Production of Bioethanol by Simultaneous Saccharification and Fermentation of Corn Meal by Immobilized Yeast

Abstract

The production of bioethanol by simultaneous saccharification and fermentation (SSF) of corn meal using immobilized cells of Saccharomyces cerevisiae var. ellipsoideus yeast in a batch system was studied in this work. The yeast cells were immobilized in Ca-alginate by electrostatic droplet generation method. The kinetics of the SSF process with immobilized yeast was assessed with various initial glucose concentrations. In addition, the effect of media supplementation with the yeast activators such as mineral salts, ZnSO4. 7H(2)O and MgSO4. 7H(2)O and vitamins, Ca-pantothenate, biotin and myoinositol was investigated. The system was compared with the SSF system with free yeast. The immobilized system was found superior to the free system since higher ethanol concentration and process productivity were obtained. The maximum increase in ethanol concentration was achieved in immobilized system when mineral salts were added. In this case, the ethanol concentration of 9.70% (w/w) was achieved after 38 hours of fermentation. Addition of the magnesium and zinc contributed to the achievement of a high productivity of the batch SSF of corn meal with immobilized S. cerevisiae var. ellipsoideus yeast, while still preserving a physical and chemical stability of Ca-alginate gel beads. High productivity of the system was attributed to the cell protection from inhibition by ethanol that was achieved by immobilization, and the activation of the yeast metabolism that was accomplished by the minerals.