Effect of exogenous flavins on the microbial corrosion by Geobacter sulfurreducens via iron-to-microbe electron transfer

Microbes can cause or accelerate metal corrosion,leading to huge losses in corrosion damages each year.Geobacter sulfurreducens is a representative electroactive bacterium in many soils,sediments,and wastew-ater systems.It has been confirmed to directly extract electrons from elemental metals.However,little is known about the effect of electron shuttles in G.sulfurreducens corrosion on stainless steel.In this study,we report that exogenous flavins promote iron-to-microbe electron transfer,accelerating micro-bial corrosion.G.sulfurreducens caused 1.3 times deeper pits and increased electron uptake(with 2 times increase of i_(corr))from stainless steel when riboflavin was added to the culture medium.OmcS-deficient mutant data suggest that G.sulfurreducens utilizes riboflavin as a bound-cofactor in outer membrane c-type cytochromes.The finding that,in the presence of microbes,riboflavin can substantially accelerate corrosion highlights the role of flavin redox cycling for enhanced iron-to-microbe electron transfer by G.sulfurreducens and provides new insights in microbial corrosion.

Toward a better understanding of microbiologically influenced corrosion caused by sulfate reducing bacteria

Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H_2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H_2S gets its H^+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H_2S is responsible for SRB MIC of carbon steel. However, in recent years,well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer(EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.

Microbiologically influenced corrosion behavior of S32654 super austenitic stainless steel in the presence of marine Pseudomonas aeruginosa biofilm

S32654 super austenitic stainless steel(SASS) is widely used in highly corrosive environments. However,its microbiologically influenced corrosion(MIC) behavior has not been reported yet. In this study, the corrosion behavior of S32654 SASS caused by a corrosive marine bacterium Pseudomonas aeruginosa was investigated using electrochemical measurements and surface analysis techniques. It was found that P. aeruginosa biofilm accelerated the corrosion rate of S325654 SASS, which was demonstrated by a negative shift of the open circuit potential(EOCP), a decrease of polarization resistance and an increase of corrosion current density in the culture medium. The largest pit depth of the coupons exposed in the P.aeruginosa broth for 14 days was 2.83 m, much deeper than that of the control(1.33 m) in the abiotic culture medium. It was likely that the P. aeruginosa biofilm catalyzed the formation of CrO_3, which was detrimental to the passive film, resulting in MIC pitting corrosion.

Effects of d-Phenylalanine as a biocide enhancer of THPS against the microbiologically influenced corrosion of C1018 carbon steel

Microbiologically influenced corrosion(MIC) is caused by biofilms such as those of sulfate reducing bacteria(SRB). To mitigate MIC, biocide treatment is often needed. Tetrakis(hydroxymethyl) phosphonium sulfate(THPS) is an environmentally friendly biocide that is often used in the oil and gas industry. However, its prolonged use leads to biocide resistance, leading to dosage escalation. A biocide enhancer can be used to slow down the trend. In recent years, d-amino acids have been investigated as an enhancer for THPS and other biocides. Published works used anaerobic vials and flow devices, which could not reveal the real-time changes of the biocide treatment on corrosion. In this work, it was proven that the biocide enhancement effects of d-Phenylalanine(d-Phe) on THPS against the Desulfovibrio vulgaris biofilm on C1018 carbon steels could be assessed in real time using linear polarization resistance and electrochemical impedance spectroscopy to collaborate sessile cell count, weight loss and pitting depth data. The results showed that 500 ppm(w/w) d-Phe effectively enhanced 80 ppm THPS against MIC by the D. vulgaris(a corrosive SRB) biofilm. The sessile cell count and pit depth were all reduced with the enhancement of d-Phe.

