Bioremediation is gaining favorable attention as a more economical and environmentally friendly technique for the remediation of crude oil hydrocarbons. This makes the search for crude oildegrading microbes very crucial. In this study, the isolation and identification of actinobacteria in soil samples from a selected crude oil spill site were carried out. Eighteen isolates from different soil depths (20-120 cm) were screened for their ability to grow on crude oil-based medium (COBM). Actinomyces naeslundii, Actinomyces viscosus, Actinomyces israelii, Actinomyces meyeri, and Nocardia formicae from a 20 cm soil depth exhibited higher growth profiles on COBM than on glucose-based medium (GBM). A. viscosus and A. isrealii exhibited 5-and 3-fold increase in growth over GBM and were selected for biodegradation studies. Growth kinetics and residual crude oil were used to measure the degradation efficiency of A. viscosus and A. israeli over varying crude oil concentrations. Surprisingly, A. viscosus and A. isrealii achieved 98% degradation of 10 g/L crude oil in 12 days and 97% degradation of 30, 50, and 75 g/L in 16 and 18 days, respectively. Specific activity of total peroxidase was assayed over the biodegradation period. Peroxidase activity increased with degradation efficiency of A. viscosus and A. isrealii, suggesting that peroxidases play a key role in the crude oil biodegradation process. The unique tolerance exhibited by A. viscosus and A. israelii to crude oil and high crude oil degradation efficiencies indicate their promising potential for bioremediation applications.
The disadvantages associated with conventional treatment of crude oil pollution have led to the development of alternative, economical and reliable biological treatments. In this study, six actinobacterial isolates were obtained from 120cm soil depth of a selected crude oil contaminated site in the Niger Delta region of Nigeria. Streptomyces albus was selected from the six isolates based on its comparative ability to growth on crude oil and was investigated for its ability to degrade varying concentration of crude oil (1.0, 3.0, 5.0 and 7.5 %) and produce peroxidase during the biodegradation period. Increase in biomass enhanced degradation efficiency above 80 % after 10 days for all concentration of crude oil studied. Peroxidase production increased maximally during the log phase of growth with a maximum production of (3.01 U/L) on day 10 for 3% crude oil and (2.08 U/L) for 5% crude oil medium on day 12. These remarkable properties displayed by Streptomyces albus in this study showed how tolerant and efficient this actinobacterial isolate was toward varying concentration of crude oil vis-à-vis the production of peroxidase.
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