Hydroxymethyl Phosphonium Research Articles

Biomimetic aerogel coatings for flexible polyurethane foams with superior flame retardancy, mechanical flexibility and antibacterial properties

Flexible polyurethane foams (FPUFs) are widely used in various industries due to its high rebound characteristics, but its inherent flammability significantly affects its application. In this study, inspired by the structure of shell nacre, an aerogel coating with gelatin, boric acid and tetrakis hydroxymethyl phosphonium sulfate (THPS) as raw materials was designed. Owing to the hydrogen bonding interactions among the above molecules, the aerogel coating exhibits strong interfacial adhesion to the FPUF substrate, and the peel strength even surpasses the intrinsic strength of the FPUF matrix. Moreover, the coated FPUFs exhibit exceptional flame retardant and thermal insulation properties. The LOI value reaches as high as over 80 % and easily achieves a UL-94 V0 rating. During combustion, the coated FPUFs illustrate extremely low heat and smoke release. Meanwhile, the coated FPUFs still maintain excellent resilience. In addition, the THPS endows coated FPUFs with excellent antibacterial properties and exhibits a highly inhibition against Escherichia coli and Staphylococcus aureus.

Fe0-to-microbe electron transfer corrosion of EH36 steel by planktonic cells of Desulfovibrio vulgaris mediated by riboflavin

This study investigated the Fe0-to-microbe extracellular electron transfer (EET) corrosion of EH36 steel by planktonic Desulfovibrio vulgaris cells using Tetrakis hydroxymethyl phosphonium sulfate (THPS), peptide E6, and riboflavin (RF) as tools. 60 min after 20 ppm THPS & E6 injection and 50 ppm THPS injection, there was no difference in sessile cell counts, but planktonic cell counts were different. The subsequent injection of 20 ppm RF accelerated D. vulgaris MIC in varying degrees within minutes. This was attributed to RF-mediated EET of planktonic cells to accelerate corrosion, which can be further confirmed by the elevated expression levels of cytochrome c.

Acceleration mechanism of riboflavin on Fe0-to-microbe electron transfer in corrosion of EH36 steel by Pseudomonas aeruginosa

Riboflavin (RF), as a common electron mediator that can accelerate extracellular electron transfer (EET), is usually used as a probe to confirm EET-microbiologically influenced corrosion (MIC). However, the acceleration mechanism of RF on EET-MIC is still unclear, especially the effect on gene expression in bacteria. In this study, a 13-mer antimicrobial peptide E6 and tetrakis hydroxymethyl phosphonium sulfate (THPS) were used as new tools to investigate the acceleration mechanism of RF on Fe0-to-microbe EET in corrosion of EH36 steel caused by Pseudomonas aeruginosa. 60 min after 20 ppm (v/v) THPS and 20 ppm THPS & 100 nM E6 were injected into P. aeruginosa 1 and P. aeruginosa 2 (two glass bottles containing P. aeruginosa with different treatments) at the 3-d incubation, respectively, P. aeruginosa 1 and P. aeruginosa 2 had a similar planktonic cell count, whereas the sessile cell count in P. aeruginosa 1 was 1.3 log higher than that in P. aeruginosa 2. After the 3-d pre-growth and subsequent 7-d incubation, the addition of 20 ppm (w/w) RF increased the weight loss and maximum pit depth of EH36 steel in P. aeruginosa 1 by 0.7 mg cm−2 and 4.1 μm, respectively, while only increasing those in P. aeruginosa 2 by 0.4 mg cm−2 and 1.7 μm, respectively. This suggests that RF can be utilized by P. aeruginosa biofilms since the corrosion rate should be elevated by the same value if it only acts on the planktonic cells. Furthermore, the EET capacity of P. aeruginosa biofilm was enhanced by RF because the protein expression of cytochrome c (Cyt c) gene in sessile cells was significantly increased in the presence of RF, which accelerated EET-MIC by P. aeruginosa against EH36 steel.

