Juan Pablo Busalmen | Universidad Nacional de Mar del Plata (original) (raw)

Papers by Juan Pablo Busalmen

Langmuir, 2007

The interaction between bacterial cells of Pseudomonas fluorescens (ATCC 17552) and gold electrod... more The interaction between bacterial cells of Pseudomonas fluorescens (ATCC 17552) and gold electrodes was analyzed by cyclic voltammetry (CV) and attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). The voltammetric evaluation of cell adsorption showed a decrease in the double-layer capacitance of polyoriented single-crystal gold electrodes with cell adhesion. As followed by IR spectroscopy in the ATR configuration, the adsorption of bacterial cells onto thin-film gold electrodes was mainly indicated by the increase in intensity with time of amide I and amide II protein-related bands at 1664 and 1549 cm -1 , respectively. Bands at 1448 and 2900 cm -1 corresponding to the scissoring and the stretching bands of CH 2 were also detected, together with a minor peak at 1407 cm -1 due to the V s COOstretching. Weak signals at 1237 cm -1 were due to amide III, and a broad band between 1100 and 1200 cm -1 indicated the presence of alcohol groups. Bacteria were found to displace water molecules and anions coadsorbed on the surface in order to interact with the electrode intimately. This fact was evidenced in the SEIRAS spectra by the negative features appearing at 3450 and 3575 cm -1 , corresponding to interfacial water directly interacting with the electrode and water associated with chloride ions adsorbed on the electrode, respectively. Experiments in deuterated water confirmed these assignments and allowed a better estimation of amide absorption bands. In CV experiments, an oxidation process was observed at potentials higher than 0.4 V that was dependent on the exposure time of electrodes in concentrated bacterial suspensions. Adsorbed bacterial cells were found to get closer to the gold surface during oxidation, as indicated by the concomitant increment in the main IR bacterial signals including amide I, a sharp band at 1240 cm -1 , and a broad one at 1120 cm -1 related to phosphate groups in the bacterial membranes. It is proposed to be due to the oxidation of lipopolysaccharides on the outermost bacterial surface.

Polymer Degradation and Stability, 2004

... The composites and the unfilled matrix showed hydrolytic stability at pH 7.2 at two different... more ... The composites and the unfilled matrix showed hydrolytic stability at pH 7.2 at two different temperatures (25 °C and 40 °C). Fibres were stable under hydrolytic conditions and seemed to favour the entrance of water and then, the swelling and the hydrolysis of the starch (the ...

Environmental Science & Technology, 2008

The mechanism(s) by which electricity-producing microorganisms interact with an electrode is poor... more The mechanism(s) by which electricity-producing microorganisms interact with an electrode is poorly understood. Outer membrane cytochromes and conductive pili are being considered as possible players, but the available information does not concur to a consensus mechanism yet. In this work we demonstrate that Geobacter sulfurreducens cells are able to change the way in which they exchange electrons with an electrode as a response to changes in the applied electrode potential. After several hours of polarization at 0.1 V Ag/AgClsKCl (saturated), the voltammetric signature of the attached cells showed a single redox pair with a formal redox potential of about -0.08 V as calculated from chronopotentiometric analysis. A similar signal was obtained from cells adapted to 0.4 V. However, new redox couples were detected after conditioning at 0.6 V. A large oxidation process beyond 0.5 V transferring a higher current than that obtained at 0.1 V was found to be associated with two reduction waves at 0.23 and 0.50 V. The apparent equilibrium potential of these new processes was estimated to be at about 0.48 V from programmed current potentiometric results. Importantly, when polarization was lowered again to 0.1 V for 18 additional hours, the signals obtained at 0.6 V were found to greatly diminish in amplitude, whereas those previously found at the lower conditioning potential were recovered. Results clearly show the reversibility of cell adaptation to the electrode potential and point to the polarization potential as a key variable to optimize energy production from an electricity producing population.

