Multiple Applications of a Novel Cationic Gemini Surfactant: Anti-Microbial, Anti-Biofilm, Biocide, Salinity Corrosion Inhibitor, and Biofilm Dispersion (Part II)

Abstract

The Egyptian petroleum industries are incurring severe problems with corrosion, particularly corrosion that is induced by sulfidogenic microbial activities in harsh salinity environments despite extensively using biocides and metal corrosion inhibitors. Therefore, in this study, a synthesized cationic gemini surfactant (SCGS) was tested as a broad-spectrum antimicrobial, anti-bacterial, anti-candida, anti-fungal, anti-biofilm (anti-adhesive), and bio-dispersion agent. The SCGS was evaluated as a biocide against environmental sulfidogenic-bacteria and as a corrosion inhibitor for a high salinity cultivated medium. The SCGS displayed wide spectrum antimicrobial activity with minimum bactericidal/fungicidal inhibitory concentrations. The SCGS demonstrated anti-bacterial, anti-biofilm, and bio-dispersion activity. The SCGS exhibited bactericidal activity against environmental sulfidogenic bacteria and the highest corrosion inhibition efficiency of 93.8% at 5 mM. Additionally, the SCGS demonstrated bio-dispersion activity against the environmental sulfidogenic bacteria at 5.49% salinity. In conclusion, this study provides a novel synthesized cationic surfactant with many applications in the oil and gas industry: as broad-spectrum antimicrobial and anti-biofilm agents, corrosion inhibition for high salinity, biocides for environmentally sulfidogenic bacteria, and as bio-dispersion agents.

Keywords: anti-biofilm; bio-dispersion agent; biocidal activity; cationic gemini surfactant; corrosion inhibitor; mild steel; sulfidogenic bacteria.

Figure 1

The antimicrobial activity of the SCGS using a modified agar well diffusion method against (a) strains Staphylococcus aureus (DSMZ 3463), Bacillus subtilis (ATCC 6633), Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 9027), Candida albicans (ATCC 10231), and Aspergillus niger (ATCC 16404).

Figure 2

Minimum inhibitory (MIC) and minimum bactericidal/fungicidal (MBC/MFC) concentrations of the SCGS estimation using a two-fold micro dilution method in 96 well micro-titer plates in comparison to a positive control (inoculated with microorganism without the SCGS) and a negative control (only sterile media). The plates were visually elaborated using a resazurin as an oxidation-reduction indicator at a concentration of 0.015%. The well with no color change (blue resazurin) means negative result or no growth however the changed color (pink color) means positive result or there is bacterial growth. (a, b) Were the plates of Staphylococcus aureus (DSMZ 3463), Bacillus subtilis (ATCC 6633) with more dilution. (c) The plate of Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 9027). (d) The plate of Candida albicans (ATCC 10231) and Aspergillus niger (ATCC 16404).

Figure 3

Positive induced bacterial biofilms of Bacillus subtilis (ATCC 6633) and Escherichia coli (ATCC 8739) on a 24 dilution titer plates. (a) the cultivated biofilms on the plate surface, (b) the cultivated biofilms on the glass surface (1.0 × 1.0 × 0.3 cm), (c) the dried biofilms on the glass surface, (d) the scanning electron microscopy (SEM) images of Bacillus subtilis (ATCC 6633) (right side) and Escherichia coli (ATCC 8739) (left side).

Figure 4

The application of the cationic gemini surfactant (SCGS) at different concentrations (0.1, 0.5, 1.0, 5.0 mM) in comparison to control reactor (inoculated with enriched environmental sulfidogenic bacteria at a salinity of 5.49% NaCl), and blank reactor (un-inoculated with enriched environmental sulfidogenic bacteria at a salinity of 5.49% NaCl).

Figure 5

SEM images (a) the cleaned metal surface, (b) The sulfidogenic biofilm, (c) the metal surface (at a salinity of 5.49% NaCl) after removing the biofilm, and (d) the environmental sulfidogenic bacteria inoculated with 5 mM SCGS. Scale bar = 10 µm.

Figure 6

The bio dispersion activity of the SCGS on the metal surface against the environmental sulfidogenic bacteria at 5.49% salinity. (a) the cultivated sample (b) the coupons after washing (c) the bio-dispersion activity of the SCGS with concentration of 5, 2.5, 1.25, and 0.625 mM. The figure showed that the concentration of 1.25 mM is the MBEC of the SCGS on the metal surface against the environmental sulfidogenic bacteria at 5.49% salinity.

Figure 7

The chemical structure of the synthesized cationic gemini surfactant, 4,4′-(((1E,5E)-pentane-1,5-diylidene)bis(azanylylidene))bis(1-dodecylpyridin -1-ium) bromide [16]. The synthesis had a total yield of 91.3% (for more details see the supplementary materials).