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Mechanisms of Corrosion Caused by Anaerobic Biofilms and Its Mitigation Using a Biocide Enhanced by D-Amino Acids

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2017, Master of Science (MS), Ohio University, Biomedical Engineering (Engineering and Technology).

Microbiologically influenced corrosion (MIC), also known as biocorrosion, is a major problem in the oil and gas industry and water utilities. The same problem also exists with biomedical implants inside the human body. Although these medical implants are usually made of corrosion resistant stainless steel alloys or titanium, they still can experience MIC. MIC problems that occur on implants can be even worse sometimes because some places inside the human body (e.g., mouth) contain more bacteria and are more ideal growth environments than pipelines. Among all the microorganisms that cause MIC, sulfate-reducing bacteria (SRB) are often blamed because sulfate is ubiquitous in nature. Chapter 1 discussed various MIC issues facing different industries. Chapter 2 provided a review of various microbes that cause MIC problems on carbon and stainless steels.

In order to mitigate MIC, the underlying mechanism must be analyzed. The Ohio University MIC Research Group proposed the biocatalytic cathodic sulfate reduction (BCSR) theory, discussed in Chapter 2, which not only explains the bioelectrochemistry of the SRB MIC process but also overcomes the shortcoming of the previous cathodic depolarization theory (CDT) that is only applicable to hydrogenase-positive SRB. Chapter 4 confirmed the BCSR theory with SRB starvation and overfeeding tests using 304 stainless steel. It was confirmed that SRB MIC is due to SRB harvesting electrons from extracellular iron oxidation for sulfate reduction in order to generate energy when there is a local shortage of organic carbon molecules. Chapter 6 investigated the impact of liquid/headspace volume ratio on MIC by Desulfovibrio vulgaris. It was found that a large headspace allowed more H2S to escape from the culture medium to the headspace and this increased culture medium pH, however, did not statistically influence the weight losses of coupons in 100 ml culture medium and in 50 ml culture medium in the 125 ml vials. It was recommended that future tests should use a fixed volume of the culture medium with different vial sizes.

Biofilms cause MIC, thus, MIC mitigation is about biofilm treatment. Biocides have been used to treat biofilms. However, prolonged use of biocides leads to microbial resistance and thus dosage escalation. One way to combat this is to use biocide enhancers that make biocides more effective. D-amino acids are naturally occurring chemicals that have been found to disperse biofilms. Some of them, such as D-tyrosine and D-methionine, have been proposed as biocide enhancers in the literature. In Chapter 3, D-leucine, D-aspartic acid, and D-asparagine were investigated individually to see whether they could be enhancers of tetrakis (hydroxymethyl) phosphonium sulfate (THPS) and determine their efficacies against D. vulgaris biofilms on carbon steel. The results showed that D-leucine and D-aspartic acid demonstrated a promising enhancing ability for THPS at concentrations of 1000 ppm and 400 ppm, respectively. A D-alanine substitution test was conducted to confirm the mechanism suggesting that D-amino acids work as biocide enhancers through substitution of the D-alanine terminus in the peptidoglycan molecules in the bacterial cell wall. A different way to mitigate biofilms other than using biocides is to use anti-bacterial stainless steels. Chapter 5 investigated the copper-containing 2205 duplex stainless steel’s biofilm inhibition abilities. It was found that this novel metal inhibited the nitrate-reducing Pseudomonas aeruginosa biofilm. However, it promoted the growth of the D. vulgaris biofilm.

Tingyue Gu, Ph.D (Advisor)
Douglas Goetz, Ph.D (Committee Member)
Monica Burdick, Ph.D (Committee Member)
Peter Coschigano, Ph.D (Committee Member)
115 p.

Recommended Citations

Citations

  • Cai, W. (2017). Mechanisms of Corrosion Caused by Anaerobic Biofilms and Its Mitigation Using a Biocide Enhanced by D-Amino Acids [Master's thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1505752144462679

    APA Style (7th edition)

  • Cai, Weizhen. Mechanisms of Corrosion Caused by Anaerobic Biofilms and Its Mitigation Using a Biocide Enhanced by D-Amino Acids. 2017. Ohio University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1505752144462679.

    MLA Style (8th edition)

  • Cai, Weizhen. "Mechanisms of Corrosion Caused by Anaerobic Biofilms and Its Mitigation Using a Biocide Enhanced by D-Amino Acids." Master's thesis, Ohio University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1505752144462679

    Chicago Manual of Style (17th edition)