DefinePK

Abstract

The aim of this research was to study isolation, characterization and stability of biosurfactant-producing bacteria. One hundred and ninety-seven bacterial strains 69 from hot springs and 128 from garage sites were isolated from Northern Thailand and screened for biosurfactant production, determined for its activities by oil displacement area measurement, emulsification test and surface tension measurement on parafilm. Twenty-five strains of bacteria from garages site showed a promising biosurfactant production. Strain SCMU106 that presented the highest values of oil displacement area 143.20 cm2, emulsification index 60 and droplet formation on parafilm surface 8.0 mm was identified as Pseudomonas aeruginosa by 16S rDNA sequence analysis. Combination of 1 glucose plus 0.1 corn oil and 0.5 NH42H2PO4, as carbon and nitrogen source, respectively was the optimal biosurfactant producing condition. The effects of pH, salinity and temperature on the produced biosurfactant were also evaluated. The produced biosurfactant was non-cytotoxic and stable to high temperature, neutral to alkaline pH pH 6-10 and moderate concentration to electrolyte up to 8 NaCl.