Optimization, Stability assay and Application of Rhamnolipid biosurfactant produced by crude oil-degrading bacterium, Enterococcus hirae, isolated from diesel-contaminated soil

1*Ibukun Akinsanya Omore, 2Ibrahim Yusuf, 2Auwalu Halliru Arzai and 3Basiru Sulaimon

1MAF Environmental Consultancy, Lagos, Nigeria
2Department of Microbiology, Faculty of Life Science, Bayero University Kano, Kano, Nigeria.
3Africa Genome Centre, Mohammed VI Polytechnic University, Morocco.

Corresponding author: Omore, I. A., MAF Environmental Consultancy, Lagos, Nigeria.
*Corresponding author’s Email: mafec2741443@gmail.com, doi.org/10.55639/607.special.007


ABSTRACT

Crude oil spillage causes lots of disastrous environmental pollution. The employment biosurfactant-producing and hydrocarbon-utilizing microorganisms increase the bio-availability of petroleum hydrocarbons, thus enhancing the effectiveness of bioremediation. This study was aimed at optimizing the biosurfactant-production capability of Enterococcus hirae, testing the stability of the biosurfactant produced and applying the biosurfactant on emulsification of some hydrocarbons. The growth and biosurfactant production of the bacterium was optimized using one factor at a time on incubation temperature, incubation time, pH, additional carbon sources and nitrogen source. The biosurfactant was subjected to stability test on pH, temperature and salinity as well as being applied on different hydrocarbons to determine its emulsifying capability. The optimized conditions were determined as 30oC, pH 7.5, 120hours, Glycerol and Ammonium sulphate. The stability test showed that the biosurfactant retained its highest emulsifying activity of 57.58% at 40℃, 52.94% at pH 8 and 53.76% at 8% salinity. The biosurfactant showed the highest emulsifying activity against diesel (59%) and the lowest against petrol (50%). This study is the first to demonstrate E. hirae as an efficient biosurfactant producer with a production of 10.2g/L of biosurfactant using the optimized conditions. Furthermore, the biosurfactant produced was stable at different ranges of temperatures, pH and salinity as well as being effective in emulsifying some hydrocarbons. The stability of the biosurfactant approves its usage in bioremediation of oil spills and in microbial enhanced oil recovery (MEOR) as well as in other industri

Optimization,
Stability test,
E. hirae,
Glycerol.

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