Production of Biosurfactants by Actinomycetes Isolated from Hydrocarbon Contaminated Soils and Ikpoba River Sediments in Benin-City, Nigeria

Abstract

The production of biosurfactants by Actinomycetes isolated from hydrocarbon contaminated soils and Ikpoba river sediments were evaluated. Soil samples were collected from mechanic workshops located in various parts of Benin City and Ikpoba river sediments. Physico-chemical analyses were performed. Isolation of Actnomycetes was done using starch casein agar incorporation with antibiotics incubated for 7 – 10 days at 30^oC. Growth on mineral salt medium initiated the production of biosurfactants which was extracted by centrifugation and filtration followed by liquid extraction using chloroform: methanol (2:1v/v). Characterization and stability studies were conducted. The pH of the contaminated soil was 4.92 +/- 0.049 while that of Ikpoba river sediments was 6.62+/-0.056. The hydrocarbon contaminated soils had a higher concentration of surphur, nitrogen, potassium, sodium, magnesium and manganese compared to Ikpoba River, but only chlorine concentration was higher in Ikpoba River. Aerobic Gram positive rods with extensive branching were observed confirming growth of Streptomyces sp. The result showed stability across different temperature ranges with no significant difference observed in the two sites in emulsification activity (P>0.05). There was significant difference observed in the mean surface tension of the biosurfactants produced from the two sites across different temperature ranges with hydrocarbon contaminated soil having higher values (P>0.05). There was also significant surface tension difference between pH2 and pH8 (P<0.05) suggesting higher activity within those ranges. The result also show stability across different salt concentrations and had foaming characteristics. Actinomycetes have complex enzymatic mechanism that aids hydrocarbon mineralization and thus increases the potential for biosurfactant production. These biosurfactants are stable across temperature ranges and are not majorly affected by salt concentration; this property aids its potential usage in decontamination of oil contaminated areas in the Niger Delta region of Nigeria and other countries.

Keywords: Biosurfactants, Actinomycetes, hydrocarbon contaminated soils and Ikpoba river sediments