High-flux POMS organophilic pervaporation for ABE recovery applied in fed-batch and continuous set-ups

The performance of fed-batch and continuous ABE fermentations integrated with organophilic pervaporation was thoroughly tested. Poly(octyl methyl siloxane) (POMS) based pervaporation membranes were applied during fermentation and compared to the performance of polydimethylsiloxane (PDMS) based membranes. The performance of POMS based pervaporation membranes was superior both in terms of flux, separation factor and pervaporation separation index. Depending on the solvent concentration in the fermentor, total fluxes (measured during the fermentation) varied from 0.871 to 1.392 kg m−2 h−1 for the POMS (obtained at 20 mbar) and 0.564-0.719 kg m−2 h−1 for the PDMS based membrane (obtained at 9-14 mbar). Initially, simulated lignocellulosic hydrolyzates were used as a feedstock followed by the use of wheat straw hydrolyzate. Close to complete xylose conversion could only be obtained at relatively low solvent productivities. The effect of vacuum pressure (20-50 mbar) on flux and separation factor was investigated during fermentations using wheat straw hydrolyzates as feedstocks.