IMPRINTS

The dramatic increase of environmental disasters urges the scientific community to quickly find environmentally and economically viable alternatives to the current fossil-fuel based processes. In this tense context, the transition towards a bioproduction of platform molecules is of particular interest. These molecules indeed allow the production of a significant amount of products used on a daily basis. This transition however currently faces multiple scientific and technical challenges. The 3-hydroxypropionic acid, a positional isomer of lactic acid, is one of the most interesting platform molecules to be produced from biomass. This acid indeed allows the synthesis of a myriad of products such as acrylic acid. Research efforts therefore have to be made to bioproduce this acid. Biobased organic acid production often requires to couple bioproduction and continuous product extraction through a separation process. This coupling is known as ISPR (In-Stream, or In-Situ Product Recovery), and aims at limiting acid accumulation inside the conversion medium, in order to avoid product inhibition. Several studies clearly demonstrated the potential of 3-hydroxypropionic acid bioproduction. Its ISPR bioproduction with conventional extraction devices (liquid-liquid extraction in membrane contactors) however currently faces limitations. These limitations are related to the fact that bioproduction inside the fermenter is significantly faster than continuous extraction. This physical barrier therefore limits the production rates and scale-up capacities of this integrated bioprocess. In this context, the purpose of IMPRINTS is to use small-scale fluidics (milli and microfluidics) to tackle two main limitations currently found in acid organic bioproduction, through the case study of 3-hydroxypropionic acid. The first one is the lack of fundamental knowlegde on mass transfer occuring when performing reactive liquid-liquid extraction to recover the acid of interest from a fermentation broth. A broth is indeed composed of a multitude of components, that will impact reactive mass transfer. Microfluidics will therefore be used as a quick and reliable tool to elucidate and quantify mass transfer mechanisms occuring when extracting acid from a multicomponent medium. Microfluidics indeed allow to unravel these phenomena by perfectly controlling the hydrodynamics and surface exchange between the aqueous phase and extractant phase. This information is especially useful to perform an efficient dynamic bioproduction mechanistic modelling, that accounts for the influence of the broth. The second issue is related to the lower extraction performances observed when coupling bioproduction and separation. An innovative triphasic millifluidic process, combining extraction and back-extraction, will be developped to tackle this issue. This intensified process relies on the mass transfer enhancement occuring under multiphasic Taylor flow (aqueous droplets dispersed in the reactive organic phase, or membrane phase). This flow is well-known for highly intensifying mass transfer due to the association of recirculation vortices (inside and between the droplets) and high surface/volume ratios. A comprehensive dimensional analysis will be performed in parallel of the process development, thus offering all the needed tools for scale-up. This intensified extraction process will ultimately be coupled to a bioreactor in order to validate its performances in real working conditions. A dynamic mechanistic bioproduction-extraction model will ultimately be developped, that will allow to control, optimize, and scale-up the coupled process.