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    • The current used bacterial strain i e Burkholderia sp C

    2020-08-06

    The current used bacterial strain, i.e. Burkholderia sp. C3, was isolated from PAH contaminated soil. It was formerly endorsed that for the bioremediation of oil spills contaminated locations, it is advisable to screen and isolate the situated microbial producers of biosurfactants. In these contaminated sites, which mostly could produce a mixture of 1–2 rhamnose parts connected with 1–2 chains from β-hydroxy fatty acid, with average carbons length of 8–12, the decanoic HPF (C10) is the most abundant (Ron and Rosenberg, 2001). The MS indicated that carbon source could influence the quantity and structures of biosurfactants; RLs could be generated as different mixtures of congeners with more than 28 currently known structural homologs. Cultivated P. aeruginosa, on glycerol, could produce a mixture composite of 10 congeners with 1–2 rhamnoses associated to 3 hydroxy fatty acids; the predominant was Rha-Rha-C10-C10 then Rha-C10-C10, as a result of hexadecane utilization (Deziel et al., 1999). Even minor alterations in the surfactants structure could have consequences on their physico-chemical characteristics; mono-RLs have less solubility, stronger surfaces sorb, and stronger cationic metals binding than homologue di-RLs (Zhang et al., 1997). The HPLC separation of RLs structure is based on their polarity. Purified biosurfactant that produced from the different diesel sources, in the current study, was eluted using HPLC. HPLC was recommended as an excellent tool for rhamnolipids separation (Aguilar, 2004). RLs could also be detected with various tools; the UV absorbance and chromatography on a C-18 column were applied for detecting the structure of crude RLs, dissolved in 30% methanol (Gueldner et al., 2003), whereas Romero et al. (2007) could analyze the RLs using TLC method than by analytical C-18 column in the RP-HPLC. Data obtained from MALDI-TOF-MS analysis of produced RLs, from biodiesel S, showed well-resolved peaks groups at m/z values of 527.281, 673.290, 761.310 and 717.269. The mass peaks at 527.281, 673.290 and 717.269 indicated structural homogenous RLs (Rha C10-C10), while structural RLs in a mass peak at 673.290 and 717.269 m/z could be attributed to non-homogenous RLs (Rha C10-C12). In addition, the mass peaks at m/z 717.269 indicated rhamnolipids with a mixture of structural analogs such as (Rha C14-C16) and the unique and new structure homogenous rhamnolipids Rha C16-C16. While the RLs (Rha C12-C14) was detected at 673.290. Mass spectrometry confirmed isomers of rhamnolipids in purified fractions containing a β-hydroxy fatty acid with Rha-Rha-C12-C12 and Rha-Rha-C12-C14 at the same peak 761.310.
    Conclusions Rhamnolipid production by Burkholderia sp. C3 could be successfully achieved from basal minimal medium supplemented with hydrocarbons raw materials, e.g. petro-diesel, biodiesel S and BP diesel B20. The supplementation with diesel and biodiesel greatly enhanced RLs production. The specific analysis of produced RLs indicated their containments of different rhamnolipidic congeners’ mixture (mono-rhamno-mono-lipidic, mono-rhamno-di-lipidic and di-rhamno-di-lipidic). Burkholderia sp. C3 could be promisingly recommended for the biodegradation of hydrocarbon wastes for the production of the valuable RL mixtures.