Study on The Process of Fed-Batch Very High Gravity Ethanol

Abstract:

Very high gravity（VHG） batch ethanol fermentation has the problems of high residual sugar concentration and low sugar-ethanol conversion rate. It was found that the concentrations of dextrin and reducing sugar increased gradually with the increase of the concentration of the mixture. The reasons for the high concentration of dextrin and reducing sugar were mainly related to the activity of saccharification enzyme and the sugar utilization ability of yeast. To resolve these problems，process of fed-batch very high gravity ethanol fermentation with massive inocula was proposed in the study，and the inoculum concentration，initial feeding time，feeding duration and feeding mode were optimized. Results showed that the optimum process is 30% inoculation concentration，the initial feeding time after inoculation 8 h，the feeding duration 20 h and constant feeding speed. Compared with the batch fermentation，the residual sugar decreased by 6.5 g/L，meanwhile，the sugar-ethanol conversion rate of increased by 3.2%.