Comparative Detoxification of Vacuum Evaporation/Steam Stripping Combined with Overliming on Corn Stover Prehydrolyzate

Two kinds of physical methods, vacuum evaporation and steam stripping, combined with overliming (calcium hydroxide) were applied to remove inhibitors which were produced simultaneously during the pretreatment of lignocellulosic biomass. Corn stover was steam exploded; the filtrate was hydrolyzed with dilute sulfuric acid. The acid hydrolyzate was then detoxified and fermented by yeast. Physical methods could remove volatile compounds from the acid hydrolyzate. When the acid hydrolyzate was condensed 11.13 times by vacuum, it could remove 59.89% formic acid and 77.72% acetic acid. At a steam stripping time of 120 min, 58.79% formic acid and 80.83% acetic acid were removed. While furfural was stripped off completely by the two methods. Overliming could reduce the contents of furans, however, sugars, especially pentoses, were also removed partially. The results of fermentation of the detoxified and undetoxified acid hydrolyzates by
Pichia stipitis
CBS 5776 showed that "steam stripping(120 min) + overliming(pH11, 60°C, 90 min)" could improve its fermentability significantly. In 24 h, the ethanol reached its peak of 15.92 g/l, 80.34% of theoretical.