Center for Biofilm Engineering (CBE)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/9334
At the Center for Biofilm Engineering (CBE), multidisciplinary research teams develop beneficial uses for microbial biofilms and find solutions to industrially relevant biofilm problems. The CBE was established at Montana State University, Bozeman, in 1990 as a National Science Foundation Engineering Research Center. As part of the MSU College of Engineering, the CBE gives students a chance to get a head start on their careers by working on research teams led by world-recognized leaders in the biofilm field.
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Item Ennoblement of stainless steel studied by x-ray photoelectron spectroscopy(1998) Olesen, Bo H.; Avci, Recep; Lewandowski, ZbigniewItem Chemical effects of biofilm colonization on 304 stainless steel(1996-05) Pendyala, Jyostna; Avci, Recep; Geesey, Gill G.; Stoodley, Paul; Hamilton, Martin A.; Harkin, GaryChanges in the surface concentrations of the main alloying elements of an as‐received 304 stainless steel, exposed to a mixed culture of biofilm‐forming bacteria under flowing conditions, were observed using Auger electron spectroscopy. In the oxide film close to the bulk stainless steel, there was an enrichment in the relative concentration of Cr with a corresponding decrease in the relative Fe concentration as compared to a control coupon exposed only to sterile media. There were no changes observed in the relative Ni concentration.Item Influence of surface features on bacterial colonization and subsequent substratum chemical changes of 316l stainless steel(1996-01) Geesey, Gill G.; Gillis, Richard J.; Avci, Recep; Daly, Don Simone; Hamilton, Martin A.; Shope, Paul A.; Harkin, GaryBiofilm-forming bacteria were found to selectively colonize specific surface features of unpolished 316L stainless steel exposed to flowing aqueous media. Depending on the types of bacteria present, selective colonization resulted in significant depletion of Cr and Fe relative to Ni in the surface film at these features. No such depletion was observed on uncolonized surfaces exposed to sterile flowing aqueous medium. The results demonstrate that non-random, initial colonization of 316L stainless steel surfaces by these bacteria leads to changes in alloy elemental composition in the surface film that are enhanced with time. These chemical changes may be a critical step that weakens the oxide film at specific locations, allowing halides such as Cl− ions greater access to the underlying bulk alloy, and thereby facilitates localized attack and pit formation and propagation.Item Corrosion of mild steel underneath aerobic biofilms containing sulfate-reducing bacteria. part ii: at high dissolved oxygen concentration(1993-11) Lee, Whonchee; Lewandowski, Zbigniew; Morrison, Michael L.; Characklis, William G.; Avci, Recep; Nielsen, P. H.Microbial biofilms containing sulfate‐reducing bacteria (SRB) and general anaerobic bacteria (GAB) were grown in a closed flow channel reactor in air‐saturated bulk liquid. The SRB proliferated within anaerobic microniches even when dissolved oxygen penetrated the entire biofilm at some locations. Corrosion of mild steel during aerobic/anaerobic biofilm accumulation was classified as aerobic corrosion and SRB‐enhanced corrosion. Aerobic corrosion dominated during the early stages of biofilm accumulation. The corrosion rate decreased as the biofilm became more uniform over the surface. SRB‐enhanced corrosion occurred after the SRB community was established within the deposits and significant amounts of iron sulfides contacted the bare steel surface. The initiation and propagation of SRB‐enhanced corrosion in an aerobic/anaerobic biofilm system was explained through the establishment of an FeS/Fe galvanic cell.Item Corrosion of mild steel underneath aerobic biofilms containing sulfate-reducing bacteria. part i: at low dissolved oxygen concentration(1993-11) Lee, Whonchee; Lewandowski, Zbigniew; Okabe, Satoshi; Characklis, William G.; Avci, Recep; Nielsen, P. H.The sulfate‐reducing bacteria (SRB)‐enhanced corrosion of mild steel in the presence of 1.5 mg·l−1 dissolved oxygen (DO) in bulk liquid was investigated. The biofilm process analysis was combined with microelectrode measurements, electrochemical measurements, and surface analysis. In the early stages of biofilm accumulation, the cathodic polarization and the decreasing corrosion rate were attributed to DO consumption by aerobic bacteria. During that time, limited SRB activity was observed. The DO concentration near the steel surface was between 0.6 and 1 mg·l−1. After total depletion of dissolved oxygen near the steel surface, the cathodic depolarization and the increased corrosion rate were associated with the proliferation of SRB near the steel surface. Auger electron spectroscopy analysis indicated localized sulfide attack. High pit density appeared