Terrestrial bacterial isolate capability of producing surface-active biosurfactant: genetic identification,...

The present study aims to evaluate the efficiency of bacterial isolate to produce biosurfactant through nine analytical methods based on surface activity measurements. Bacterial isolate designated 13(1) showed capability to produce surfactant resulting in significant surface tension reduction of minimal salt culture broth medium with 42.84% corresponding to surface activity of 19.48 mN m^-1 and effectively emulsified soybean oil with E24% value reached 41.07%. This bacterium gave positive results in CTAB test indicating presence of extracellular anionic surfactants. Also, it gave highest oil dispersing zone with 2.22 cm diameter corresponding to 3.86 cm² area, and largest flatten droplet with 7.5 mm diameter on hydrophobic surface. Moreover, isolate 13(1) effectively produced lipases and had hydrocarbon degrading and hemolytic activities. Furthermore, the isolated bacterial strain was identified as Brucella anthropi OL469515 based on its morphological, cultural and biochemical characteristics, and analysis of 16S rRNA gene sequence. More interestingly, the biosurfactant production and cell growth were evaluated through five culture media including minimal salt, Hua, modified Hua, Bushnell Haas, and Kim media to investigate the more suitable medium ingredients for the efficiency and magnitude of biosurfactant production. Results have shown that maximum biosurfactant production obtained when B. anthropi grown on Hua medium leading to highest reduction of culture surface tension reached 45.81% with surface activity of 20.30 mN m^-1. Also, largest oil clearing zone was occurred with 2.45 cm diameter with area value of 4.73 cm². Finally, these comparable results concluded that Hua medium is the most suitable production medium to be used for biosurfactant optimization in future studies.