Abstract

Four bacterial strains belonging to the family Bacillaceae were isolated from a polluted site and tested for their efficiency in degrading a refinery effluent highly polluted with hydrocarbons. Among 13 strains isolated, four were selected for their efficiency. Each of these four strains demonstrated a strong ability to grow as a single strain on a hydrocarbon effluent (HCE) as sole carbon source. In batch assays using clarified wastewater as diluent, the strains achieved high-percentage decreases in total hydrocarbon concentration within 18 days: 98% with Bacillus licheniformis STK08,87% with Geobacillus stearothermophilus STM04, 80% with Lysinibacillus sphaericusSTZ75 and 72% with Bacillus firmus STS84. The decreases were greater during the first three days of treatment, with 73, 66, 39 and 47% recorded for Bacillus licheniformis STK08, G. stearothermophilus STM04, L. sphaericus STZ75 and B. firmus STS84, respectively. Growth assays run under different conditions showed thatB. licheniformis STK08 and G. stearothermophilus STM04 were able to grow at salinities of up to 120 g/L and at 55°C. Potential biosurfactant production tested using two methods namely modified drop collapse (MDC) and blue agar plate (BAP) demonstrated that the four Bacillaceae species are biosurfactant producers.

Key words: Hydrocarbons, biodegradation, pure culture, high salinity, high temperature.