Experimental Investigation of Sophorolipid Biosurfactants Produced by Candida and Pleurotus Species Using Waste Oils and Rice Bran and Their Oilfield Benefits

E Ahuekwe,O Stanley,B Okoli,B Kinigoma

doi:10.9734/jabb/2016/27467

E Ahuekwe, O Stanley + Show 2 more

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https://doi.org/10.9734/jabb/2016/27467

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Abstract

Conventional chemical surfactants applications usually linked with environmental unfriendliness and toxicity are associated with high production costs resulting from fluctuations in oil prices and thermal energy requirements. Sophorolipid biosurfactants can potentially be implemented with a remarkably low operating cost. Besides economic interest, sophorolipids and their derivatives have shown promise as emulsifiers, antimicrobials, surfactants and a source of specialty chemicals reduction capacities, thus, facilitating microbial hydrocarbon and heavy metal emulsification and uptake. In this study, sophorolipids produced by Candida and Pleurotus species respectively isolated and harvested from oil contaminated soils from Ukwa West LGA of Abia State were investigated. Mineral salt media supplemented with different hydrophilic (rice bran, spent mushroom substrate and cassava peels) and hydrophobic (food industry waste oil) renewable wastes as sources of carbon were tested on nine (9) of the potential isolates to select the best medium and organism that maximized sophorolipids production. This was supported by the emulsification index after 24 hours (E24), FT-IR and GC-MS analysis. All isolates were subjected to biosurfactants production screening, to find the best sophorolipid producer among the available strains. Results showed that isolate CP1SP6c, a hydrocarbon utilizing fungi (HUF) exhibiting β- haemolysis and 92.4% microbial adhesion to hydrocarbon (MATH), gave the maximum E24 of 69.2%, within 6 days of incubation on media fortified with rice bran and food industry waste oil in a rotary shaker. Further studies on CP1SP6c were carried out to assess the interaction of the produced sophorolipids with porous media in core flooding experiments as a tertiary recovery technique. The results showed high promises of using this bio-product in hydrocarbon recovery, where 12.3% of crude oil was recovered after injecting the culture supernatant. An additional recovery of 15.7% of residual oil was observed after concentrating the sophorolipid solution.

Highlights

IntroductionBiosurfactants are valuable microbial amphiphilic compounds with effective surface active and biological properties applicable to several industries and process materials
The results showed high promises of using this bio-product in hydrocarbon recovery, where 12.3% of crude oil was recovered after injecting the culture supernatant
This study reports the best substrates for the production of sophorolipid biosurfactants and the ability of these fungal isolates to produce large amounts of sophorolipids on water-immiscible waste oils and water-soluble substrates at a laboratory scale

Summary

Introduction

Biosurfactants are valuable microbial amphiphilic compounds with effective surface active and biological properties applicable to several industries and process materials Owing to their superior properties of diversity, higher biodegradability, ecological acceptability and production from wide range of raw materials over petroleum-based surfactants, interests in their use in various industrial applications has increased [1,2]. Surfactants possess both hydrophilic and hydrophobic structural moieties, which impart many unusual properties, including an ability to lower the surface tension, facilitating hydrocarbon emulsification and uptake [3,4]. Other potential applications of biosurfactants relate to the pharmaceutical, cosmetic and food processing industries [9]

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