Optimization of biosurfactant production by Bacillus thuringiensis c25 isolated from palm oil contaminated soil

Abstract

Biosurfactants of microbial origin have wide applicability because of their surface-active potentials. Bacillus thuringiensis c25 isolated from palm oil contaminated soil was used in the production of biosurfactant and the product was screened using emulsification stability test (E24), drop-collapse, oil spreading, blood hemolysis and surface tension tests. The effects of incubation period, temperature, pH, and carbon source on biosurfactant production by B. thuringiensis c25 were investigated with a view to optimizing the production process. The biosurfactant produced was characterized using Fourier Transform Infrared Spectroscopy and Gas Chromatography-Mass Spectrometry. Initial assay showed emulsification index of 57.24 ± 0.25 %, oil displacement of 6.17 ± 0.21 mm and a positive drop-collapse test. Growth of B. thuringiensis at the optimal conditions of temperature 35 ºC, pH 7.0, glucose 10 g/L and yeast extract 1.5 g/L, reduced surface tension to 27.71 ± 0.88 mN/m and increased emulsification index to 84.78 ± 0.44%. Maximum biosurfactant production of 2.70 ± 0.04 g/L was obtained at 72 h. The characterization showed a lipopeptide biosurfactant type. Consequently, the B. thuringiensis of the present study is a good biosurfactant producer.

Keywords

• b. thuringiensis
• biosurfactants
• emulsification index
• surface tension
• palm oil