Bioelectrochemistry, 2010

In this work we report on the occurrence of at least two different redox pairs on the cell surfac... more In this work we report on the occurrence of at least two different redox pairs on the cell surface of the electrogenic bacteria Geobacter sulfurreducens adsorbed on gold that are expressed in response to the polarization potential. As previously reported on graphite (Environ. Sci. Technol. 42 (2008) 2445) a typical low potential redox pair is found centered at around − 0.06 V when cells are polarized for a few hours at 0.2 V, while a new pair centered at around 0.38 V is expressed upon polarization at 0.6 V. Reversible changes in the IR band pattern of whole cells where obtained by Attenuated Total Reflection-Surface Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) upon potential cycling around both redox pairs. Changes clearly resemble the electrochemical turnover of oxidized/reduced states in c-type cytochromes, thus evidencing the nature of the involved molecules. The expression of external cytochromes in response to the potential of the electron acceptor suggests the existence of alternative pathways of electron transport with different energy yield, though it remains to be demonstrated.

Electrochimica Acta

Electroactive bacterial biofilms can be produced on a polarized electrode by forcing its use as t... more Electroactive bacterial biofilms can be produced on a polarized electrode by forcing its use as the final electron acceptor for bacterial respiration. This strategy offers the researcher the unique possibility to control the respiration process with extreme precision. The production of current, the accumulation of charge and the conducting properties of electroactive biofilms has been interrogated in this work through very basic electrochemical techniques including chronopotentiometry, chronoamperometry and cyclic voltammetry. Presented results indicate that charge can be accumulated in the biofilm conductive network, that network conductivity does not represent a limit for current production and that both the steady state current and the amount of accumulated charge depend on the redox state of cytochromes wiring the cells to the electrode. A model of biofilm conduction is presented as well.

Environmental Science & Technology, 2006

Laboratory-scale experiments were performed in which the corrosion protection of stainless steels... more Laboratory-scale experiments were performed in which the corrosion protection of stainless steels in seawater was afforded by cathodic protection. The method was implemented for the first time using the potential difference at the marine sediment/seawater interface as the only source of electric power. Graphite electrodes buried in marine sediment, developing a potential of -0.45 V versus a saturated calomel electrode (SCE), were used as anodes to cathodically polarize UNS S30403 stainless steel coupons that were exposed to seawater. The cathodic protection system was operated with low polarization of stainless steel, typically to -0.2 V (vs SCE) and was found to properly prevent material failure even in the presence of a well-developed biofilm. With voltammetry, the protection current was found to be related to the oxidation of reduced sulfur compounds in the sediments. Results demonstrate that this inexpensive and environmentally friendly method can, so far, extend the service life of stainless steels in seawater.

Journal of Industrial Microbiology & Biotechnology, 2001

The adherence of an environmental strain of Pseudomonas sp. to titanium was evaluated modifying t... more The adherence of an environmental strain of Pseudomonas sp. to titanium was evaluated modifying the pH (2 to 8) and ionic strength (0.1 and 0.6 M NaCl) of the electrolyte solution. Results were analyzed considering the participation of the different interfacial forces under the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. At 0.1 M, maximal bacterial adhesion was at pH 6, in agreement with the point of zero charge of the titanium surface. Similar adhesion values were observed at both sides of this point despite the opposite electrostatic condition of the surface oxide. At 0.6 M an absence of bacterial adhesion was observed throughout the pH range tested. The changes in bacterial adhesion are in agreement with the changes in the number of reinforced H-bond-forming sites on the titanium surface calculated using a simple model for the ionization of OH group adsorbed to the surface. Journal of Industrial Microbiology & Biotechnology (2001) 26, 303–308.

