In-situ product recovery is a method for alleviating product inhibition in white biotechnology. Removing products from the fermentation broth can result in higher carbon yields, higher volumetric productivities and longer fermentation running times. However, there is still a lack of highly selective recovery techniques with a high capacity in the field of fermentations. A new tool in the field of integrated bio-processes are so-called solvent impregnated resins (SIRs). SIRs are particles that contain a selective solvent inside their polymeric matrix. SIRs have been applied in-situ to remove phenol from fermentation broths effectively.

Novel capsules

Recently, novel capsules were developed with several favourable characteristics compared to SIRs. Due to their larger radii and higher void volume, the capsules have superior solvent capacities. The solvent volume fraction in the particles was increased from 0.5 in SIRs to 0.88 in capsules, significantly increasing the amount of product that could be extracted per volume of particle. However, due to the larger radii of the capsules, mass transfer rate is somewhat slower compared to the SIRs.

Impact of product recovery on fermentation

In order to maximize volumetric productivity and product yield on carbon source, product concentrations have to remain low in fermentations. A balance has to be made between microbial productivity, down-times and product flux into SIRs or capsules. The influence of in-situ product recovery on fermentation efficiency using these particles is evaluated by comparing 3 typical bio-chemical product cases with different toxicities, productivities, glucose yields and organic phase partitioning behaviour.