Ultrafast gelling bioadhesive based on blood plasma and gelatin for wound closure and healing

Tissue adhesives offer a plethora of advantages in achieving efficient wound closure over conventional sutures and staples. Such materials are of great value, especially in cases where suturing could potentially damage tissues or compromise blood flow or in cases of hard-to-reach areas. Besides providing wound closure, the tissue adhesives must also facilitate wound healing. Previously, plasma-based tissue adhesives and similar bioinspired strategies have been utilized to aid in wound healing. Still, their application is constrained by factors such as high cost, diminished biocompatibility, prolonged gelation times, inadequate swelling, quick resorption, as well as short-term and inconsistent efficacy. To address these limitations, we report the development of a highly biocompatible and ultrafast-gelling tissue adhesive hydrogels. Freeze-dried platelet-rich plasma, heat-denatured freeze-dried platelet-poor plasma, and gelatin were utilized as the base matrix. Gelation was initiated by adding tetrakis hydroxymethyl phosphonium chloride. The fabricated gels displayed rapid gelation (3–4 s), low swelling, increased proliferation, and migration against L929 cells and had porcine skin tissue adhesion strength similar to that of plasma-based commercial glue (Tisseel®).

Mitigation of Desulfovibrio ferrophilus IS5 degradation of X80 carbon steel mechanical properties using a green biocide.

Most microbiologically influenced corrosion (MIC) studies focus on the threat of pinhole leaks caused by MIC pitting. However, microbes can also lead to structural failures. Tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide mitigated the microbial degradation of mechanical properties of X80 steel pipeline by Desulfovibrio ferrophilus (IS5 strain), a very corrosive sulfate reducing bacterium. It was found that 100 ppm (w/w) THPS added to the enriched artificial seawater (EASW) culture medium before incubation resulted in 2.8-log reduction in sessile cell count after a 7-d incubation at 28 °C under anaerobic conditions, leading to 94% uniform corrosion rate reduction (from 1.3to 0.07mm/a), and 84% pitting corrosion rate reduction (from 0.70to 0.11mm/a). The X80 dogbone coupon incubated with 100 ppm THPS for 7 d suffered 3% loss in ultimate tensile strain and 0% loss in ultimate tensile strength compared with the abiotic control in EASW. In comparison, the no-treatment X80 dogbone coupon suffered losses of 13% in ultimate tensile strain and 6% in ultimate tensile stress, demonstrating very good THPS efficacy.

Eco-friendly bifunctional antibacterial and anticorrosive broad-spectrum rosin thiourea iminazole quaternary ammonium salt against microbiologically influenced corrosion

Bifunctional antibacterial and anticorrosive broad-spectrum rosin thiourea iminazole quaternary ammonium salt (RTIQAS) was investigated to inhibit microbiologically influenced corrosion (MIC) caused by anaerobic gram-negative sulfate reducing bacterium (SRB) Desulfovibrio vulgaris against X80 carbon steel and aerobic gram-positive bacterium Bacillus licheniformis against 316L stainless steel. It also indicated that RTIQAS was more effective than common commercial biocides THPS (tetrakis hydroxymethyl phosphonium sulfate) and glutaraldehyde at the same concentration against X80 carbon steel corrosion by D. vulgaris. In the molecular simulation, the interaction energy confirmed the favorable adsorption of RTIQAS on the metal surfaces, indicating its potential as an effective corrosion inhibitor.

Electrochemical investigation of the “double-edged” effect of low-dose biocide and exogenous electron shuttle on microbial corrosion behavior of carbon steel and copper in enriched seawater

The microbiologically influenced corrosion (MIC) behavior of carbon steel and copper induced by SRB was investigated by low levels of the biocide tetrakis hydroxymethyl phosphonium sulphate (THPS) and the environmental electron shuttle riboflavin in early incubation and harsh conditions. After 7 days of incubation, riboflavin weakened the inhibition for SRB by THPS in the carbon steel system, but did not apply to the copper. Thirty ppm THPS inhibited planktonic cell proliferation, but still formed visual biofilms on carbon steel and copper surfaces. In the co-existence of THPS and riboflavin, higher corrosion rates were obtained in carbon steel, while the MIC of copper was mitigated. For the harsh biotic systems, thirty ppm THPS was ineffective against the SRB-MIC of the harsh systems. Riboflavin was the icing on the cake for carbon steel under this condition, accelerating the SRB-MIC process. Electrochemical noise currents were used to monitor the effects of chemical injection in harsh conditions.