Effect of Cu Addition to 2205 Duplex Stainless Steel on the Resistance against Pitting Corrosion by the Pseudomonas aeruginosa Biofilm

The effect of copper addition to 2205 duplex stainless steel(DSS) on its resistance against pitting corrosion by the Pseudomonas aeruginosa biofilm was investigated using electrochemical and surface analysis techniques. Cu addition decreased the general corrosion resistance, resulting in a higher general corrosion rate in the sterile medium. Because DSS usually has a very small general corrosion rate, its pitting corrosion resistance is far more important. In this work, it was shown that 2205-3%Cu DSS exhibited a much higher pitting corrosion resistance against the P. aeruginosa biofilm compared with the 2205 DSS control, characterized by no significant change in the pitting potential and critical pitting temperature(CPT) values. The strong pitting resistance ability of 2205-3%Cu DSS could be attributed to the copper-rich phases on the surface and the release of copper ions, providing a strong antibacterial ability that inhibited the attachment and growth of the corrosive P. aeruginosa biofilm.

Inhibition effects of benzalkonium chloride on Chlorella vulgaris induced corrosion of carbon steel

In this work,a surfactant,benzalkonium chloride(BAC),was used to study its effects on both the growth of Chlorella vulgaris and the corrosion caused by its biofilm.Experimental results indicated that BAC at a low concentration of 3 mg/L suppressed C.vulgaris growth and achieved 81%corrosion inhibition based on weight loss reduction.The inhibition effects increased when the BAC dosage was increased.At 30 mg/L,the corrosion inhibition increased to 95%.Electrochemical results supported surface pitting analysis,weight loss results data and confirmed the corrosion inhibition.

Microbiologically influenced corrosion of Cu by nitrate reducing marine bacterium Pseudomonas aeruginosa

The microbiologically influenced corrosion(MIC) mechanisms of copper by Pseudomonas aeruginosa as a typical strain of nitrate reducing bacteria(NRB) was investigated in this lab study.Cu was immersed in deoxygenated LB-NO3 seawater inoculated with P.aeruginosa and incubated for 2 weeks.Results showed that this NRB caused pitting and uniform corrosion.The maximum pit depths after 7 d and 14 d in125 mL anaerobic vials with 50 mL broth were 5.1 μm and 9.1 μm,accompanied by specific weight losses of 1.3 mg/cm2(7 d) and 1.7 mg/cm2(14 d),respectively.Electrochemical measurements corroborated weight loss and pit depth data trends.Experimental results indicated that extracellular electron transfer for nitrate reduction was the main MIC mechanism and ammonia secreted by P.aeruginosa could also play a role in the overall Cu corrosion process.

Microbial ingress and in vitro degradation enhanced by glucose on bioabsorbable Mg-Li-Ca alloy

Biodegradable magnesium alloys are challenging to be implanted in patients with hyperglycemia and diabetes.A hypothesis is suggested that glucose accelerates microbial ingress and in vitro degradation of Mg-Li-Ca implants.Corrosion resistance and mechanical properties was demonstrated using electrochemical,hydrogen evolution and tensile tests.The bacteria from Hank's solution were isolated via 16S rRNA gene analysis.The results revealed that Mg-1Li-1Ca alloy exhibited different responses to Hank's solution with and without glucose.The solution acidity was ascribed to Microbacterium hominis and Enterobacter xiangfangensis,indicating that glucose promoted microbial activity and degradation and deterioration in mechanical property of Mg-1Li-1Ca alloy.

Synergistic effect of chloride ion and Shewanella algae accelerates the corrosion of Ti-6Al-4V alloy

The increasing utilization of titanium alloys in marine environments makes their microbiologically influenced corrosion study a timely matter.This work demonstrated that the corrosion ofTi-6 Al-4 V alloy was accelerated by a marine bacterium Shewanella algae in 2216 E medium with different Cl-level.Various electrochemical,pitting morphology and passive film analyses demonstrated that S.algae weakened the passive film,which made Cl-more aggressive.The synergy of those two factors caused considerable corrosion acceleration of the titanium alloy,leading to a maximum pit depth of 3.2μm and corrosion current density of 26.5 nA cm_(-2) in 2216 E medium with 3.50%(w/w)Cl^(-).

