Optimization of Bacillus subtilis SPB1 Biosurfactant Production Under Solid-state Fermentation Using By-products of a Traditional Olive Mill Factory

AbstractBacillus subtilis SPB1 is known to produce a highly effective biosurfactant that belongs to the class of lipopeptides. This biosurfactant has shown relevant properties that could be efficiently applied in various domains. However, high production and purification costs limit the use of B. subtilis SPB1 in high-volume applications. The present work aimed to promote an economical production of this lipopeptide biosurfactant. Statistical experimental designs and response surface methodology were employed to optimize the concentrations of agro-industrial residues, inoculum size and humidity for B. subtilis SPB1 biosurfactant production under solid-state fermentation. The best production yield was approximately 30.67mg of crude lipopeptide biosurfactant per gram of solid material. This yield was obtained using a solid substrate ratio of 1.5, a moisture content of 90% and an inoculum size (OD600) of 0.08. These data support the utilization of a mixture of 6g of olive leaf residue flour and 4g of olive cake flour with a 10g total weight of the solid substrate. A mixture of two by-products of a traditional olive mill factory was demonstrated to be a suitable substrate for biosurfactant biosynthesis, providing enhanced bacterial growth and leading to a strong improvement in the yield of tensioactive lipopeptide production