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This study presents a novel and dynamic strategy to enhance rhamnolipid and sophorolipid production using isolated Pseudomonas aeruginosa and Starmerella bombicola, respectively, from an Egyptian oil field. The optimum productivity of rhamnolipid and sophorolipid was observed when 1% of crude oil was used as a carbon source at pH 6 and 3 and temperatures of 30 and 40 °C, respectively. The developed fed-batch cultivation strategy enhanced rhamnolipid and sophorolipid production by 1.4-and 1.96-fold, respectively. A robust complex consisting of the produced biosurfactants separately binding with t-octylphenoxypolyethoxyethanol was examined for enhancing oil recovery. The interfacial tension was reduced from ∼11.83 to ∼0.13 mN/m, and the wettability was modified from the common water-wet state [θ = ∼75−80°] to an excellent water-wet state [θ = ∼14.03−21.71°]. The core-flooding tests showed that the oil recovery process was enhanced for rhamnolipid and sophorolipid complexes by 66.07 and 55.63%, respectively.

In this work, we prepared nonionic surfactants from waste cooking oil materials. Hydrolysis was carried out for palm and palm kernel waste cooking oils to get a mixture of free fatty acids. The mixture of free acids was esterified with sorbitan and then ethoxylated at different ethylene oxide units. Two surfactants exhibited promising surface-active properties among the six prepared surfactants based on the results of surface tension. The interfacial tension (IFT) around the critical micelle concentration was measured against a series of n-hydrocarbon to detect the minimum alkane carbon number (ACN) (Πmin) for each of these surfactants. The effect of normal and branched alcohols on Πmin was also studied to design the surfactant/alcohol mixture for the chemical flooding process. From the results of IFT, the ethoxylated ester derivatives of palm kernel fatty acids (EPK-20) exhibited minimum IFT γmin (0.06 mN m–1) at Πmin equal to 12, and the ethoxylated ester derivatives of palm fatty acids (EP-40) achieved γmin equal to 0.09 mN m–1 at Πmin of 10. Branched alcohols shifted Πmin to a higher value to reach the equivalent ACN of the crude oil and decrease the IFT to lower values. The flooding process showed that the maximum oil recovery was obtained by EPK-20 (54.2% when used purely and 66.2% when used with isoamyl alcohol). In comparison, EP-40 exhibited that oil recovery equals 46% without alcohol and 46.4% with iso-butanol alcohol. The results were interpreted and discussed based on interfacial properties, wettability alteration, and the ACN.

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Oil spill contamination in soil is still problematic. At the same time, petroleum-contaminated soil in oil reservoirs contain various microbes, which have the ability for biosurfactant production. Extracting these biosurfactants is a very promising and cost-effective strategy for the microbial enhanced oil recovery process. Biosurfactants production using Bacillus licheniformis AnBa7 and Rhodococcus erythropolis sp., isolated from Egyptian crude oils, was enhanced using various carbon sources. The best biosurfactant characteristics were observed when 1% of crude oil was used as a carbon source. The production was further improved by using a developed fed-batch cultivation strategy depends on using 1% Glucose as a single addition at the beginning of the culture. Then 1% of crude oil was added three times during the production process. This strategy enhanced surfactin and trehalose productivity by 1.8 and 4.7 fold higher than the normal conditions, respectively. The surface-active and thermodynamic properties were studied. The results indicated that the calculated values of ΔG mic for surfactin complex, and trehalose complex were −18.47 and −18.28 kJ/mol at 60 °C, respectively while ΔG ads values were −30.42 and −29.46 kJ/mol at 60 °C. The interfacial tension (IFT) values of surfactin complex and trehalose complex systems were ranging from 0.75 to 0.19 mN m −1 and from 0.93 to 0.26 mN m −1 at 60 °C, respectively. However, the (IFT) for the blank solution was ∼11.57 mN m −1 , and the wettability was changed to an excellent water-wet state (θ = ∼ 17.42−24.0°). The core-flooding studies showed that the enhanced oil recovery for surfactin complex and trehalos complex, at maximum concentration 6 g/L, were 59.21% and 51.83%, respectively. A predicted mechanism was illustrating through the text.