Degradative Ability of Silver Particles Synthesized by Gram-negative Bacteria of Some Crops Rhizosphere on Crude Oil Polluted Soil

Aim: To degrade the crude oil polluted soil with silver particles synthesized by some Gram negative rhizosphere bacteria of cocoa, orange and timber obtained from Idanre, Ondo State, Nigeria.

Place and Duration of Study: Soil samples were obtained from Idanre, Ondo State while crude oil polluted soil samples were obtained from Zion town in Ese- Odo at Ilaje, Ondo State, between June and September 2018. Also, Bonnylight Crude oil was collected from Warri in Nigeria. This research work was carried out at the Department of Microbiology Laboratory, Federal University of Technology, Akure.

Methodology: Soil samples (rhizosphere) were collected in sterile polythene bags and tightly packed and transported for analysis. The types and loads of bacteria present in the soil samples were determined. Identification and characterization of various bacterial isolates were based on Gram staining techniques and different biochemical tests. The physicochemical properties of the crude oil polluted soil were determined. The microbial biomass and the synthesis of silver particles were carried out while the bioremediation of the crude oil polluted soil with the silver particles which were performed in triplicate. Also, bioremediation of crude oil with the bacterial isolates were performed in triplicate. Five millilitres (5 ml) of silver particles produced was inoculated into 50 g of sterilized crude oil polluted soil in a plastic container with 5ml of basal medium and 3 ml of the harvested cells of the isolates was inoculated into 10 ml of the basal medium with 30ml of crude oil in a conical flask. The unsterilized soil without inoculum and silver particles were served as control, also crude oil without inoculum and silver nanoparticles were served as a control.

Results: Citrobacter freundii, Yersinia pestis, Edwardsiella tarda, were isolated from rhizosphere of cocoa. Serratia marcescens, Providencia stuatii were isolated from rhizosphere of orange while Enterobacter agglutinate, Moellerella wisconsis were isolated from rhizosphere of timber. The silver particles bioremediation on polluted soil ranges were recorded within 5 days interval for 30 days. It was deduced that Enterobacter sp appeared to be the fastest on polluted soil followed by Citrobacter sp, Providencia sp, Serratia sp and Yersinia sp.

Conclusion: Findings from this study revealed the effects of rhizosphere Gram negative bacteria in cleaning up crude oil polluted soil environment and the usefulness of silver particles in remediating hydrocarbon polluted soil.