In situ product recovery (ISPR), in the form of an extractive fermentation process, can increase productivity and product titers in the sustainable production of platform chemicals. To establish a guideline for the development of industrially relevant production processes for such bio-based compounds, a wide screening was performed, mapping the potential of an extensive range of solvents and solvent mixtures. Besides solvent biocompatibility with Saccharomyces cerevisiae, distribution coefficients of three organic acids (protocatechuic acid, adipic acid and para-aminobenzoic acid) and four fragrance compounds (2-phenylethanol, geraniol, trans-cinnamaldehyde and β-ionone) were determined. While for highly hydrophobic fragrance compounds, multiple pure solvents were identified that were able to extract more than 98%, reactive extraction mixtures were proven effective for more challenging compounds including organic acids and hydrophilic alcohols. For example, a reactive mixture consisting of 12.5% of the extractant CYTOP 503 in canola oil was found to be biocompatible and showed superior extraction efficiency for the challenging compounds as compared to any biocompatible single solvent. This mapping of biocompatible solvents and solvent mixtures for the extraction of various classes of industrial platform chemicals can be a tremendous step forward in the development of extractive fermentations.

This study investigates enzymatic hydrolysis of four novel polyesters (REPolymers) with different structures based on terephthalic acid, ethylene glycol, glutaric acid, and decanediol. These polyesters were synthesized from PET building blocks and bio-based monomers. A hydrolase from Rhizobacter sp. (Rhb), identified from a wastewater treatment sludge metagenome, was used to predict biodegradation and to assess enzymatic recycling potential of the REPolymers. Rhb shows homology to Ideonella sakaiensis PETase but exhibits superior thermostability and activity due to specific amino acids previously identified in PETase engineering. Using mass spectrometry and HPLC-DAD analysis, hydrolysis of REPolymers (5 - 34 kDa) was mechanistically studied. Mono-(2-hydroxyethyl) terephthalic acid (MHET) was the primary product, with longer PET oligomers and aliphatic dimers also detected, indicating endo-wise cleavage of aromatic and aliphatic ester bonds. Consistent degradation patterns showed dimer accumulation across different REPolymers. These findings illuminate how the polyester structure affects enzymatic hydrolysis, supporting the development of novel waste/bio-based polymers and recycling strategies.