PRODUCTION OF ETHANOL BY IMMOBILIZED WHOLE CELLS OF ZYMOMONAS-MOBILISIN AN EXPANDED BED BIOREACTOR

Whole cells of Zymomonas mobilis, immobilised on pectin beads, were st ablised by curing in a mixture of 0.2 M CaCl2 .2H2O and Na2B4O7 . 10H( 2)O for 24 h at 4 degrees C. Ethanol fermentation was studied using di fferent glucose concentrations (50-200 g/litre) by these immobilised b eads. The kinetics of this process was studied in a glucose step-feedi ng system with different total glucose concentrations (150 and 200 g/l itre) in a specially designed shake flask. Immobilised whole cells wer e also used for ethanol fermentation in an expanded bed bioreactor and its performance characteristics were compared with those of a regular batch mechanically stirred tank bioreactor Fermentation rates and eth anol yields were higher in the expanded bed bioreactor system than in the batch mechanically agitated stirred tank bioreactor The stabilised pectin beads were damaged less in the expanded bioreactor than in the regular batch stirred tank reactor.