Bioethanol production from sweet sorghum stalk juice with immobilized yeast

The experiments of ethanol fermentation from sweet sorghum stalk juice with immobilized yeast at different conditions, including temperature, pH, particles stuffing rate and initial substrate concentration, were carried out in 250 ml shaking flasks to obtain suitable parameters by analyzing the values of ethanol formation rate (rp/s) and ethanol-sugar conversion ratio (Yp/s), respectively. The results indicated that fermentation temperature of 33 °C, pH of 4.5, particles stuffing rate of 25% and the initial sugar concentrationof 218.1 mg·ml-1 could be selected. The results of verification experiments in 250 ml shaking flasks with the corresponding conditions showed that the value of rp/s and Yp/s were 0.0486g·g-1·h-1 and 0.4005 g·g-1, respectively. In addition, the results of rp/s and Yp/s in the further verification experiments of 1L shaking flasks were 0.0465g·g-1·h-1 and 0.4248 g·g-1, respectively, which could be deduced that the selected conditions were suitable and reliable for ethanol production from sweet sorghum using immobilized yeast.