Biosurfactant production by Trametes versicolor grown on two-phase olive mill waste in solid-state fermentation

Biosurfactants are amphiphilic compounds of microbial origin which exhibit better properties than their chemically derived counterparts. They are usually produced in submerged fermentation by different types of bacteria. However, biosurfactant production by fungi, particularly of the white-rot type, has been scarcely studied. In this work, and for the first time, we report the production of biosurfactants by the white-rot fungus Trametes versicolor, which was grown on two-phase olive mill waste (TPOMW) in a solid-state fermentation system. The effect of the composition of the culture medium on biosurfactant production was also studied. The highest biosurfactant production (373.6 ± 19.4 mg in 100 g of culture medium) was achieved with a medium containing 35% (w/w) of TPOMW, the highest concentration used, 10% of wheat bran and 55% of olive stones. Interestingly, no inhibition of biosurfactant production by TPOMW was detected within the concentration range used (5-35% w/w). The biosurfactant produced by T. versicolor was able to reduce the surface tension of an aqueous extract of the culture medium up to 34.5 ± 0.3 mN m^-1. A preliminary study of the chemical structure of the biosurfactant indicated that it contains both lipid and protein fractions. The simultaneous production of lignin-degrading enzymes was also assessed.