Antimicrobial and Anticorrosion Effect of Essential oils of Medicinal and Aromatic Plants on Sulphate Reducing Bacteria isolated from Oilfield Produced Water

Medicinal and Aromatic Plants (MAPs) have been known to possess inherent anti-microbial properties. In the present study, locally available essential oils of Lemongrass (LEO) (Cymbopogon flexuosus), Citronella (CEO) (Cymbopogon winterianus) and Patchouli (PEO) (Pogostemon cablin) were analyzed to ascertain their antimicrobial and anticorrosion effects on a native strain of Sulphate Reducing Bacteria (SRB),isolated from produced water sourced from an Oil Collecting Station in India’s North-Eastern state of Assam. The Minimum Inhibitory Concentration (MIC) for Lemongrass, Citronella and Patchouli essential oils were determined to be 50 ppm, 100 ppm and 450 ppm respectively, using microdilution susceptibility tests. The minimum concentration of the essential oils that not only inhibit SRB activity, but also kill the target bacterial cells was also determined using Minimum Bactericidal Concentration (MBC) assay. The MBC concentrations of LEO, CEO and PEO were found to be similar to their MIC levels. All the essential oils tested showed SRB biofilm inhibitory effects on glass and N-80 carbon steel coupons. The average rate of biocorrosion calculated based on the weight loss of N-80 steel coupons indicate that the essential oils tested were able to exhibit a significant anticorrosion effect on the treated N-80 steel coupons.