Evaluation of ionic liquids as dispersed phase during the production of lactones with E. coli in a three phase partitioning bioreactor

•Conversion at inhibitory conditions was improved with the use of the IL.•Parameters (Kpp, Kps, ksA, kpA, kin, kLa) were used to select the most proper IL.•Cell viability was described using the power law equation model.•Cell viability was the main criteria to select the most proper IL.•[OMA][BTA] led to the lowest loss of cell viability (ca. 55%).

The aim of this work was to experimentally and theoretically evaluate the performance of four ionic liquids (ILs) used in the three-phase (air–water–IL) partitioning bioreactor (TPPB) for the production of bicyclic lactone (1S,5R)-2-oxabicyclo[3.3.0]oct-6-en-3-one from bicyclic ketone bicyclo[3.2.0]hept-2-en-6-one over Escherichia coli strain TOP10 pQR239. In particular, partition coefficients of the substrate and product, mass-transfer coefficients of the substrate, product and oxygen, as well as the deactivation parameters related to the loss of cell viability, owing to the presence of the IL, were determined. To the best of our knowledge, cell viability was described, for the first time, using a power law equation model. The operation of the biphasic system without inhibitory conditions led to a substrate conversion of 100%, whereas the conversion was approximately 25% under inhibitory conditions. Besides, when the IL was used as the dispersed phase in the TPPB, the substrate conversion under inhibitory conditions was between 20% and 85%. All evaluated ILs were thermodynamically suitable for use as the dispersed phase; however, all of them provoked a loss in cell viability. When trioctylmethylammonium bis (trifluoromethylsulfonyl)imide [OMA][BTA] was used in the three-phase system, the highest substrate conversion (ca. 85%) and the lowest loss of cell viability (ca. 55%) were observed, even though this IL presented lower partition coefficients for the substrate and product as well as the lowest oxygen, substrate and product mass-transfer coefficients compared to the other ILs under the studied operating conditions. These results indicate that the effect of the IL on the cell viability is an essential parameter that must be considered before the application of an IL in TPPB technology.