A novel rhamnolipid-producing Pseudomonas aeruginosa ZS1 isolate derived from petroleum sludge suitable for bioremediation

Tao Cheng,Zhiwei Ge,Jibei Liang,Xingcui Hu,Jing He,Jianhua Liu

doi:10.1186/s13568-017-0418-x

Abstract

Petroleum pollutants emulsified by biosurfactants facilitate uptake and biodegradation by environmental microbes. In this report, we show the characterization of an indigenous surfactant-producing crude-oil-eating microbe isolated from petroleum-sludge in Zhoushan islands, China, where one of the national strategic petroleum reservoirs is located. We examined biosurfactant activities using surface tension analysis on mixed culture originated from oil-sludge microbes. In parallel, dynamics of individual microbial populations in cultures were monitored using the terminal fluorescence labeled (TFL)-RFLP method. Biosurfactant activity was found to be associated with a dominant microbial species designated as ZS1 (Zhou-Shan isolate 1). Cell-free supernatant from the ZS1 culture exhibited 100% emulsification index against crude oil and reduces surface tension to 26.5 mN/m. Sequence-based analysis suggested that the ZS1 belongs to the group of Pseudomonas aeruginosa. LC–MS/MS analysis indicated that the rhamnolipids produced by the ZS1 consisted of 7 monorhamnolipid and 11 dirhamnolipid homologues (RL7-11), two of which were novel. Maximum yield of rhamnolipids in shake-flask ZS1 culture could reach 44 g/l. Furthermore, we showed that ZS1 was capable of growing in MS medium supplemented with 1% crude oil as sole carbon source, in which cell mass increase coincided with the formation of crude-oil emulsion. Half of the crude oil was consumed by the ZS1 in 12 days. Taken together, our results show that ZS1 produces high level of rhamnolipids that effectively emulsify crude oil accelerating its uptake and degradation. Hence, it is suitable for bioremediation of petroleum pollutants in Zhoushan coastal areas.

Highlights

Petroleum leaks and spills are often linked to accidents resulting from activities related to the petrochemical industry involving oil drilling rigs, transportation tankers and pipelines, and storage reservoirs (Holliger et al 1997)
We describe a terminal fluorescence labeled (TFL)-RFLP-mediated screening method, from which we obtained a rhamnolipid-producing P. aeruginosa ZS1 isolate originated from petroleum sludge in Zhoushan islands
Isolation of glucose‐enriched biosurfactant‐producing microbes derived from oil sludge Petroleum sludge was collected near the Sanjiang Ferry Terminal located in Zhoushan islands, Zhejiang Province, China

Summary

Introduction

Petroleum leaks and spills are often linked to accidents resulting from activities related to the petrochemical industry involving oil drilling rigs, transportation tankers and pipelines, and storage reservoirs (Holliger et al 1997). Biosurfactants are surface-active amphiphilic compounds produced by living cells and provide a promising alterative to chemically synthesized surfactants, since they are low toxicity, high biodegradability, and. A number of microorganisms have shown to produce biosurfactants, for example, Acinetobacter calcoaceticus, Bacillus subtilis, Pseudomonas aeruginosa, and Starmerella bombicola produce emulsan, surfactin, rhamnolipids, and sophorolipids, respectively (Cooper et al 1981; Shoham et al 1983; Sponza and Gök 2010; Zajic and Supplison 1972). The most abundant species of rhamnolipids produced by P. aeruginosa are monorhamnolipids α-l-rhamnopyranosylβ-hydroxydecanoyl-β-hydroxydecanoate (rha-C10-C10) and α-l-rhamnopyranosyl-β-hydroxydecanoate (rha-C10) and dirhamnolipids α-l-rhamnopyranosyl-α-l-rhamno pyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (rha-rhaC10-C10) and α-l-rhamnopyranosyl-α-l-rhamnopyrano syl-β-hydroxydecanoate (rha-rha-C10) (Abdel-Mawgoud et al 2010)

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