Electrochimica Acta, 2002

Changes on the oxygen reduction rate induced on aluminium brass by cell-free bacterial cultures o... more Changes on the oxygen reduction rate induced on aluminium brass by cell-free bacterial cultures of an isolate belonging to the genus Pseudomonas were studied in relation to the bacteria phase of growth and to the surface oxide layer composition after various electrochemical pre-treatments of the metal samples. Cultures isolated from the stationary phase of growth strongly influenced the oxygen reduction kinetics. Cathodic currents increased throughout the potential range tested when Cu 2 O and CuO were present simultaneously in the surface film (so-called aged surfaces). In this case, the maximum increment (35%) was observed within the oxygen reduction limiting current region. On pre-oxidised surfaces, when the oxide film was composed mainly by CuO, the effect induced by stationary phase cultures was even higher, with the limiting current density increasing by almost 60%. On pre-reduced surfaces on the other hand, when only a submonolayer of Cu 2 O was covering the surface, there was no effect as current density values were similar to those obtained in control experiments. Exponential phase cell-free cultures did not modify the limiting current values in any of the surfaces investigated. Results were in agreement with the participation of catalase as a bacterial catalyst for the oxygen reduction process. The normalised catalase activity from different stationary phase cell-free cultures ranged from 0.88 to 4.02 mg ml − 1 U − 1 , while there was no observable activity in exponential phase cultures. The incidence of the catalase mechanism in microbiologically influenced corrosion processes induced by aerobic biofilms is highlighted on the basis of the results obtained using metabolites from planktonic cells and their agreement with most of the experimental evidences so far reported by other authors.

International Biodeterioration & Biodegradation, 2001

The susceptibility to bioremediation of the hydrocarbons contained in a waste from crude oil extr... more The susceptibility to bioremediation of the hydrocarbons contained in a waste from crude oil extraction was examined. Laboratory scale batch reactors were inoculated with indigenous bacteria and biodegradation was followed for 45 days. The total hydrocarbon content was reduced to ∼70% of its initial value at the end of the experiments. Saturated and aromatic hydrocarbons were the most readily degraded fractions with, respectively, ∼70% and ∼60% of the fraction remaining at the end of the experiment. A minor degradation was observed in the resins fraction (∼20%), whereas the asphaltenes fraction remained almost constant.The substrate preferences of the natural population towards various fractions of the crude oil were determined by both the length of the lag phase and the slope of the exponential growth in a mineral salt-base medium containing either of the different hydrocarbon fraction as the sole source of carbon. The highest consumption rate for every fraction during the time course experiments was in agreement with the shortest lag phase and the greatest exponential growth slope in the corresponding selective media, indicating changes in the population composition.

Applied and Environmental Microbiology, 2001

The adhesion of Pseudomonas fluorescens (ATCC 17552) to nonpolarized and negatively polarized thi... more The adhesion of Pseudomonas fluorescens (ATCC 17552) to nonpolarized and negatively polarized thin films of gold was studied in situ by contrast microscopy using a thin-film electrochemical flow cell. The influence of the electrochemical potential was evaluated at two different ionic strengths (0.01 and 0.1 M NaCl; pH 7) under controlled flow. Adhesion to nonpolarized gold surfaces readily increased with the time of exposition at both ionic-strength values. At negative potentials (؊0.2 and ؊0.5 V [Ag/AgCl-KCl saturated {sat.}]), on the other hand, bacterial adhesion was strongly inhibited. At 0.01 M NaCl, the inhibition was almost total at both negative potentials, whereas at 0.1 M NaCl the inhibition was proportional to the magnitude of the potential, being almost total at ؊0.5 V. The existence of reversible adhesion was investigated by carrying out experiments under stagnant conditions. Reversible adhesion was observed only at potential values very close to the potential of zero charge of the gold surface (0.0 V [Ag/AgCl-KCl sat.]) at a high ionic strength (0.1 M NaCl). Theoretical calculations of the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy for the bacteria-gold interaction were in good agreement with experimental results at low ionic strength (0.01 M). At high ionic strength (0.1 M), deviations from DLVO behavior related to the participation of specific interactions were observed, when surfaces were polarized to negative potentials.

Water Research, 2010

P. fluorescens biofilm metabolism Microbiologically influenced corrosion (MIC) a b s t r a c t In... more P. fluorescens biofilm metabolism Microbiologically influenced corrosion (MIC) a b s t r a c t In this work we report the results of a combined biochemical and electrochemical study aimed to analyze both the growth of biofilms of Pseudomonas fluorescens on copper samples and its possible role in the instability of the metal/electrolyte interface. DNA and RNA were quantified along the time for biofilms grown on copper and glass to estimate both the growth of the bacterial population and its metabolic state (through the RNA/DNA ratio). The expression and specific activity of catalase were also determined to gain insight into their possible role in corrosion acceleration. The electrochemical behavior of the biofilm/copper interface was monitored by Linear Polarization Resistance (Rp) and electrochemical impedance spectroscopy (EIS) along the experiments.

