Microreactor-based mixing strategy suppresses product inhibition to enhance sugar yields in enzymatic hydrolysis for cellulosic biofuel production

Abstract

A novel microreactor-based energy-efficient process of using complete convective mixing in a macroreactor till an optimal mixing time followed by no mixing in 200–400μl microreactors enhances glucose and reducing sugar yields by upto 35% and 29%, respectively, while saving 72–90% of the energy incurred on reactor mixing in the enzymatic hydrolysis of cellulose. Empirical exponential relations are provided for determining the optimal mixing time, during which convective mixing in the macroreactor promotes mass transport of the cellulase enzyme to the solid Avicel substrate, while the latter phase of no mixing in the microreactor suppresses product inhibition by preventing the inhibitors (glucose and cellobiose) from homogenizing across the reactor. Sugar yield increases linearly with liquid to solid height ratio (rh), irrespective of substrate loading and microreactor size, since large rh allows the inhibitors to diffuse in the liquid away from the solids, thus reducing product inhibition.