Production of bioethanol from corn meal hydrolyzates by free and immobilized cells of Saccharomyces cerevisiae var. ellipsoideus

The ethanol fermentation of enzymatically obtained corn meal hydrolyzates by free and immobilized Saccharomyces cerevisiae var. ellipsoideus yeast in a batch system was studied. The initial glucose and inoculum concentration and the time required for the efficient ethanol production were optimized taking into account parameters such as ethanol concentration, ethanol yield and volumetric productivity. The yeast cells were immobilized in Ca-alginate by electrostatic droplet generation method. An optimal initial inoculum concentration of 2% (v v−1) and optimal fermentation time of 38 h for both immobilized and free yeasts were determined. Optimal initial glucose concentrations of 150 and 176 g l−1 for free and immobilized system were achieved, respectively. The immobilized cell system was superior to the free cell system since higher ethanol tolerance and productivity and lower substrate inhibition were detected.