Biosurfactant-producing bacteria recovered from hydrocarbon contaminated soil in Awka, Anambra State, Nigeria

The increasing concern over environmental sustainability and the adverse ecological impact of synthetic surfactants has fueled interest in microbial biosurfactants as safer and more sustainable alternatives. Biosurfactants are valued for their biodegradability, low toxicity, and stability under extreme environmental conditions. 

The aim of this study was to isolate, characterize, and determine the effects of environmental parameters on biosurfactant-producing bacteria from hydrocarbon-contaminated soils in Anambra State, Nigeria. 

Samples from hydrocarbon contaminated soil from different locations in Awka, Anambra state were examined for biosurfactant-producing bacteria. Distinct colonies recovered and purified, were partially characterized and then subjected to preliminary screening tests which include drop collapse, oil spreading and emulsification index for biosurfactant production. The isolate with the highest biosurfactant production was further identified and characterized using 16S rRNA gene sequencing. The effects of carbon and nitrogen sources on biosurfactant production were examined. The crude biosurfactant produced by the isolate was extracted and its stability assessed under different temperature, pH, and salinity conditions. 

Four bacterial isolates were recovered and one of them was observed to produce an emulsification index (E₂₄) above 50% for all the substrates tested. The isolate was identified as Ochrobactrum anthropi MO419. Sucrose (2%w/v) and NH₄NO₃ (0.1%w/v) gave the highest biosurfactant production. The biosurfactant was stable at 100^oC, pH 3-11, and 1-10% NaCl concentration. 

This study reveals the ability of O. anthropi to produce stable biosurfactant under optimized conditions, making it a promising candidate for applications in environmental bioremediation, enhanced oil recovery, and pharmaceutical formulations.