Mass Transfer Enhancement by the Addition of Surfactant in a Two Phase Partitioning Bioreactor for the Degradation of Anthracene by Laccase

Abstract

A Two Phase Partitioning Bioreactor (TPPB) was proposed to carry out the degradation of the poorly soluble compound anthracene by laccase from Trametes versicolor. The organic phase consisted of silicone oil saturated with anthracene. The surfactant (Triton X-100) was added to the aqueous phase at concentration above the critical micelle concentration (CMC) to enhance anthracene solubility. The feasibility of reusing the aqueous phase, containing the laccase-mediator system was tested in three consecutive cycles of 24 h with an initial laccase activity of 1200 U/L and 1 mM of the mediator 1-hydroxybenzotriazole (HBT). In the first cycle, total degradation of anthracene took place at a high conversion rate: 16 µmol/LRh. The degree of removal achieved in two subsequent cycles with no extra addition of laccase or HBT were 68 % and 40 % for a laccase activity of 150 and 90 U/L in each cycle respectively. These results proved the potential of a TPPB including a surfactant for the removal of poorly soluble compounds by the enzyme laccase and the possibility of exhausting the oxidative potential of the aqueous phase in consecutive cycles to minimize consumption of both laccase and the mediator.