Characterization of Biosurfactant Produced by Bacillus subtilis AS6 Isolated from Mangrove Sediment in Phuket Province

Abstract

This study was conducted to characterize the biosurfactant produced by Bacillus subtilis AS6 isolated from mangrove sediment in Phuket province. The extraction of biosurfactant from B. subtilis AS6 after cultured in mineral salt medium (MSM) for 54 hours was carried out by ammonium sulphate precipitation, acid precipitation and organic solvent extraction (chloroform: methanol). The results indicated that crude biosurfactant was recovered from the culture supernatant by chloroform: methanol (2:1) extraction with a yield of 0.45 g/l and had critical micelle concentration (CMC) of 0.044 g/l. The crude biosurfactant was capable to reduce surface tension of pH 6-9, temperature of 25-121°C and in the presence of NaCl up to 12% (w/v), MgCl₂ up to 0.1% (w/v) and CaCl₂ up to 0.04% (w/v). The biosurfactant obtained was purified by using column chromatography. Structure elucidation of partially purified biosurfactant performed by Fourier transform infrared spectroscopy (FT-IR) and Mass spectroscopy indicated that biosurfactant produced by B. subtilis AS6 consisted of amino acid and lipid with molecular mass of 1,032 m/z.