ABSTRACT
110Biosurfactants are well known for their biodegrading potential and low hazard to the environment which explains why they have very promising applications environmentally and biotechnologically. Majority of the studies reported were using mesophilic bacterial strains but this may cause problems as these strains were not able to survive after being applied to oil spills having a temperature above 50°C. Thermophilic bacterial species are able to grow on a hydrocarbon-containing medium at a temperature up to 50°C and suitable for use in microbial-enhanced oil recovery (MEOR) and oil-sludge clean-up. A thermophilic Bacillus sp. was isolated from hot spring Sungai Klah, Perak, Malaysia, and later identified as Anoxybacillus sp. using biochemical tests and 16S rRNA sequence analysis. Anoxybacillus sp. is a new genus compared with the well-studied Geobacillus sp. or Bacillus sp. The strain was screened as positive biosurfactant producer and the stability of biosurfactant was characterized under the influence of different range of temperature, pH, and salinity. The surface activity of the sample relatively remained stable between pH 10 and 12 indicating preference for alkaline conditions. At the temperature range 4-121°C, the surface tension activity of the biosurfactant was maintained and did not show any significant loss of activity but the most stable condition was at temperature 25°C (33.97 mN/m). The surface tension started to decline at 4% to 6% (w/v) sodium chloride but was stable within this range. Based on the stability of the biosurfactant under the influence of different range of temperature, pH, and salinity, biosurfactant showed promising potential in environmental cleaning applications.
