Impacts of main factors on bioethanol fermentation from stalk juice of sweet sorghum by immobilized Saccharomyces cerevisiae (CICC 1308)

In order to attain a higher ethanol yield and faster ethanol fermentation rate, orthogonal experiments of ethanol fermentation with immobilized yeast from stalk juice of sweet sorghum were carried out in the shaking flasks to investigate the effect of main factors, namely, fermentation temperature, agitation rate, particles stuffing rate and pH on ethanol yield and CO2 weight loss rate. The range analysis and analysis of variance (ANOVA) were applied for the results of orthogonal experiments. Results showed that the optimal condition for bioethanol fermentation should be A4B3C3D4, namely, fermentation temperature, agitation rate, particles stuffing rate and pH were 37 °C, 200 rpm, 25% and 5.0, respectively. The verification experiments were carried out in shaking flasks and 5 L bioreactor at the corresponding parameters. The results of verification experiments in the shaking flasks showed that ethanol yield and CO2 weight loss rate were 98.07% and 1.020 g h−1, respectively. The results of ethanol fermentation in the 5 L bioreactor showed that ethanol yield and fermentation time were 93.24% and 11 h, respectively. As a result, it could be concluded that the determined optimal condition A4B3C3D4 was suitable and reasonable for the ethanol fermentation by immobilized Saccharomyces cerevisiae. The conclusion in the research would be beneficial for application of ethanol fermentation by immobilized S. cerevisiae from stalk juice of sweet sorghum.