The effect of essential oils on the growth of bacteria from municipal wastewater treatment
thesisposted on 23.05.2021, 09:44 by Syed M. Raza Bokhari
Bacterial sensitivity to essential oils has been reported in the case of soil isolated bacteria, food isolated bacteria but there is little evidence available to support the fact that wastewater isolated bacteria show sensitivity to essential oils. Keeping in view this fact the present investigation aims to determine the wastewater isolated bacterial strains sensitivity to six commercially available plant essential oils including clove, cinnamon, oregano, tea tree, fennel, and wintergreen. The essential oils were tested against ten laboratory bacterial strains (Acinetobacter baumanii, Escherichia coli: DH5α, E.coli: AD202, Pseudomonas fluorescens, Pseudomonas poae, Pseudomonas putida, staphylococcus aureus, and Stenotrophomonas maltophilia) (2) and ten wastewater isolated bacterial strains (Acinetobacter baumanii, Acinetobacter bouretii, Aeromonas hydrophila, E.coli, Enterobacter cloaceae, Flavobacterium branchiophilum, Klebsiella pneumoniae, Pseudomonas staurtii, Serratia fonticola, and Staphylococcus muscae) using the Kirby-Bauer disc diffusion assay, and the broth tube macrodilution MIC assay. The disc-diffusion assay showed that three of the oils, clove, cinnamon and oregano, were the most effective at inhibiting the growth of all the known single isolates. The broth tube MIC assay found that the WWTP isolated bacterial strains such as E. coli, Staphylococcus muscae, Enterobacter cloaceae, Acinetobacter baumanii were most sensitive to clove oil at MIC concentration ≤ 0.52 mg/ml, cinnamon oil at MIC concentration ≤ 0.51 mg/ml, and oregano oil MIC concentration ≤ 0.47 mg/ml. Finally, wastewater microbial community samples from activated sludge, returned sludge and anaerobic digesters were reduced by 0% > 94.24%, 46% > 99%, 70% > 97% percent when tested against clove, cinnamon, and oregano oils.