Production of lipopeptide biosurfactant by Bacillus subtilis GY19 and its application as oil-contaminated surface cleaning agent

Abstract

The present study investigated the effect of nutrient composition and pH on the lipopeptide production by Bacillus subtilis GY19. The maximum lipopeptide production (2.2 g/l) was achieved when the strain was grown in productive medium containing glycerol (4 g/l) and palm oil (0.75%, v/v) as substrates, sodium nitrate (0.5%, w/v) as nitrogen source, and glucose (1 g/l) and beef extract (0.5 g/l) as co-substrates with pH 7.5. In addition, the lipopeptide of B. subtilis GY19 could be applied for removal of slideway oil covered on metallic surface. Taguchi method was employed to evaluate the factors affecting the cleaning process. The results indicated that the presence of high levels of crude lipopeptide concentration positively affected surface washing efficacy. Further removal of slideway oil from the washing water could be achieved by the addition of immobilized oil-degrading bacterium, Acinetobacter sp. R2. The presence of lipopeptide increased the removal efficiency of slideway oil from 70% to 82% and did not show toxic effect on bacterial cells. This study shows promising ability of the lipopeptide from B. subtilis GY19 as a cleaning agent for oil-contaminated surface. In addition, it could subsequently enhance biodegradation of residual oil in the washing water.