Alcoholic Fermentation Using Immobilized Cells in Calcium Alginate

This work refers to alcoholic fermentation carried out using immobilized cells. The Saccharomyces cerevisiae cells were immobilized in calcium alginate and in chitosan-covered calcium alginate beads. Ethanol was obtained for the fermentation of both glucose or sucrose. The batch fermentations were carried out in an orbital shaker. The reaction was monitored with the use of an HPLC that assessed the concentration of products and substrate. Results show that both calcium alginate immobilized beads and chitosan-covered calcium alginate immobilized beads could be used in eight sequential fermentation cycles of 10 h each. The final concentration of ethanol using free cells was 40 g L-1 and the yields using glucose and sucrose as carbon sources were 78% and 74.3%, respectively. For immobilized cells in calcium alginate beads, the final ethanol concentration in the glucose fermentation was 32.9 ± 1.7 g L-1 with a 64.5 ± 3.4% yield. The final ethanol concentration for the sucrose fermentation was 33.5 ± 4.6 g L-1 with a 64.5 ± 8.6% yield. For immobilized cells in chitosan-covered calcium alginate beads, the ethanol concentration from glucose was 30.7 ± 1.4 g L-1 with a 61.1 ± 2.8% yield. The final ethanol concentration from sucrose was 31.8 ± 6.9 g L-1 with a 62.1 ± 12.8% yield. There was no need to use antibiotics and no contamination was observed in the batches. After the eighth cycle, a significant rupture of the beads was observed thus making them inappropriate for use in another cycle.