RIGID GIGAPOROUS CHROMATOGRAPHIC MEDIA AND THEIR POTENTIAL IMPACT ON DOWNSTREAM PROCESSING

More and more biomolecules are being produced by the biotechnology industry for applications ranging from medicine and food to engineering materials. Liquid chromatography plays a center-stage role in a typical downstream process producing biomolecules such as recombinant proteins. Rigid gigaporous media are porous particles possessing large transecting through-pores with a pore-to-particle diameter ratio of dpore/dparticle＞ 0.01. They allow convective flow in the large through-pores, while the smaller diffusion-pores (typically several hundred angstroms in size) supply the needed surface areas. Because of the transecting gigapores, a portion of the mobile phase flows through the pores in addition to fluid flow in the interstitial spaces between the particles in a packed-bed column. This considerably lowers the operating column pressure drop. This lower pressure drop makes axial-direction scale-up of chromatographic columns possible to avoid pancake columns that invariably degrade separation resolution. The large gigapores also make the binding sites on the diffusion pore surfaces more accessible, thus increasing the loading capacity of large protein molecules that can be hindered sterically if only diffusion pores are present. This work discusses the development of rigid gigaporous media and their potential impact on the design of multi-stage downstream process from the angle of multi-scale analysis.

Mitigating microbiologically influenced corrosion of an oilfield biofilm consortium on carbon steel in enriched hydrotest fluid using 2,2-dibromo-3-nitrilopropionamide(DBNPA) enhanced by a 14-mer peptide

In the oil and gas industry,microbiologically influenced corrosion(MIC) is a major threat to hydrotest,a procedure which is required to certify whether a pipeline can be commissioned.Seawater is frequently used as a hydrotest fluid.In this bio film prevention lab study,an oilfield biofilm consortium was grown in an enriched artificial seawater anaerobically at 37℃ for 60 days.The combination of 100 ppm(w/w) 2,2-dibromo-3-nitrilopropionamide(DBNPA)+100 nM(180 ppb) Peptide A(a biofilm dispersal agent) led to extra SRB(sulfate reducing bacteria),APB(acid producing bacteria) and GHB(general heterotrophic bacteria) sessile cell count reductions of 0.9-log,0.8-log and 0.6-log,respectively,compared with the outcome obtained by using 100 ppm DBNPA only.The Peptide Aenhancement also led to extra reductions of 44 % in weight loss,43 % in maximum pit depth,and 54 % in corrosion current density.

Mitigation of sulfate reducing Desulfovibrio ferrophilus microbiologically influenced corrosion of X80 using THPS biocide enhanced by Peptide A

Tetrakis hydroxymethyl phosphonium sulfate(THPS) was enhanced by a 14-mer Peptide A, with its core12-mer sequence mimicking part of Equinatoxin II protein, in the mitigation of sulfate reducing Desulfovibrio ferrophilus MIC(microbiologically influenced corrosion) of X80 carbon steel. Results proved that50 ppm(w/w) THPS was sufficient to mitigate the D. ferrophilus biofilm, and its very agressive MIC(19.7mg/cm^(2) in 7 days or 1.31 mm/a), but not 20 ppm THPS. To achieve effective mitigation at a low dosage of THPS, biofilm-dispersing Peptide A was added to 20 ppm THPS in the culture medium. Sessile cell counts were reduced by 2-log and 4-log after enhancement by 10 ppb and 100 ppb Peptide A, respectively. Enhancement efficiency(further reduction in corrosion rate) reached 69% for 10 ppb Peptide A and 83% for100 ppb Peptide A compared with 20 ppm THPS alone treatment, indicating that Peptide A was a good biocide enhancer for THPS.

Tafel scan schemes for microbiologically influenced corrosion of carbon steel and stainless steel

1.Introduction Microbial biofilms cause microbiologically influenced corrosion(MIC),which is one of the operational risks that can lead to equipment failures in the oil and gas industry and other industries [1-4].Mitigation measures such as biocide treatment and corrosion monitoring programs are implemented to ensure vital equipment integrity [5,6].The mechanism investigations in MIC can assist case analyses,field detections and biocide treatment strategies [7-9].