ISOLATION AND CHARACTERIZATION OF SURFACE ACTIVE COMPOUNDS PRODUCED BY HALOPHILIC BACTERIA

Biosurfactants or bioemulsifiers produced by microorganisms is considered an essential step in hydrocarbon biodegradation in the marine environment. Four bacterial strains isolated from Maruit lake, Egypt displayed hemolytic activity when grown on blood agar. 16S rRNA sequencing revealed that these strains were affiliated to Halomonas, Chromohalobacter and Halobacillus. Bacterial adhesion to benzene, xylene and lubricant motor oil ranged between 60-80 % indicating the presence of surface active compounds. The 4 strains had the capacity to produce surface active compounds when grown with 1% of motor oil, rapeseed oil and olive oil as sole carbon source and in the presence of different NaCl concentrations (0.0, 0.5 and 1.0 M). Most of the strains showed enhanced growth in the presence of 0.5 and 1.0 M NaCl, emphasizing the importance of NaCl in controlling the growth of halophilic bacteria. Drop collapse test was positive in all strains. Surface tension measurements ranged between 72-58 mN/m for motor oil, olive oil and rapeseed oil. All the isolates exhibit emusification stability of 69-100% with the tested oils. Resultant emulsion found stable without any phase separation. We concluded that these strains have a potential application as a bioemulsifiers which can grow in different types of oils.