Abstract
The present work aimed to optimize a molasses and tuna-processing by-products based new economic medium for biosurfactant (BS) production by a promising strain of Aneurinibacillus migulanus. A culture medium based on a mixture of molasses and supernatants generated from tuna by-products supplemented with oligoelements solution was optimized using the mixture design methodology. Biosurfactant (BS) production and emulsification index (E24) were evaluated. Maximal BS of 2.95 g/l was obtained with a 95:5 (v:v) mixture of molasses and tuna by-product supernatant. However, higher level of E24 (62%) was recorded with medium containing the proportion 5:95 (v:v) of molasses and tuna by-product supernatant. The predicted responses from these mixture proportions were also validated experimentally. Interestingly, oligoelements supplements were not needed to prepare the culture medium. Molasses and tuna-by-product, non-conventional substrates, can be used efficiently for BS production by A. migulanus.
Highlights
Surfactants are amphipathic molecules with hydrophilic and hydrophobic regions
A mixture design was applied to determine the optimum conditions for BS productions and to maximize the E24 by A. migulanus growing on media based on molasses supplemented with supernatant generated from boiled tuna by-product and with oligoelements
Fish by-product, which are an available substrates generated in large amount by the Tunisian industries, provide an excellent source for microbial growth media, which can be exploited in producing various high added value metabolites (Ben Rebah and Miled, 2013). The integration of both molasses and tuna-by-product in microbial growth media for BS production, can lower the bioprocess cost and reduce environmental problems associated with agro-waste materials and propose another environmental friendly disposal way
Summary
Surfactants are amphipathic molecules with hydrophilic and hydrophobic regions. These molecules can reduce surface tension at the air-water interface between two immiscible liquids or between the solid-water interfaces. The currently used surfactants are generally chemically synthetic or derived from petroleum like alkylbenzene sulfonate, quaternary ammonium chloride, salt of long chain amine, sulfobetaine and polyoxyethylenated alkylphenol (Rosen and Kunjappu, 2012) These chemicals are often toxic and non-biodegradable, representing an additional source of contamination (Reis et al, 2013). The hydrophilic portion, which is more soluble in water, can be a carbohydrate, amino acid, cyclic peptide, phosphate, carboxylic acid or alcohol (Chayabutra et al, 2001; Chen et al, 2007; Volchenko et al, 2007) These molecules reduce surface and interfacial tensions in both aqueous solutions and hydrocarbon mixtures, which makes them potential candidates in various sectors as cited above such as the bioremediation processes (enhance oil recovery from wells, reduce the heavy oil viscosity, clean oil storage tanks, increase flow though pipelines, stabilize fuel water-oil emulsions, etc.) (Mulligan, 2005). Molasses and tuna-by-product based-growth media supplemented with oligoelements were optimized for BS production by A. migulanus using mixture design methodology
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