Ethanol production from high dry matter corncob using fed-batch simultaneous saccharification and fermentation after combined pretreatment.

To obtain high concentration of ethanol from cellulose, corncob was pretreated with acid and alkali to remove non-cellulose components, and then subjected to simultaneous saccharification and fermentation (SSF). An ethanol concentration as high as 69.2 g/L was achieved with 19% dry matter (DM) using batch SSF, resulting in an 81.2% overall ethanol yield. A fed-batch process using a high solid concentration was also investigated. Fresh substrate was pretreated with dilute sulfuric acid-sodium hydroxide, and then added at different amounts during the first 24 h, to yield a final dry matter content of 25% (w/v). SSF conditions with cellulose loading of 22.8 FPU/g glucan, dry yeast (Saccharomyces cerevisiae) loading of 5 g/L and substrate supplementation every 4h yielded the highest ethanol concentration of 84.7 g/L after 96 h. This corresponded to a 79% overall ethanol yield.