The development of chrome free chestnut and Tetrakis Hydroxymethyl Phosphonium Sulfate based Eco-benign combination tanning system

The replacement of the conventional chromium tanning system with an eco-benign tanning systems has received great attention owing to stringent environmental regulations. In this specific study, a chrome-free combination tanning system based on chestnut and tetrakis (hydroxymethyl) phosphonium sulfate (THPS) was developed and presented as an effective alternative cleaner tanning technology. Processing of the tanning trials were carried out varying the percentages of chestnut as a tannage, followed by THPS as a re-tannage for process optimization. The leathers obtained were characterized for their thermal stability, grain surface properties using a scanning electron microscope, physical strength characteristics, comfort, and organoleptic properties. Finally, the environmental impact of the tanning systems was assessed through the comparative analysis of their spent liquors. The chestnut-THPS combination system tanned leathers using 20 % chestnut followed by 2 % THPS resulted in maximum shrinkage temperature of 95OC. The hydrothermal stability of the leathers tanned using this combination tanning system were found to be better than those tanned using chestnut and THPS tanning systems alone, respectively. The strength and comfort properties of the leathers produced using the developed combination tanning system were found to be on par with or better than those of conventionally tanned leathers, and the scanning electron microscopic study depicted that the grain surface of the leathers produced were observed to be free of surface deposition. The environmental impact assessment showed that the combination tanning system used resulted in a significant reduction in TS, TDS, TSS, and BOD in the wastewater. This research article has attempted and established the use of chestnut-THPS-based combination tanning systems as an effective, eco-friendly alternative tanning process technology.

Effects of different water quality regulators on growth performance, immunologic function, and domestic water quality of GIFT tilapia.

Water quality regulation is widely recognized as a highly effective strategy for disease prevention in the field of aquaculture, and it holds significant potential for the development of sustainable aquaculture. Herein, four water quality regulators, including potassium monopersulfate (KMPS), tetrakis hydroxymethyl phosphonium sulfate (THPS), bacillus subtilis (BS), and chitosan (CS), were added to the culture water of Oreochromis niloticus (GIFT tilapia) every seven days. Subsequently, the effects of these four water quality regulators on GIFT tilapia were comprehensively evaluated by measuring the water quality index of daily growth-related performance and immune indexes of GIFT tilapia. The findings indicated that implementing the four water quality regulators resulted in a decrease in the content of ammonia nitrogen, active phosphate, nitrite, total organic carbon (TOC), and chemical oxygen demand (COD) in the water. Additionally, these regulators were found to maintain dissolved oxygen (DO) levels and pH of the water effectively. Furthermore, using these regulators demonstrated positive effects on various physiological parameters of GIFT tilapia, including improvements in final body weight, weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), feed conversion ratio (FCR), spleen index (SI), hepato-somatic index (HSI), immune cell count, the activity of antioxidant-related enzymes (Nitric oxide, NO and Superoxide dismutase, SOD), and mRNA expression levels of immunity-related factors (Tumor Necrosis Factor-alpha, TNF-α and Interleukin-1 beta, IL-1β) in the liver and spleen. Notably, the most significant improvements were observed in the groups treated with the BS and CS water quality regulators. Moreover, BS and CS groups exhibited significantly higher serum levels of albumin (ALB) and total protein (TP) (P < 0.05), whereas the other indicators showed no significant difference (P > 0.05) compared to the control group. However, the KMPS and THPS groups of GIFT tilapia exhibited significantly higher serum levels of aspartate aminotransferase (AST), alanine transaminase (ALT), creatinine (CRE) and blood urea nitrogen (BUN) (P < 0.05), whereas they exhibited significantly decreased HSI (P < 0.05). In addition, the partially pathological observations revealed the presence of cell vacuolation, nuclear shrinkage, and pyknosis within the liver. In conclusion, these four water quality regulators, mainly BS and CS, could improve the growth performance and immunity of GIFT tilapia to varying degrees by regulating the water quality and then further increasing the expression levels of immune-related factors or the activity of antioxidant-related enzymes of GIFT tilapia. On the contrary, the prolonged use of KMPS and THPS may gradually diminish their growth-enhancing properties and potentially hinder the growth of GIFT tilapia.

