Biosurfactant producing abilities of some bacteria isolated from bitumen contaminated soils

Bio-surfactants produced by bacteria are surface-active compounds required in the degradation of hydrocarbons. They are complex groups of surface-active molecules produced by microorganisms that stick to the specific cell covering or are secreted extracellularly in the growth medium. This study is aimed at determining the bio-surfactant-producing abilities of bacteria that are isolated from bitumen-polluted soil. Isolation of bacteria from bitumen-polluted soil samples was carried out using standard methods. The bio-surfactant producing ability of the isolated bacteria was investigated by several assays, including drop collapse test, tilting glass slide test, emulsification index, and foaming activity. Characterization of the isolated bacteria was carried out using 16S rRNA, and the extracted genome from each isolate was sequenced, showing the gene annotation of the isolates. Crystal violet biofilm analysis was carried out to determine the biofilm-producing ability of the isolated bacteria. The extracted bio-surfactant was characterized with Fourier Transform Infrared Spectroscopy (FTIR) spectra and Scanning Electron Microscopy (SEM). Whole-genome sequencing analysis was done on two best Bio-surfactant-producing bacteria. Characterization of the bacteria isolates by 16S rRNA showed their homology in the phylogenetic tree in which Lysinibacillus sphaericus belong to the clade of Lysinibacillus and Bacillus. The biofilm analysis revealed that all the isolates were biofilm producers, with one high producer, three moderate producers and one weak producer. The SEM spectra revealed the structure of the product produced, and FTIR confirmed their chemical nature, indicating rhamnolipids. The bio-surfactant results indicated that two isolates, Lysinibacillus sphaericus and Pseudomonas sp. were the best Bio-surfactant-producing isolates.