Enhanced production of bioethanol and ultrastructural characteristics of reused Saccharomyces cerevisiae immobilized calcium alginate beads

► We examine optimal batch fermentation condition of immobilized yeast with Ca-alginate beads. ► Reused yeast immobilized beads give excellent results in converting glucose to ethanol. ► Short fermentation time and the high ethanol yield with the reused beads are due to a higher yeast population and porosity. ► We explain and confirm “egg-box” model of alginate matrix structure using TEM observation.