High ethanol productivities using small Ca-alginate beads of immobilized cells of Zymomonas mobilis

• DOI: 10.1007/bf00158688
• Publication Date: 2004-11-02T14:51:42Z
• Authors: Argyrios Margaritis; Pramod K. Bajpai; J. Blair Wallace
• Keywords: Zymomonas mobilis; Dilution; Calcium alginate; Bead

Zymomonas mobilis cells were immobilized into small 1 mm diameter beads of Ca-alginate in order to minimize mass transfer limitations and maximize immobilized cell activity. A combination of small bead size with a high cell concentration of 58 g dry wt. cell per lit. bead volume resulted in high ethanol productivities using a newly designed packed bed bioreactor system. Steady-state dilution rates ranging from 0.4 h-1 to 3.9 h-1 were run resulting in a maximum productivity of 102 g ethanol/l/h for an inlet substrate concentration of 100 g glu/l and 87% conversion. The bioreactor was run continuously at a fixed dilution rate for 384 h and short intermittent treatment of the beads with CaCl2 temporarily increased ethanol productivity to a maximum of 116 g ethanol/l/h.