ABSTRACT
Microbiocides are used to control problematic microorganisms. High doses of microbiocides cause environmental and operational problems. Therefore, using microbiocide enhancers to make microbiocides more efficacious is highly desirable. 2,2-dibromo-3-nitrilopropionamide (DBNPA) is a popular biodegradable microbiocide. D-Amino acids have been used in lab tests to enhance microbiocides to treat microbial biofilms. In this investigation, D-tyrosine was used to enhance DBNPA against Desulfovibrio vulgaris biofilm on C1018 carbon steel. After 7 days of incubation, the mass loss of coupons without treatment chemicals in the ATCC 1249 culture medium was found to be 3.1 ± 0.1 mg/cm2. With 150 ppm (w/w) DBNPA in the culture medium, the mass loss was reduced to 1.9 ± 0.1 mg/cm2 accompanied by a 1-log reduction in the sessile cell count. The 150 ppm DBNPA + 1 ppm D-tyrosine combination attained an extra 3-log reduction in sessile cell count and an additional 30% reduction in mass loss compared with 150 ppm DBNPA only treatment. The combination also led to a smaller maximum pit depth. Linear polarization resistance (LPR), electrochemical impedance spectrometry (EIS), and potentiodynamic polarization (PDP) tests corroborated the enhancement effects.
