No abstract

Among 64 bacterial strains isolated in this study, the best two of biosurfactant-producing bacteria were selected and identified based on the phenotypic properties and molecular approach based on 16S rRNA having 100% similarity to the gram-negative Enterobacter aerogenes B19 strain bacteria and rode gram-positive strain Bacillus cereus ISU-02 in the Nucleotide database of the National Center for Biotechnology Information. The study showed that two selected isolates gave the highest positive results that were used to investigate the biosurfactant production including: interfacial reduction, foaming activity, hemolytic activity, CTAB agar plate, drop collapse assay, oil displacement test and emulsification index E24%. Both Bacillus cereus ISU-02 strain and Enterobacter aerogenes B19 strain have reduced the interfacial tension to 27.61 and 28.93, respectively. Biosurfactants produced from both isolates were tested for oil recovery using spontaneous imbibition process. Bacillus cereus ISU-02 strain gave the highest oil recovery of 66.9% for rock permeability of 843 mD, followed by Enterobacter aerogenes B19 strain with oil recovery of 34% for rock permeability 197 mD, while the lowest rate of oil recovery was 12.1% for FW with permeability of 770 mD. An additional oil rate reached to 7.9% has been recovered from the residual oil when the core plug that was treated with formation water alone was retreated with the cell free biosurfactant supernatant. Use of the new biosurfactants has improved oil recovery better than use of formation water alone or formation water with the commercial surfactant SDS.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

In this study, 21 environmental bacterial isolates isolated from different environmental sources in Basra Governorate identified phenotypically and genetically based on 16 rRNA gene sequence analysis were screened to reveal their ability to produce biopolymer based on the viscosity scale formed in the cultural media and use of Sudan Black stain. Six isolates showed their ability to produce biopolymer, and the two isolates of Bacillus licheniformis strain CC91, Bacillus thuringiensis strain LU3 recorded the best results. The isolate of the Bacillus licheniformis strain CC91 was tested in the process of sealing fractures and openings with high permeability for samples of oil reservoir rocks.