Mitigation of EH36 ship steel biocorrosion using an antimicrobial peptide as a green biocide enhancer

In this study, a 13-mer antimicrobial peptide (RRWRIVVIRVRRC) named by E6 was used as an enhancer of a green biocide to mitigate the biocorrosion of EH36 ship steel. Results show that a low concentration of E6 (100 nM) alone was no-biocidal and could not resist the Desulfovibrio vulgaris adhesion on the EH36 steel surface. However, E6 enhanced the bactericidal effect of tetrakis hydroxymethyl phosphonium sulfate (THPS). When E6 and THPS were both added to the bacteria and steel system, both the sessile D. vulgaris cells and biocorrosion rate of EH36 steel decreased significantly. Compared with the 80 ppm THPS alone treatment, the combination of 100 nM E6 + 80 ppm THPS led to an extra 1.6-log reduction in the sessile cell count. Fewer sessile D. vulgaris cells led to a lower extracellular electron transfer (EET) rate, directly resulting in 78% and 83% decreases in weight loss and pit depth of EH36 steel, respectively. E6 saved more than 50% of THPS dosage in this work to achieve a similar biocorrosion mitigation effect on EH36 steel.

Electrochemical Assessment of Mitigation of Desulfovibrio ferrophilus IS5 Corrosion against N80 Carbon Steel and 26Cr3Mo Steel Using a Green Biocide Enhanced by a Nature-Mimicking Biofilm-Dispersing Peptide.

MIC (microbiologically influenced corrosion) is problematic in many industries, especially in the oil and gas industry. In this work, N80 carbon steel for pipelines was tested with 26Cr3Mo chromium pipeline steel for comparison in SRB (sulfate-reducing bacterium) MIC mitigation using a THPS (tetrakis hydroxymethyl phosphonium sulfate)-based commercial biocide (Biotreat 5475 with 75-80% THPS by mass). Peptide A, a nature-mimicking synthetic cyclic peptide (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with biofilm dispersal ability was used as a biocide enhancer. Metal coupons covered with 3-d old Desulfovibrio ferrophilus IS5 biofilms were immersed in different biocide solutions. After 1-h treatment, 200 ppm Biotreat 5475, 200 ppm Biotreat 5475 + 200 nM (360 ppb) Peptide A, and 400 ppm Biotreat 5475 achieved 0.5-log, 1.7-log and 1.9-log reductions in sessile cell count on N80, and 0.7-log, 1.7-log, and 1.8-log on 26Cr3Mo, respectively. The addition of 200 nM Peptide A cut the THPS biocide dosage by nearly half. Biocide injection tests in electrochemical glass cells after 1 h exhibited 15%, 70%, and 72% corrosion inhibition efficiency (based on corrosion current density) on N80, and 27%, 79%, 75% on 26Cr3Mo, respectively. Linear polarization resistance and electrochemical impedance spectrometry results also indicated antimicrobial efficacies.

Sensitivity of a bone-equivalent polymer gel dosimeter for measuring the dose to bone during radiation therapy.

