(398am) Intensification of the Enzymatic Hydrolysis of Recycled Paper Fiber Fragments Using Membrane Separations

Papermaking fibers, particularly waste fibers from recycling operations can be a valuable resource for biofuels (ethanol), and sustainable products such as bioplastics or biochemicals. The amount of lignin in such fibers is much lower than native wood or other plant based lignocellulosic resources eliminating the need for complex and expensive pretreatment processes. Moreover, the removal of hornified cellulosic fines from recycled pulps can accelerate water removal from the pulps on the papermachines and in the dryer sections, leading to significant productivity increases. Inter-fiber bonding in the paper sheet is improved due to a lower ‘waste fines’ content, reducing the use of strength agents like starch and improving sheet quality.

The present work develops a physico-chemical model for the kinetics of enzymatic hydrolysis of cellulosic pulp fines from recycled linerboard mills. Batch kinetics representing hydrolysis in a fixed agitated volume of the fines suspension is considered. Cellulosic fines are assumed to be spherical and porous, with the cellulase enzymes diffusing and adsorbing onto the interior pore surfaces. Enzymatic reactions result in the production of glucose which diffuses outward. The mechanistic role of inhibitory mineral (ash) fillers and the application of suitable surfactants to cover their surfaces and improve cellulose hydrolysis is considered.

Optimal usage of the enzyme catalyst is a critical part of this process. In this paper, microfiltration membranes are used to separate the enzymes and recycled so that the effective catalyst concentration is higher and overall enzyme usage is minimized. Experimental results showing the impact of flow rates, concentrations of substrate and concentrations as well as other variables such as pH and temperature are shown. Mathematical models for determining the optimal designs of both external and internal membrane bioreactors were set up for analysis.