ASSESSING THE CAPACITY OF WILD AND MUTANT STRAINS OF BACILLUS SUBTILIS AND PSEUDOMONAS PUTIDA ISOLATED FROM REFINERY EFFLUENT IN THE DEGRADATION OF HYDROCARBONS
ASSESSING THE CAPACITY OF WILD AND MUTANT STRAINS OF BACILLUS SUBTILIS AND PSEUDOMONAS PUTIDA ISOLATED FROM REFINERY EFFLUENT IN THE DEGRADATION OF HYDROCARBONS
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Date
2019-03
Authors
ORJIUDE, Ejike Josiah
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Abstract
Petroleum refinery effluents are characterized by the presence of pollutants such as hydrocarbons as such could be of serious environmental consequence if discharged into receiving sites without proper treatment to remove the pollutants. This study assessed the capacity of wild and mutant strains of Bacillus subtilis and Pseudomonas putida isolated from refinery effluent in the degradation of hydrocarbons present in the effluent. The physicochemical parameters of the raw and treated effluent samples collected from Kaduna Refinery and Petrochemical Company (KRPC) were determined using standard guidelines. With the exception of turbidity (35.3 and 18.2 NTU), BOD (190 and 29.6 mg/L), COD (351.2 and 78.1 mg/L) and Oil and Grease (45.2 and 17.9 mg/L) for the raw and treated effluent respectively, and conductivity (695 μS/cm) for the raw effluent, all other parameters were within the permissible limits set by FMENV. Six (6) and eleven (11) isolates of Bacillus subtilis and Pseudomonas putidarespectively were isolated from the effluent and screened for capacity to utilize and grow on mineral medium containing different concentrations (0.5%, 1%, 1.55% and 2%) of crude oil as the sole source of carbon. Isolates TE8 (B. subtilis) and TEC10 (P. putida) had luxuriant growth across the first three concentrations of crude oil and medium growth on medium containing 2% crude oil. Both isolates were treated with nitrous acid and UV- irradiation to generate mutants. Death rate of 59.67% (40.33% survival) and 66.33% (33.67% survival) were observed for Bacillus subtilis and Pseudomonas putida respectively on treatment with nitrous acid. Also death rate of 51.67% (48.33% survival) and 40% (60%) were observed for Bacillus subtilis and Pseudomonas putida respectively on exposure to UV- irradiation. The relative efficiency of hydrocarbon degradation by the wild and mutant strains was assessed by evaluating the Hydrocarbon utilizing bacterial (HUB) counts and changes in concentration of oil and grease at
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intervals of 3 days for 15 days. The UV-mutant strains had slightly higher HUB counts (2.73×108, 1.5×108 and 2.391×108) than the wild strains (2.73×108, 1.32×108 and 2.39×108) while the nitrous acid mutant strains had the lowest HUB counts (8.35×107, 8.13×107 and 5.07×107) for P. putida, B. subtilis and their co-culture respectively. Also, higher oil and grease degradation was observed in the UV-mutant strains with 96.23%, 92.60% and 99.38%, followed by the wild strains with 87.25%, 80.25% and 88.89% and the nitrous acid mutant strains with 80.25%, 68.52% and 81.48% oil and grease degradation for P. putida, B. subtilis and their co-culture respectively. It was therefore concluded that while wild strains of B. subtilis and P. putida are good hydrocarbon degrading agents, irradiation with UV results in increased efficiency and the co-culture of the bacteria were more efficient than the individual culture.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF SCIENCE (MSc) DEGREE IN MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY, FACULTY OF LIFE SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
ASSESSING,, CAPACITY,, WILD,, MUTANT STRAINS,, BACILLUS SUBTILIS,, PSEUDOMONAS PUTIDA ISOLATED,, REFINERY EFFLUENT,, DEGRADATION,, HYDROCARBONS