Glycolipid biosurfactant production and petroleum hydrocarbon degradation by a new strain of Citricoccus zhacaiensis

Abstract

With the growth of the petroleum industry and its products, there has been a substantial increase in oil pollution. The intrinsic resistance of petroleum poses challenges in its total removal from the ecosystem. The identification and characterization of efficient biosurfactant-producing bacteria can help in environmental remediation. In the present study, a novel Citricoccus zhacaiensis strain, RP4, was identified and tested for hydrocarbon breakdown and biosurfactant synthesis. The phylogenetic tree of the isolated strain resembled Citricoccus zhacaiensis FS24 (99.26%) and Citricoccus parietis 02-Je-010 (99.10%). Bacteria exhibited 35.07 ± 7.25% cell-surface adherence to n-hexadecane, indicating hydrophobicity. The strain RP4 consumed 95% diesel, 99.94% kerosene, and 98.65% n-hexadecane in 14 days, demonstrating hydrocarbonoclastic potential, as confirmed by fluorescence microscopy. GC/MS analysis showed that the biosurfactant primarily contained hexadecenoic, octadecenoic, and octadecadienoic acids. Structural analysis utilising FTIR, NMR, and MALDI-TOF suggested a glycolipid-type biosurfactant. The biosurfactant was stable at 100 °C, 200 mg/l of salinity, and a pH range of 2–12. Biosurfactant had a CMC of 0.185 mg/ml and decreased distilled water surface tension to 33.38 mN/m. The glycolipid biosurfactant emulsified benzene, paraffin oil, and xylene by ≥ 80% at 0 h and ≥ 55% at 24 h. The study concludes that Citricoccus zhacaiensis RP4 could be exploited for bioremediation and glycolipid biosurfactant production. This study is the first to report biosurfactant production and petroleum hydrocarbon bioremediation by C. zhacaiensis.