Lowering the cationic demand caused by PGA in papermaking by solute adsorption and immobilized pectinase on chitosan beads

Pectins or polygalacturonic acids (PGA) were originated from alkaline peroxide bleaching of mechanical pulps and considered as the dominant troublesome substance, which seriously decreased the runability of the paper machine in process water closure. To find wide application of enzymes in lowering PGA concentration in papermaking industries, cross-linked chitosan beads were prepared. Results showed that the PGA-absorption capability of chitosan beads was greatly affected by its cross-linking degree. The activity of immobilized pectinase on cross-linked chitosan beads were also investigated and the highest activity of binary immobilized pectinase on cross-linked chitosan was achieved using 1.00% of activating reagent or 0.005% of glutaraldehyde. Cationic demand of PGA solutions was obviously lowered by increasing the temperature of enzymatic treatment. GPC analysis showed a sharp decrease in the molecular weight of PGA after enzymatic treatment. Besides, operational stability of the immobilize pectinase was analyzed to evaluate its application potential.