinhos in Congonhas, SLo Francisco de Assis Church, in Ouro Preto and Nossa Senhora Mae dos Homens Church in Caraca. The historical monuments were chosen under various expositional aspects. Sample material was powdered and suspended in sterile 0.001% Tween 80 solution before inoculation in the media. The fungi were identified by observing the morphology of the colony and the micromorphology in slide culture. The acid production was observed by cultivation of the fungi in Czapek-Dox broth for 14 days at 28°C and the pH of the cultures was measured with a pHmeter. Among the major acid producers are: Verticillium lecanii, Penicillium expansum, Penicillium nigricans, Aspergilius japonicus, Aspergillus ochraceus, Aspergillus puniceus, Mucor hiemalis and Fusarium oxysporum. The acids are
being identified by HPLC.