Development of immobilized cell systems for biotechnological processes

Cell immobilization permits controlled and repeated use of enzymes in biotechnological processes. The purpose of this thesis is to develop a new cell entrapment method and new applications of cell adsorption.;Various types of cloths were examined for adsorption of microbial cells: epichlorohydrin-triethanolamine (ECTEOLA)-, polyethylenimine (PEI)-, naphthyl- and unmodified cotton cloth, cellulose acetate, and polyester. To develop immobilized cell population on cloth (cell cloth), the cloths were wetted with microbial cultures, incubated and periodically rinsed with growth media for few days. Cotton cloth was found to be a superior adsorbent.;Yeast cloths parallely fixed in a fermentor were examined for ethanol batch fermentation from the Jerusalem artichoke tuber hydrolysate. Circulation of media significantly increased ethanol productivity. The thickness of yeast layer and ethanol productivity increased with time until maximum productivity of 20 g of ethanol per liter fermentor per hour was obtained. The productivity remained constant for 60 days.;Six industrial bacteria formed immobilized populations on cotton cloth. The bacterial films generated free cells at significant and stable rates for at least 60 days. By retaining these films in a fermentor, the films were used as resident inocula in repeated batch fermentations. An equation for the rate of cell mass generation from the resident inocula was developed.;Microbial cells were entrapped in porous cellulose acetate aggregates. Cotton cloth segments were dipped in a cell suspension in cellulose acetate in aqueous acetone and air dried. The cell cloth was stabilized by treatment with polyethyleneimine followed by alkaline glutaraldehyde containing dithionite. L-Aspartase containing Escherichia coli cell cloth exhibited higher and stable aspartate productivity than gel-entrapped systems.;Contamination did not decrease the capacity of bacterial films as resident inocula for repeated batch fermentation. Since the contaminants are removed along the culture, the resident inoculum batch fermentation is resistant to contamination problems.;Using the resident inoculum method, Streptomyces secondary metabolites, thienamycin and cephalosporin C were produced at maximal levels during 20 cycles of three day batch fermentations.;A cloning vector, pBR322 was more stably maintained in E.coli immobilized on cotton cloth than in free cells. Therefore, the resident inoculum method would be useful in batch production of recombinant DNA products.