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. 2025 Jan 10;11(2):e41877.
doi: 10.1016/j.heliyon.2025.e41877. eCollection 2025 Jan 30.

Biodesulfurization of high-sulfur oil from the Karazhanbas field of Kazakhstan with deep eutectic solvents

A O Akimbek  1 , G A Jamalova  2   1 , A K Yernazarova  3 , G K Kaiyrmanova  3 , B K Yelikbayev  1 , M C Pagano  4 , A G Zazybin  5 , Kh S Rafikova  1
Affiliations

Biodesulfurization of high-sulfur oil from the Karazhanbas field of Kazakhstan with deep eutectic solvents

A O Akimbek et al. Heliyon. .

Abstract

The Karazhanbas oil field in the Mangystau region of Kazakhstan contains high-sulfur oil (1.6-2.2 %). It is known that sulfur negatively affects the operational properties of petroleum products, causes the corrosion of pipelines, and adversely affects the environment and the human body. Therefore, the development of biodesulfurization technology, taking into account local features, is relevant for this field. The purpose of the study is to develop biodesulfurization of high-sulfur oil from the Karazhanbas field in Kazakhstan using deep eutectic solvents. Research objectives: isolation of sulfate-oxidizing and sulfate-reducing bacteria from the studied oils; identification of isolated bacteria; study of the effect of heavy metal Cr(VI) and sulfur on microbial activity; testing of native strains for the potential for desulfurization of crude oil. The research methodology was based on the application of the Koch methods to determine the total number of microorganisms; light microscopy - for the study of microbiological preparations; genetic identification of bacteria based on the analysis of the nucleotide sequence of a fragment of the 16S rRNA gene; synthesis of deep eutectic solvents; testing of isolated bacteria - for sensitivity to Cr (VI), for the ability of microorganisms to use hydrocarbons of high-sulfur oil, for activity in sulfur-containing crude oil, for determination of the mass fraction of sulfur. From 12 aerobic bacterial cultures isolated from oil samples, 9 strains with active and moderate growth in a medium with high-sulfur oil were selected during testing, followed by two strains (Bacillus paramycoides SFN-1, Bacillus cereus SFN-2), which were the most resistant to Cr (VI) and two strains (Bacillus cereus SFN2, Bacillus thuringiensis SFN3), which have shown sulfur-oxidizing abilities. The native bacterial strains selected during the study showed high disulfurization activity without the addition of deep eutectic solvents (hereinafter referred to as DES) (Bacillus thuringiensis SFN3), with the addition of DES-1 (Bacillus cereus SFN2) and with the addition of DES-2 (Bacillus thuringiensis SFN3). As a result of a comparative analysis of microbial desulfurization processes, it was found that the highest biodesulfurization rate at the end of the experiment was recorded in cultures of Pseudomonas aeruginosa B-5807 (96.3 %), Bacillus thuringiensis SFN-3 (96.1 %), and Rhodococcus erythropolis AC 1039 (96 %).

Keywords: Biodesulfurization; Deep eutectic solvents; Heavy metals; Karazhanbas deposit; Mass fraction of sulfur; Sulfur oxidation; Sulfur reduction.

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Conflict of interest statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Khadichakhan Rafikova reports financial support was provided by K. I. Satbayev Kazakh National Research Technical University. Khadichakhan Rafikova reports a relationship with Satbayev University that includes: employment. Khadichakhan Rafikova has patent - pending to -. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Micromorphology of isolated bacterial cultures. a) SFN1; b) H2; c) H1; d) H5. The photos were taken with the SOPTOP EX330 at the magnification of 1000×.
Fig. 2
Fig. 2
Determination of bacteria capable of active growth in a medium with high-sulfur oil a) abundant growth was noted for strains H1, H2, and H4, b) moderate growth was observed for strains F1, E1, and F2.
Fig. 3
Fig. 3
Phylogenetic tree based on the analysis of the 16S rRNA gene fragment of SFN1, SFN2, SFN3, H1, H4, H2, F1, F2, E1 samples.
Fig. 3
Fig. 3
Phylogenetic tree based on the analysis of the 16S rRNA gene fragment of SFN1, SFN2, SFN3, H1, H4, H2, F1, F2, E1 samples.
Fig. 4
Fig. 4
Dynamics of changes in optical density (units) during the cultivation of bacteria on BCH with the addition of Cr (VI), Dopt (experiment) and without Cr (VI), Dopt (control). a) Bacillus paramycoides SFN-1 b) Bacillus cereus SFN-2, c) Bacillus thuringiensis SFN-3, d) Bacillus subtilis H-1, e) Bacillus siamensis Н-4, f) Bacillus haynesii F-1, g) Bacillus zhangzhouensis F-2, h) Peribacillus simplex Е-1, i) Microbacterium sp. Н-2.
Fig. 4
Fig. 4
Dynamics of changes in optical density (units) during the cultivation of bacteria on BCH with the addition of Cr (VI), Dopt (experiment) and without Cr (VI), Dopt (control). a) Bacillus paramycoides SFN-1 b) Bacillus cereus SFN-2, c) Bacillus thuringiensis SFN-3, d) Bacillus subtilis H-1, e) Bacillus siamensis Н-4, f) Bacillus haynesii F-1, g) Bacillus zhangzhouensis F-2, h) Peribacillus simplex Е-1, i) Microbacterium sp. Н-2.
Fig. 5
Fig. 5
Growth of microorganisms in a medium with high-sulfur oil, CFU/ml.
Fig. 6
Fig. 6
Growth of microorganisms in a medium with high-sulfur oil, CFU/ml.
Fig. 7
Fig. 7
Growth of microorganisms in a medium with high-sulfur oil with the addition of DES-1 (2 %), CFU/ml.
Fig. 8
Fig. 8
Growth of microorganisms in a medium with high-sulfur oil with the addition of DES- 2 (2 %), CFU/ml.
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