Treatment planning systems that use the Monte Carlo algorithm can calculate the dose to the medium (Dm) in non-water-equivalent tissues such as bones. However, Dm cannot be verified using actual measurements; therefore, it is necessary to develop tissue-equivalent dosimeters. In this study, we developed a bone-equivalent polymer gel dosimeter (BPGD) that can measure the dose absorbed by the bone and investigated its sensitivity. The BPGDs were prepared by adding 3.0mol of calcium hydrogen phosphate dihydrate as a component of bone to an improved dose-sensitive polyacrylamide gelatin and tetrakis hydroxymethyl phosphonium chloride (iPAGAT). One day after preparation, the BPGDs were irradiated with a field size of 15 × 15 cm2 using a 10 MV X-ray beam to evaluate the dose sensitivity, dose-rate dependence, and dose-integration dependence. One day after dose exposure, the BPGDs were scanned using a 0.4T MRI APERTO Eterna (Hitachi, Tokyo, Japan) to obtain R2 values. The difference between the R2 values of 6Gy and 0Gy was up to 5s-1, and the R2 curve plateaued in the high-dose region. Moreover, the BPGD did not depend on the integration of the dose and dose rates. Therefore, the BPGDs that we developed can determine the radiation dose to bones.

Biocompatible and bioactive hydrogels of recombinant fusion elastin with low transition temperature for improved healing of UV-irradiated skin.

Prolonged exposure to UV radiation can cause severe photodamage to the skin, leading to abnormal fragmentation of elastin fibers. As one of the main protein components of the dermal extracellular matrix, elastin plays a critical role in the mechanical behavior and physiological function of the skin. Animal-derived elastin has attracted extensive attention in tissue engineering, however it suffers from severe drawbacks such as a risk of virus transmission, ready degradation, and challenging quality control. Herein, we have for the first time developed a novel recombinant fusion elastin (RFE) and its cross-linked hydrogel for improved healing efficacy for UV-irradiated skin. RFE showed temperature-sensitive aggregation behavior similar to natural elastin. Compared with recombinant elastin without the fusion V-foldon domain, RFE showed a much more ordered secondary structure and lower transition temperature. Furthermore, Native-PAGE results indicated that the addition of the V-foldon domain triggered the formation of remarkable oligomers in RFE, which may result in a more ordered conformation. Tetrakis Hydroxymethyl Phosphonium Chloride (THPC) cross-linking of RFE led to the production of a fibrous hydrogel with uniform three-dimensional porous nanostructures and excellent mechanical strength. The RFE hydrogel showed superior cellular activity, significantly promoting the survival and proliferation of human foreskin fibroblast-1 (HFF-1). Studies of mice models of UV-irradiated skin demonstrated that the RFE hydrogel pronouncedly accelerated their healing process by inhibiting epidermal hyperplasia as well as boosting the regeneration of collagen and elastin fibers. The highly biocompatible and bioactive recombinant fusion elastin and its cross-linked hydrogel provide a potent treatment for photodamaged skin, which may have promising applications in dermatology and tissue engineering.

Simultaneously removal of phosphorous and COD for purification of organophosphorus wastewater by catalytic ozonation over CaO

Organic phosphorous wastewater is very hard to be purified which need to remove both COD and phosphorous. The treatment process of organic phosphorous wastewater is commonly complicated. In this work, CaO has been used as the catalyst and precipitant for the treatment of organophosphorus wastewater by catalytic ozonation. Compared with CeO2, MnO2 and MgO, CaO shows excellent catalytic performance for the removal of COD. Additionally, the generated PO33− can be removed by Ca2+. Ca2+ can catalyze the reaction between O3 and H2O to generate active oxygen species, such as •OH, -•O2, 1O2. Besides, various conditions, namely, amount of catalyst, O3 flow rate, substrate concentration and pH for the degradation of Tetrakis Hydroxymethyl Phosphonium Sulfate (THPS) wastewater by catalytic ozonation over CaO have been optimized to determine the optimal parameter conditions. Finally, the excess Ca2+ in the solution can be removed by the addition of CO2.

