Factorial designs are accurate tools to pick up the most promising extremophiles for future biosurfactant production.

In this study, five strains previously isolated from black liquor (BL) and vinasse (V) were tested to assess the most promising regarding its capacity of biosurfactant production. For that, four factorial designs of two factors at two levels (2 ² ) were run for each strain. Selected factors were the production time and the composition media, while the surface tension reduction and optical density were the responses variables. Production media prepared just with V or BL exhibited minimal biosurfactant production, while better results were achieved when media were formulated with nutrient broth (NB), olive oil (Oo), and a percentage of V or BL. Result showed that Bacillus sp. b1 reported the highest surface tension reduction (29.39 mN/m and OD = 8.7) using 5 % BL, 5 g/l NB and 11.5 g/l Oo during 2 to 4 days followed by Lactobacillus sp. a1 (19.47 mN/m and OD = 10.87) using 1 % V, 1 g/l NB and 2.5 g/l Oo during 2 to 4 days. The other strains also showed promising results (Alkalihalobacillus sp. b2: 16.91 mN/m; Pichia sp. a6: 13.8 mN/m; Lactobacillus sp. a5: 13.66 mN/m). This study provides crucial insights regarding the ability of these particular extremophiles strains of producing biosurfactants with the hope of optimizing the process and be able to scale up the production. This will be a huge step towards the development of environmentally friendly bioproduct which can eventually compete with synthetic surfactants.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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