Biosurfactant production by haloalkaliphilic Bacillus strains isolated from Red Sea, Egypt

This study aimed to produce biosurfactant by extremophilic marine bacteria. Twenty-one oil-spilled seawater samples were collected from Shalateen, Red Sea, Egypt. Two promising morphologically distinct biosurfactant-producing marine bacteria, SH20 and SH24, were selected. They were grown on minimal salt medium (MSM) and the biosurfactant production was evaluated and detected after 24 h using drop collapsing test, blood hemolysis, emulsification index and surface tension. SH20 and SH24 isolates showed the highest emulsification index 57 and 56%, respectively, and have positive results for hemolysis and drop collapse. The two isolates were identified using 16 S rRNA as Bacillus amyloliquefaciens SH20 and Bacillus thuringiensis SH24. Stability of biosurfactant production by both strains was observed at moderate temperature (30 °C), high alkalinity at pH (11) and high salt concentration (15%). An increase of emulsification index tended to be 60 and 69%, respectively, considering the two strains haloalkiphilic bacteria. To study the stability mechanism for extremophilic biosurfactant producers, the protein profile was determined using SDS-PAGE electrophoresis showing some new detected proteins depends on their culturing conditions. Partially purified biosurfactant from the most active strain B. amyloliquefaciens SH20 was chemically determined by FTIR and GC-MS analysis showed characteristic bands, revealed the presence of non-anionic didemnin surfactant.