Pretreatment of corn stover with diluted acetic acid for enhancement of acidogenic fermentation

• Diluted acetic acid pretreatment of corn stover was optimized by RSM.
• 2.712 g/L furfural cannot inhibit acidogenic fermentation.
• pH 5 can improve butyric acid fermentation and avoid propionic acid fermentation.

A Box-Behnken design of response surface method was used to optimize acetic acid-catalyzed hydrothermal pretreatment of corn stover, in respect to acid concentration (0.05–0.25%), treatment time (5–15 min) and reaction temperature (180–210 °C). Acidogenic fermentations with different initial pH and hydrolyzates were also measured to evaluate the optimal pretreatment conditions for maximizing acid production. The results showed that pretreatment with 0.25% acetic acid at 191 °C for 7.74 min was found to be the most optimal condition for pretreatment of corn stover under which the production of acids can reach the highest level. Acidogenic fermentation with the hydrolyzate of pretreatment at the optimal condition at the initial pH = 5 was shown to be butyric acid type fermentation, producing 21.84 g acetic acid, 7.246 g propionic acid, 9.170 butyric acid and 1.035 g isovaleric acid from 100 g of corn stover in 900 g of water containing 2.25 g acetic acid.