Investigation of membrane bioreactor for in situ product removal based on silicone rubber membrane module

In many biotransformation productions performed in ordinary batch or fed-batch bioreactors, product inhibition of a production strain strongly decreases the yield and effectivity of the process. A way to overcome this effect is to apply extractive biotransformation, which means to continually remove the product from the fermentation broth. Nowadays, application of a membrane bioreactor with an immersed capillary membrane module is used as a promising solution for this case. In this work, we propose the membrane bioreactor for extractive bioproduction of chemical specialties consisting of a 3 L mixed tank bioreactor with an immersed extractive tubular membrane module. As the membrane material, silicone rubber tubes were chosen as it shows many advantages compared to other materials. As the model solute for the extraction, 2-phenylethanol (rose aroma) was chosen due to its strong inhibition effect on the production strain (Saccharomyces cerevisiae). The solute partition coefficient in the extraction system containing solute, water and silicone rubber was measured as well as the solute diffusion coefficient for the silicone rubber membrane. Three different membrane modules made of silicone rubber tubes were manufactured and tested in series of extraction experiments performed in the membrane bioreactor at different operation conditions including different biomass concentration, stirring rate, and aeration rate. Experimental data were compared with the prediction of mathematical model programmed in MATLAB with good accuracy.