High throughput screening of the potential biosurfactants production by extremophiles isolated from vinasse and black liquor

Abstract

The aims of this work were to isolate microorganisms from vinasse (V) and black liquor (BL), by-products of alcohol and paper industries and to assess their potential as substrates to produce biosurfactants. Thirty-nine microorganisms, 19 from V (acidophilic, a1 to a19) and 20 from BL (alkaliphilic, b1 to b20) were isolated. A high- throughput method was design and set up for surface tension (γ) measurement. In the first screening, 15/39 strains were pre-selected for their capacity of γ reduction of media formulated with V and BL. A Student's t-test was applied to data obtained in the second screening, to search for significant differences among γ values reached in each production media and their respective sterile medium. Three acidophilic (a1, a5, a6) and 3 alkaliphilic (b1, b2, b17) significantly decreased the γ compared to the control (p < 0.05) after 5 days with 5% of substrate concentration. A BCindex was defined to assess biosurfactant capacity. The strains showed the following percentage of γ reduction: Lactobacillus rhamnosus a5 (34%), Bacillus safensis b1 (13%), Alkalihalobacillus halodurans b2 (10%) and Pichia cecembensis a6 (10%), Lactobacillus paracasei a1 (6%). The two strains that presented the best potential biosurfactant capacity and the greatest γ reduction when compared to the control (p-value) were Lactobacillus rhamnosus a5 (BCindex = 16.98, p = 0.007), and Bacillus safensis b1 (BCindex = 17.66, p = 0.003). These industrial by-products are a source of new super-producing strains and will be assess as economic substrates for biosurfactant production.