Mitigation of carbon steel biocorrosion using a green biocide enhanced by a nature-mimicking anti-biofilm peptide in a flow loop

Biocorrosion, also called microbiologically influenced corrosion (MIC), is a common operational threat to many industrial processes. It threatens carbon steel, stainless steel and many other metals. In the bioprocessing industry, reactor vessels in biomass processing and bioleaching are prone to MIC. MIC is caused by biofilms. The formation and morphology of biofilms can be impacted by fluid flow. Fluid velocity affects biocide distribution and MIC. Thus, assessing the efficacy of a biocide for the mitigation of MIC under flow condition is desired before a field trial. In this work, a benchtop closed flow loop bioreactor design was used to investigate the biocide mitigation of MIC of C1018 carbon steel at 25 °C for 7 days using enriched artificial seawater. An oilfield biofilm consortium was analyzed using metagenomics. The biofilm consortium was grown anaerobically in the flow loop which had a holding vessel for the culture medium and a chamber to hold C1018 carbon steel coupons. Peptide A (codename) was a chemically synthesized cyclic 14-mer (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with its core 12-mer sequence originated from a biofilm dispersing protein secreted by a sea anemone which possesses a biofilm-free exterior. It was used as a biocide enhancer. The combination of 50 ppm (w/w) THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide + 100 nM (180 ppb by mass) Peptide A resulted in extra 1-log reduction in the sulfate reducing bacteria (SRB) sessile cell count and the acid producing bacteria (APB) sessile cell count compared to 50 ppm THPS alone treatment. Furthermore, with the enhancement of 100 nM Peptide A, extra 44% reduction in weight loss and 36% abatement in corrosion pit depth were achieved compared to 50 ppm THPS alone treatment.Graphical

Mouthpiece polymer-gel dosimeter for in vivo oral dosimetry during head and neck radiotherapy

In this study, we developed a mouthpiece-type gel dosimeter to prevent the oral mucositis caused by the perturbation effect of dental alloys in the radiotherapy of the head and neck regions and to enable in vivo dosimetry. Understanding the dose distribution in the oral cavity during radiotherapy helps identify the possible site for oral mucositis during treatment. Here agarose, which has a higher melting point than gelatin, was added as a coagulant to stabilize the shape of the dosimeter. The strength and dose response of the dosimeter were investigated. The strength was measured at room temperature, 20°C–40 °C, which is higher than the intraoral temperature. The dose–response curves were obtained by magnetic resonance imaging with R2 ranging from 0 to 25 Gy. The strength and dose response of the mouthpiece-type gel dosimeter were approximately 4 and 2.1 times higher than those of polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride dosimeters commonly used in the prescribed doses per fraction of treatment. The dosimeter is composed of 4 wt% MgCl2 and 1.5 wt% agarose; thus, it can retain the water equivalence. Through in vivo oral dosimetry in three dimensions for head and neck radiotherapy with dental alloys using the mouthpiece-type gel dosimeter, we obtained three-dimensional dose distributions in the dosimeter. The properties of the dosimeter show that it can be used in the clinic, depending on the prescribed dose.

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

• Peptide A is a non-biocidal biofilm dispersal agent for biocide enhancement. • 20 ppm (w/w) THPS is insufficient to mitigate D. ferrophilus MIC of X80 steel. • 20 ppm THPS is enhanced by 100 ppb Peptide A, achieving 83% lower weight loss. • It also achieves 4-log extra sessile cell reduction compared with 20 ppm THPS. • 20 ppm THPS + 100 ppb Peptide A weight loss is similar to that for 50 ppm THPS. Tetrakis hydroxymethyl phosphonium sulfate (THPS) was enhanced by a 14-mer Peptide A, with its core 12-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 that 50 ppm (w/w) THPS was sufficient to mitigate the D. ferrophilus biofilm, and its very agressive MIC (19.7 mg/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% for 100 ppb Peptide A compared with 20 ppm THPS alone treatment, indicating that Peptide A was a good biocide enhancer for THPS.

Food-grade D-limonene enhanced a green biocide in the mitigation of carbon steel biocorrosion by a mixed-culture biofilm consortium.

