Enhanced ethanol production from carob extract by Saccharomyces cerevisiae

Carob pod has been widely used in food industry as a feed for livestock and human consumption, including sweets, biscuits and processed pekmez; a Turkish traditional carob concentrate and thus attracted the attention of producers with increasing market value. With their suitable content, carob extract are known to be utilized by using fermentation methods. The effect of various fermentation parameters such as pH, media content and inoculum size were evaluated for ethanol fermentation in carob extract. Also, in order to determine economically appropriate nitrogen sources, four different nitrogen sources were evaluated. The optimum extraction condition for carob extract was determined to be 80°C, 2h in 1:4 dilution rate (fruit: water ratio) according to the result of response surface analysis (115.3 g/L). When the fermentation with pH at 5.5 was applied, the final ethanol concentration and production rates were 42.6 g/L and 3.37 g/L/h, respectively, which were higher than using an uncontrolled pH. Among inocula sizes of 1-5%, 3% was determined as the best inoculum size. The maximum production rate and final ethanol concentration were 3.48 g/L/h and 44.51%, respectively, with an alternative nitrogen source of Meat-Bone Meal. Overall, this study suggested that carob extract can be utilized for production of ethanol in order to meet the demands of renewable energy.