Optimization of ethanol production from carob pod extract by using Saccharomyces cerevisiae cells immobilized in Ca-alginate

Usage of food wastes and agricultural products with their high sugar content in biotechnological processes has increased recently because the production of value added products by using these resources provide a positive contribution to the economy. In this study, optimization of ethanol production from carob pod extract was carried out by using immobilized Saccharomyces cerevisiae cells. Consequently, four-factor Box-Behnken Response Surface Method design was used for optimization. Results showed that Ca-alginate concentration and the amount of cells that entrapped in beads were significant for yield values and Ca-alginate concentration, agitation rate and the amount of cells that entrapped in beads were significant for production rates. Optimum conditions for ethanol fermentation from carob pod extract by using Saccharomyces cerevisiae cells were determined to be %2 Ca-alginate concentration, 150 rpm agitation rate, %5 amount of cells that entrapped in beads and pH 5.5. After validation experiments yield, production rate and sugar utilization rate were 46.23%, 3.19 g/L/h and 90.66% respectively as well as the fermentation time was decreased to 24 hours. And also cycle number of the immobilized cells was determined and the immobilized cells could be used for five cycles successfully although it had been a decrease to yield. Finally, carob pod extract was used for ethanol fermentation by controlled and uncontrolled pH without any enrichment and the results show that carob pod extract can be used without any enrichment.KEYWORDS: Carob pod extract, ethanol, Saccharomyces cerevisiae, immobilization, Response Surface Method