Microbiologically influenced corrosion (MIC), or microbial biocorrosion, is caused directly by microbial metabolic activities/products or induced by microbial biofilm's damage of a protective film that exposes a solid surface to a pre-existing corrosive environment. MIC causes billions of dollars of losses in various industrial processes, especially in oil and gas and water utilities. The mitigation of problematic industrial microbes typically relies on biocides whose discharges can cause environmental problems. Thus, more effective biocide applications are desired to minimize environmental impact. D-Limonene, a citrus peel oil, generally regarded as safe (GRAS), was used to enhance the popular biodegradable tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide. An oilfield mixed-culture biofilm was grown anaerobically in enriched artificial seawater containing C1018 carbon steel coupons for 7days at 37°C. One hundred ppm (w/w) D-limonene reduced general heterotrophic bacteria (GHB) and acid-producing bacteria (APB) effectively, leading to 5.4-log and 6.0-log reductions in sessile GHB and APB cell counts, respectively, compared to no treatment control. The combination of 100ppm D-limonene + 100ppm THPS achieved extra 1.0-log SRB, 0.6-log GHB and 0.5-log APB reductions in sessile cell counts, which led to extra 58% reduction in microbial corrosion mass loss (1.2 vs. 0.5mg/cm2) and extra 30% reductions in maximum pit depth (11.5 vs. 8.1µm), compared to 100ppm THPS-only treatment. Linear polarization resistance and potentiodynamic polarization (PDP) corrosion data supported mass loss and pitting data. Mixed-culture biofilms on carbon steel coupons after 7day incubation at 37°C showing enhanced biocide treatment outcome using D-limonene + THPS: A no treatment, B 100ppm D-limonene, C 100ppm THPS, D 100ppm D-limonene + 100ppm THPS.

Evaluation of trehalase as an enhancer for a green biocide in the mitigation of Desulfovibrio vulgaris biocorrosion of carbon steel.

Trehalase can biocatalyze the conversion of trehalose to glucose. It is an enzyme that plays an important role in biofilm formation. Thus, trehalase has been patented as a chemical for preventing and treating biofilms. Sulfate-reducing bacteria (SRB) biofilms are often found responsible for biocorrosion, also known as microbiologically infuenced corrosion (MIC), especially in the oil and gas industries and in water utilities. The MIC treatment process typically requires biocide treatment of biofilms, sometimes together with scrubbing. Owing to environmental concerns, a lower biocide dosage is desired in the treatment process. In this work, trehalase was tested as a green biocide enhancer to enhance tetrakis hydroxymethyl phosphonium sulfate (THPS) in the prevention of Desulfovibrio vulgaris MIC of C1018 carbon steel in ATCC 1249 culture medium at 37°C. THPS is one of the most popular industrial biocides owing to its broad-spectrum efficacy and green chemical status. After 7days of incubation in 50mL anaerobic vials containing 40mL culture medium at pH 7.0, the sessile cell counts indicated that 50ppm (w/w) THPS + 30ppm (w/w) trehalase led to an extra 5.7-fold sessile cell reduction when compared with the 50ppm THPS alone treatment. As a consequence, the combination treatment also resulted in an extra 54% in pit depth reduction and 30% in weight loss reduction when compared with the 50ppm THPS alone treatment (with 9.0μm and 1.0mg/cm2). The biofilm images corroborated the decreased sessile cell count and pitting corrosion.

Novel Approaches for Biocorrosion Mitigation in Sewer Systems

Concrete sewer pipes can be corroded by the biogenic sulfuric acid (H2SO4) generated from microbiological activities in a process called biocorrosion or microbiologically induced corrosion (MIC). In this study, inhibitors that can reduce Acidithiobacillus thiooxidans growth and thus may reduce the accumulation of biofilm components responsible for the biodegradation of concrete were used. D-tyrosine, tetrakis hydroxymethyl phosphonium sulfate (THPS) and TiO2 nanoparticles were investigated as potential inhibitors of sulfur-oxidizing bacteria (SOB) growth. Results showed that most of the chemicals used can inhibit SOB growth at a concentration lower than 100 mg/L. TiO2 nanoparticles exhibited the highest biocide effect and potential biocorrosion mitigation activity, followed by D-tyrosine and THPS.