Efficient ethanol production from inulin by two-stage aerate strategy

A major concern for ethanol production from inulin-containing materials, is the higher unconverted sugar, which increases the cost of ethanol production and wastewater treatment. Some key factors, such as inulinase, biomass or aeration rates, were studied to solve the problems in the process of ethanol fermentation from inulin. It was showed that more inulinase and increasing inoculum size can shorten the fermentation time, but could not reduce residual sugars. Two-stage aerate strategy was developed to utilize the remained sugars: keep the aeration at 5 h−1 at the first 12 h, and drop it to 1.2 h−1. Under this condition, contradiction between fermentation time and high ethanol yield was solved (60 h and 0.43 g g−1), and the final residual sugar concentration decreased to about 10 g L−1 with 98 g L−1 ethanol. The ethanol productivity was up to 1.63 g L−1 h−1, which is the highest productivity of ethanol fermentations from inulin-containing materials.