Nlemolisa, Oluchi Rose Collette2026-05-302026-05-302018-11Nlemolisa, O. R. C. (2018). Phenol utilization and toxicity of ternary mixtures of phenol, zinc and cadmium to fungal species isolated from hydrocarbon impacted soil [Unpublished Master's Thesis]. Federal University of Technology Owerri, Nigeriahttps://repository.futo.edu.ng/handle/20.500.14562/2792This thesis is for the award of Master of Science (MSc.) in Environmental MicrobiologyThe present study was carried out to determine phenol utilization and toxicity of ternary mixtures of zinc, cadmium and phenol to fungal species isolated from hydrocarbon impacted soil. The yeasts isolated from the hydrocarbon impacted soil were identified as Saprochaete sp. and Cryptococcus sp. The biodegradation phenol potential of Saprochaete sp. and Cryptococcus sp. was studied using mineral salt broth supplemented with phenol with concentration ranging from 0-1000 mg/l. Investigation shows that the yeasts were able to utilize almost all the introduced quantity (1000 mg/l) of phenol as sole source of carbon and energy within a period of 3 to14 days. The toxicity was determined based on the inhibition of dehydrogenase activity of Saprochaete sp. and Cryptococcus sp. The toxicity of chemicals and their mixtures was evaluated in the concentration range of 0-16 mM for phenol, 0-5 mM for zinc and 0-0.4 mM for cadmium. The binary and ternary mixture ratios were evaluated. The toxicity thresholds (IC50) were estimated using 3-parameter logistic dose-response model. The IC50 shows that cadmium has the highest toxic effect on the yeasts with IC50 value of 0.075 mM for Saprochaete sp. and 0.09 mM for Cryptococcus sp. The binary and ternary toxicity of the mixtures on the enzyme activity of the yeasts was evaluated with toxic index (TI) model. Modulation of the toxic interactions by the components of the mixtures through synergistic, additive and antagonistic interactions on the heavy metals and phenol were possible against the dehydrogenase activity of the phenol-utilizing yeasts. However the toxic effects of phenol and heavy metals would depend on their relative amount present in the environment.enAttribution-NonCommercial-ShareAlike 4.0 InternationalBiodegradationdehydrogenase activitiesphenolheavy metalstoxic index modelDepartment of MicrobiologyMaster’s Thesis