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 7 days of incubation in 50 mL anaerobic vials containing 40 mL culture medium at pH 7.0, the sessile cell counts indicated that 50 ppm (w/w) THPS + 30 ppm (w/w) trehalase led to an extra 5.7-fold sessile cell reduction when compared with the 50 ppm 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 50 ppm THPS alone treatment (with 9.0 μm and 1.0 mg/cm2). The biofilm images corroborated the decreased sessile cell count and pitting corrosion.