Hydroxycinnamic acids release during bioconversion of corn stover and their effects on lignocellulolytic enzymes

Hydroxycinnamic acids released during alkaline pretreatment of lignocellulose, especially p-coumaric acid (p-CA) and ferulic acid (FA), negatively affect the enzymatic hydrolysis and fermentation. However, the mechanism of this effect is not well understood. In this study, we investigated the releasing behavior and negative effect and examined the underlying mechanisms. The results demonstrated that the hydrogen peroxide concentration and biomass loading affected the release of p-CA and FA significantly during alkaline hydrogen peroxide (AHP) pretreatment of corn stover. p-CA and FA mainly inhibited the activity of endoglucanase, xylanase, and filter paper activity (FPA), while the amount of lignocellulolytic enzyme protein was not affected. Thus, they acted as inhibitors of enzyme activities. Molecular docking study indicated that p-CA and FA inhibited the lignocellulolytic enzyme activity and enzymatic hydrolysis efficiency mainly by forming non-covalent bonds to specific amino acids in the active sites of the lignocellulolytic enzymes.