Concentrating Cellulases Using a Temperature‐Sensitive Hydrogel: Effect of Gel Particle Size and Geometry

Abstract

AbstractA temperature‐sensitive poly (N‐isopropylacrylamide) hydrogel was used to concentrate cellulases from Trichoderma reesei. The effect of gel size and geometry on separation efficiency and weight change rate was studied. Gel weight change was reproducible over six cycles of short swelling and collapsing (2 h each) experiments, but the gel weight change capacity of small and large cubes was 90% and 62% of small extruded gel, respectively. The gel weight change capacity of large extruded gel and chopped gel was comparable to that of small extruded gel. Cellulase separation efficiency increased up to 64% for large cubes, but it was lower than 80–97% for comparably sized solutes reported in the literature. Small extruded gel reached its equilibrium weight in 2–3 h, but it took more than 200 times longer for gel disks to reach equilibrium weights. Initial solution flux (surface‐specific water release/sorption rate) during swelling and collapsing was 1065–2450 g/m2·h, but flux decreased rapidly with time. Skin formation was partially responsible for the slower weight change rate of larger gels, but chopped gel also formed skin at collapse temperatures higher than 37 °C. Skin formation was not observed for small extruded gel up to 50 °C. During gel disk collapsing experiments, transparent bubbles trapping pressurized water initially were observed all over the gel surface, and some of the bubbles on the disk edge did not collapse until the gel approached an equilibrium weight.