Optimizing alternative substrate for simultaneous production of surfactin and 2,3-butanediol by Bacillus subtilis LB5a

Biotechnological processes, such as the production of enzymes, peptides, bioflavours, biosurfactants, etc., are increasing, worldwide. Bacillus subtilis synthesizes surfactin, a powerful surface-active agent. However, due to its high production cost, commercial use is impractical. In this sense, the culture medium of biosurfactants represents ≈30% of cost of production. Another interesting compound produced by B. subtilis is 2,3-butanediol, which has potential application in rubber, fuel, etc. Thus, the main aim of this work was to optimize the simultaneous production of surfactin and 2,3-butanediol by Bacillus subtilis LB5a using alternative substrates, in which the production of 2,3-butanediol was evaluated by both by solid-phase microextraction and liquid-liquid extraction. In addition, as secondary aim, it was evaluated the biofilm formation by Bacillus subtilis on activated carbon, which may improve the production of surfactin. The experiments of central composite design indicated that the best substrate composition for both bioproducts is whey (27.7–34 g/L), activated carbon (25 g/L) and cassava wastewater (74 g/L). The bioprocessing at bench-top scale achieved the simultaneous production of ≈27.07 mg/L of surfactin and ≈330 mg/L of 2,3-BD (SPME plus liquid-liquid extraction). These results proved the technical feasibility of an interesting strategy of biotechnological production (simultaneous) using alternative substrates. The identification of clusters also leads to a prospecting studies on the separation of each cluster and further evaluation of their surface-active properties.