Efficient conversion of black cumin cake from industrial waste into lipopeptide biosurfactant by Pseudomonas fluorescens

Abstract

Most biosurfactants are obtained using costly culture media, which limits their wider industrial use. In the present study, a low-cost culture medium, containing the agro-industrial residue black cumin cake, was developed for amphisin production by Pseudomonas fluorescens DSS73. By using black cumin cake as the substrate, not only was the production cost reduced but also a higher production yield was achieved. A Box-Behnken experimental design was applied to maximize lipopeptide biosurfactant production. The optimal conditions for amphisin production, such as black cumin cake (6.6%) and NaCl (8.0 mM) concentration, and cultivation time (6.5 days), were determined. Yield of amphisin production, performed in optimal conditions, reached 16.51 ± 0.49 g/L. Such high production has not been evidenced previously for Pseudomonas lipopeptide biosurfactants. Moreover, active utilization of the substrate, observed with the aid of scanning electron microscopy (SEM), documented by numerous holes and pitting on the black cumin cake surface, was confirmed. Finally, antifungal activity of amphisin against Aspergillus carbonarius was demonstrated. Hence, amphisin production by P. fluorescens was achieved with statistical optimization using an inexpensive agro-industrial by-product for the first time.