where the coincidence of oxygen and sulfur occurred. The bottom of the pit was enriched with sulfur.Item Stability in aqueous media of 316l stainless steel films deposited on internal reflection elements(1993-02) Pedraza, A. J.; Godbole, M. J.; Bremer, Philip J.; Avci, Recep; Drake, B.; Geesey, Gill G.Thin films of 316L stainless steel were sputter-deposited on cylindrical internal reflection elements (IREs) made of germanium. These films are intended for use in Fourier transform infrared (FT-IR) spectroscopy studies on the stability of stainless steel in aqueous media. In these deposits the films tend to peel off the substrate when immersed in water, probably due to galvanic corrosion at the metal/substrate interface. Deposition of a 2-nm-thick layer of chromium oxide on the substrate prior to the deposition of the steel was beneficial on three counts. It provided an electrically insulating layer, it enhanced adhesion, and it solved the steel/germanium incompatibility problem. It was also found that annealing the substrate prior to deposition remarkably enhances the film adhesion and improves the optical properties of the substrate. The microstructure, the topography, and the chemical composition of the films were characterized by scanning and transmission electron microscopy, Auger electron spectroscopy, and atomic force microscopy. The only significant difference between the austenitic stainless steel target material and the film is that the crystalline structure of the film is body-centered cubic. The optical properties of the system germanium/metallic film/water were studied and calculated with the help of a computer program. The absorbance of the water bands in the IR range was measured in coated Ge-IRE.Item Pit initiation on 316l stainless steel in the presence of bacteria leptothrix discophora(2001-01) Geiser, Michael Joseph; Avci, Recep; Lewandowski, ZbigniewEnnoblement of stainless steel by microbially deposited manganese oxides can cause pitting corrosion of the SS in natural waters at low chloride concentrations, leading to unexpected material failures. To study the effects of microbially deposited manganese oxides on pit initiation, we exposed 316L stainless steel to manganese oxidizing bacteria Leptothrix descophora under well-defined laboratory conditions. We then placed the ennobled coupons in a solution of low concentration sodium chloride until pitting initiated. The pits had different morphologies that those initiated by electrochemical polarization, hypothetically indicating a direct involvement of the bacteria in pit initiation.Item Microbially initiated pitting on 316l stainless steel(2002-06) Geiser, Michael Joseph; Avci, Recep; Lewandowski, ZbigniewPitting corrosion of 316L stainless steel ennobled in the presence of manganese-oxidizing bacteria, Leptothrix discophora, was studied in a low-concentration sodium chloride solution. Corrosion coupons were first exposed to the microorganisms in a batch reactor until ennoblement occurred, then sodium chloride was added, which initiated pitting. The pits had aspect rations (length divided by width) and shapes closely resembling the aspect ration and the shape of the bacteria, which suggested that the microorganisms were involved in pit initiation.Item Microbially deposited manganese and iron oxides on passive metals - their chemistry and consequences for material performance(2002-09) Shi, X.; Avci, Recep; Lewandowski, ZbigniewThe open-circuit potential (OCP) values of Type 316L (UNS S31603) stainless steel and Ti-6Al-4V (UNS R56400) corrosion coupons, exposed to fresh river water, were ennobled to as high as 365 mV vs saturated calomel electrode (SCE) and 400 mVsce respectively. With microchemical imaging capabilities and high-detection sensitivity, a surface analysis technique based on time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was developed to identify the oxidation states and distribution of biominerals on the ennobled metal surfaces. ToF-SIMS spectra of the microbial deposits compared to spectra of different manganese and iron mineral standards indicated that the biominerals on the metal surfaces are a mixture of ferric oxide (Fe2O3), manganese oxide (Mn3O4), and manganese oxyhydroxide (MnOOH) on fully ennobled coupons, and a mixture of iron oxide (Fe3O4), Fe2O3, Mn3O4, and manganese(III) oxide (Mn2O3) on partially ennobled coupons. Biomineralized manganese and iron oxides on the Type 316L stainless steel surfaces, regardless of the oxidation states, endanger the material integrity in a similar manner, as evidenced by the elevated OCP and increased cathodic current density upon mild polarization.Item Biofouling and corrosion of stainless steels in natural waters(2002) Lewandowski, Zbigniew; Avci, Recep; Geiser, Michael Joseph; Braughton, K. R.; Yurt, NurdanThe noble shift in corrosion potential to values between +300 and +400 mVSCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.