BIOREMEDIATION OF CRUDE OIL POLLUTED SOIL WITH SILVER NANOPARTICLES SYNTHESIZED BY BACTERIA ISOLATED FROM SOILS IN IDANRE, NIGERIA

Abstract

In this study, silver nanoparticles (AgNPs) synthesized by bacteria isolated from three different soils, rhizosphere of orange, cocoa and timber in Akure, Ondo state, Nigeria were examined for their degrading ability on crude oil polluted soil obtained from Zion town in Ese-Odo, Igbekebo Local Government, Ondo State. Bacteria were isolated from the above soil samples by using standard microbiological technique. Production of silver nanoparticles was done by using biomass of isolated bacteria and characterization wadone using UV-VIS spectroscopy and Fourier Transform Infrared spectroscopy (FTIR). Degradation of crude oil was done by using both the bacteria isolated and biosynthesized silver nanoparticles and the degrading ability of the AgNPs was determined using spectrophotometer at optical density of 540nm. Hydrocarbons residues after degradation were determined using gas chromatography. Bacteria isolated were Serratiamarcescens RHOR, Moellerella wisconsensis RHTB, Enterobacter agglomerans RHTB, Providencia stuartii RHOR, Citrobacter freundii RHCC, Escherichia coli RHCC, Yersinia pseudotuberculosis RHCC and Edwardsiella tarda RHCC, Salmonella Sp CPSL, Proteus mirabilis CPSL, Klebsiella pneumonia CPSL and Yersinia pestis CPSL.Silver nanoparticles (AgNPs) synthesis was confirmed by colour change from yellow to brownish. Bacteria that were able to synthesize AgNPs were Serratia marcescens RHOR, Enterobacter agglomerans RHTB, Providencia stuartii RHOR, Yersinia pseudotuberculosis RHCC and Citrobacter freundii RHCC. The maximum absorption for UV-VIS spectroscopy analysis was obtained at wavelength of 500nm for Serratia marcescens RHOR and 400nm for Enterobacter agglomerans RHTB, Providencia stuartii RHOR, Yersinia pseudotuberculosis RHCC and Citrobacter freundii RHCC respectively. The FTIR analysis of AgNPs revealed existence of a band at different stretches of bonds at different peaks of 3602.3cm-1, 3483.0cm-1,3626.5cm-1, 3615.2cm-1, and 3580.6cm-1 respectively. Silver nanoparticles (AgNPs) synthesized by Enterobacter agglomerans RHTB, Providencia stuartii RHOR, and Citrobacter freundii RHCC were able to degrade crude oil polluted soil on 30th day. Enterobacter agglomerans RHTB synthesized AgNPs reduced optical density from 2.30 on initial day to 0.18 on 30th day, Citrobacter freundii RHCC dropped from 2.30 to 0.25 and Providencia stuartii RHOR dropped from 2.30 to 0.27. Aliphatic compounds with carbon number 13 to 38 were detected in the crude oil polluted soil by gas chromatographic analysis. The addition of silver nanoparticles synthesized by Enterobacter agglomerans RHTB enhanced degradation of aliphatic compounds like nnanocosane c29.from 600pA to 420pA. Silver nanoparticles (AgNPs) synthesized by Enterobacter agglomerans RHTB, Providencia stuartii RHOR, and Citrobacter freundii RHCC in this study showed significant degrading ability. Enterobacter agglomerans RHTB synthesized silver nanoparticles obtained from this study is hereby recommended for degradation of crude oil and its polluted soil.