Abstract:
This research aimed at bioremediating crude oil polluted soil with silver nanoparticles synthesized by some fungi. Soil samples were collected with the aid of soil auger depth of 10 cm from rhizosphere (root) of cocoa and orange obtained from Federal University of Technology, Akure. Crude oil polluted soil was prepared by mixing 50 gram each of sterile soil into 10 ml of sterile bonny light crude oil in eight plastic rubbers and was kept for 7 days. Isolation of fungi from rhizosphere soil was carried out by standard microbiological techniques. Silver nanoparticles (AgNPs) were synthesized from the isolates using standard procedures and they were characterized by ultraviolet-Vis spectroscopy and fourier transmission infrared spectroscopy (FTIR). Bioremediation of crude oil polluted soil was done using standard method and monitored for 40 days, the set us was terminated and degradation of the crude oil in the soil was analyzed using gas chromatography mass spectroscopic analysis (GC-MS). The results revealed that seven fungi isolated from above rhizosphere soils were Nigrospora sphaerica, Penicillium discolor, Penicillium digitatum, Neurospora crassa, Alternarium infectoria, Trichophyton verrucosum and Mucor mucedo. The colour transformation from yellow to brown indicate the formation of silver nanoparticles. The UV-Vis analysis revealed that all samples showed an intense peak in the wavelength range of 410-440 nm. The FTIR analysis of silver nanoparticles synthesized by Nigrospora sphaerica, Penicillium discolor, Penicillium digitatum, Neurospora crassa, Alternarium infectoria, Trichophyton verrucosum and Mucor mucedo revealed the existence of a band at different stretches of bonds at different peaks of 3314.36 cm-1, 3310.47 cm-1, 2412.22 cm-1, 3912.33 cm-1 3614.52 cm-1 , 3852.11 cm-1 and 2112.11 cm-1 respectively. The silver nanoparticles produced by fungi isolates had ability to utilize or metabolize more classes of compound in crude oil except those of long n-alkane chain lengths (tetradecane, pentadecane, hexadecane etc.). The AgNPs synthesized by Alternarium infectoria and Neurospora crassa were able to degrade aliphatic and aromatic components in the crude oil than those produced by other fungal isolates. Therefore, AgNPs synthesized by Alternarium infectoria. and Neurospora crassa isolated from cocoa and orange trees rhizosphere can be expoited for decontamination of crude oil polluted soil.
