A systematic selection of the non-aqueous phase in a bacterial two liquid phase bioreactor treating α-pinene

A systematic evaluation of the selection criteria of non-aqueous phases in two liquid phase bioreactors (TLPBs), also named two-phase partitioning bioreactors (TPPBs), was carried out using the biodegradation of alpha-pinene by Pseudomonas fluorescens NCIMB 11671 as a model process. A preliminary solvent screening was thus carried out among the most common non-aqueous phases reported in literature for volatile organic contaminants biodegradation in TLPBs: silicon oil, paraffin oil, hexadecane, diethyl sebacate, dibutyl-phtalate, FC 40, 1,1,1,3,5,5,5-heptamethyltrisiloxane (HMS), and 2,2,4,4,6,8,8-heptamethylnonane (HMN). FC 40, silicone oil, HMS, and HMN were first selected based on its biocompatibility, resistance to microbial attack, and alpha-pinene mass transport characteristics. FC 40, HMS, HMN, and silicone oil at 10% (v/v) enhanced alpha-pinene mass transport from the gas to the liquid phase by a factor of 3.8, 14.8, 11.4, and 8.6, respectively, compared to a single-phase aqueous system. FC 40 and HMN were finally compared for their ability to enhance alpha-pinene biodegradation in a mechanically agitated bioreactor. The use of FC 40 or HMN (both at 10% v/v) sustained non-steady state removal efficiencies (RE) and elimination capacities (EC) approximately 7 and 12 times higher than those achieved in the system without an organic phase, respectively. In addition, preliminary results showed that P fluorescens could uptake and mineralize alpha-pinene directly from the non aqueous phase.