International Biodeterioration & Biodegradation, 2002

ABSTRACT The adhesion of P. fluorescens (ATCC 17552) to copper, zinc and aluminium brass in the a... more ABSTRACT The adhesion of P. fluorescens (ATCC 17552) to copper, zinc and aluminium brass in the absence and presence of a surface oxide layer was evaluated performing comparative batch experiments with various times of exposition. The adhesion of this strain to bare copper and aluminium brass was extremely low even after of exposition. On aged samples, on the other hand, adhesion increased with time on both metals. The degree of bacterial adhesion to aged metals was found to follow the sequence zinc>aluminium brass>copper, and the differences were related to the composition of the oxide layer. The presence of ZnO in the layer strongly increased the adhesion due to the large co-ordination capacity of Zn2+ ions. Correlation was found between the water contact angle of the metal surface and the degree of bacterial adhesion showing that adhesion increases with the decrease in the contact angle. Bacteria were found to have a hydrophilic surface with a water contact angle of 23.5±2° as determined by the sessile drop method.

International Biodeterioration & Biodegradation, 2003

ABSTRACT The adhesion of a wild strain of Pseudomonas sp. to aged aluminium brass was evaluated m... more ABSTRACT The adhesion of a wild strain of Pseudomonas sp. to aged aluminium brass was evaluated modifying the pH and ionic strength of the electrolyte solution. Ionic strengths of 0.1 and 0.6M NaCl, and pH values of 2, 4, 6, and 8 were tested. The surface oxides composition was analysed in situ by reflectance spectroscopy and the water contact angle of oxides under n-hexane was determined.At low ionic strength the adhesion of bacteria increased as pH values raised. The occurrence of adhesion was correlated to the formation of an oxide layer on the samples. The presence of copper and zinc oxides was detected in the layer at pH values⩾4 at both ionic strengths. At low ionic strength the formation of (hydro)oxides was also observed.At high ionic strength (0.6M), the adhesion was strongly diminished throughout the range of pH values tested. No evidences of hydration of the oxide layer were found at this condition.The acid–base interaction capacity of the metal surface was observed to increase with the raising of pH accounting for both, the bacterial adhesion increase and the oxides hydration.

Applied and Environmental Microbiology, 2005

The effect of surface electrochemical polarization on the growth of cells of Pseudomonas fluoresc... more The effect of surface electrochemical polarization on the growth of cells of Pseudomonas fluorescens (ATCC 17552) on gold electrodes has been examined. Potentials positive or negative to the potential of zero charge (PZC) of gold were applied, and these resulted in changes in cell morphology, size at cell division, time to division, and biofilm structure. At ؊0.2 V (Ag/AgCl-3 M NaCl), cells elongated at a rate of up to 0.19 m min ؊1 , rendering daughter cells that reached up to 3.8 m immediately after division. The doubling time for the entire population, estimated from the increment in the fraction of surface covered by bacteria, was 82 ؎ 7 min. Eight-hour-old biofilms at ؊0.2 V were composed of large cells distributed in expanded mushroom-like microcolonies that protruded several micrometers in the solution. A different behavior was observed under positive polarization. At an applied potential of 0.5 V, the doubling time of the population was 103 ؎ 8 min, cells elongated at a lower rate (up to 0.08 m min ؊1 ), rendering shorter daughters (2.5 ؎ 0.5 m) after division, although the duplication times were virtually the same at all potentials. Biofilms grown under this positive potential were composed of short cells distributed in a large number of compact microcolonies. These were flatter than those grown at ؊0.2 V or at the PZC and were pyramidal in shape. Polarization effects on cell growth and biofilm structure resembled those previously reported as produced by changes in the nutritional level of the culture medium.