Modelling and optimisation of gas-liquid mass transfer in a microporous hollow fiber membrane aerated bioreactor used to produce surfactin

[Display omitted] •An approach coupling DA and DOE is proposed to model membrane-aerated bioreactors.•Effects of liquid flow rate, volume, gas pressure and surface tension are explored.•Process relationships to predict aeration performances are proposed.•Scaling-up of such bioreactor performances are discussed, guidelines are proposed. Aeration by a membrane contactor is a convenient method to produce surfactin, a bacterial surfactant compound, while avoiding foam to overflow as it is the case with most of aerated bioreactors equipped with gas sparger. This work helps improving knowledge on oxygen transfer in membrane-aerated bioreactors and optimizing the adjustment of culture aeration performances. In this work, oxygenation of a surfactin solution was studied in a bioreactor aerated by a microporous hollow fiber membrane contactor. First, a dimensional analysis was coupled in an innovative way with a fractional design of experiments, thus reducing greatly the number of experiments. Then, the analysis of the model helped to understand thoroughly the influence of the four main parameters, namely the liquid flow rate inside the fibers, the gas pressure outside the fibers, the liquid volume in the tank and the amount of surfactant in the bulk. Empirical process relationships were proposed to predict either the volumetric oxygen transfer coefficient (kLa) or the liquid-side oxygen transfer coefficient (kL) (with an average standard deviation < 11%). The liquid flow rate, the liquid volume and the gas pressure were found to be significantly influencing unlike the surface tension. The validity of the relationships with surfactin fermentations obtained at a larger scale was demonstrated.