Inhibition of lignin-derived phenolic compounds to cellulase

Lignin-derived phenolic compounds are universal in the hydrolysate of pretreated lignocellulosic biomass. These phenolics reduce the efficiency of enzymatic hydrolysis and increase the cost of ethanol production. Tianjin University researchers led by Lei Qin investigated inhibition of phenolics on cellulase during enzymatic hydrolysis. The team used vanillin as the typical lignin-derived phenolics and Avicel as cellulose substrate.

As vanillin concentration increased, cellulose conversion after 72-h enzymatic hydrolysis decreased from 53 to 26%. Enzyme deactivation and precipitation were detected with the vanillin addition. The enzyme concentration and activity consecutively decreased during hydrolysis. Inhibition was also found to be mitigated by increasing cellulose loading or cellulase concentration.

The degree of inhibition showed linear relationship with vanillin concentration and exponential relationship with the cellulose loading and cellulase concentration. Temperature and pH also showed no significant impact on inhibition degree. The presence of hydroxyl group, carbonyl group, and methoxy group in phenolics also affected the inhibition degree.