Hollow-fiber membrane-based extractive bioreactors a whole cell immobilization technique

A new whole cell immobilization support of chopped microporous hollow fibers has been investigated. Chopped microporous hydrophobic or hydrophilic hollow fibers were used to grow cells in the fiber lumen as well as on the fiber outside surface. Such chopped fibers with immobilized cells were later utilized in a tubular fermentor to carry on ethanol fermentation by Saccharomyces cerevisiae for an extended period. Detailed experimental evidences of the dependency of immobilized cell density in shaker culture studies on the chopped hollow fiber diameter, length and type have been obtained. A model developed to predict the density of immobilized S. cerevisiae cells in chopped hollow fibers correctly suggests that fibers with smaller diameters and lengths have much higher cell density. Two different models were formulated to describe the fermentation performance in a tubular fermentor with very high immobilized cell density.; A novel bioreactor incorporating hydrophobic microporous hollow fiber (HMHF) membranes has been used. Detailed characterization of the O{dollar}sb2{dollar} transport rate into the broth from the HMHF-s in a tubular fermentor has been made. A study of the CO{dollar}sb2{dollar} stripping rates has also been undertaken. These measurements provide a base condition for studies on nutrient supply and product removal in the hollow fiber bioreactor. In the second set of studies, how to effectively supply O{dollar}sb2{dollar} to and remove CO{dollar}sb2{dollar} from a continuous ethanol fermentation system using a hollow fiber-based bioreactor has been illustrated. Pure O{dollar}sb2{dollar} at 11 psig was found to increase ethanol productivity by 80% at 125 cc/hr of substrate flow rate.; A toxicity study carried out to screen the biocompatible solvent to be used in a hollow fiber membrane-based fermentor - extractor suggested oleyl alcohol and dibutyl phthalate to be the best solvents. In the second part, using such solvents the beneficial effects on in situ dispersion-free solvent extraction of ethanol for a 300g/l glucose substrate feed are demonstrated in a bioreactor with chopped hollow fiber immobilization of yeast. The fermentor - extractor model predictions are in good agreement with the experimental data. (Abstract shortened with permission of author.)...