Batch fermentation was performed at
30°C with 100 ml of fermentation medium in a 250-ml Erleumeyer
flask inoculated with 20% (v/v) co-immobilized gel beads. In
repeated-batch fermentation, the co-immobilized gel beads were
used for seven successive batches. At the end of each batch, the
spent medium was drained, washed with the same fermentation
medium and then replaced with fresh medium to start the next
batch. At 6-h intervals, samples were withdrawn and the concentrations
of ethanol, residual sugar and biomass (free cell and immobilized
cells) were analyzed.