Chiang Mai Journal of Science

One-pot catalysis combining laccase with Co(salen) (laccase/Co(salen)) was used to improve pulp delignification focusing on LCC degradation. This one-pot catalysis achieved remarkable pulp delignification, in which the delignification rate increased from 47.6% of control, to 50.4% of laccase, to 54.7% of Co(salen), and to 59.8% of laccase/Co(salen). The carbohydrate content in LCC samples decreased from 26.8% of control, to 24.1% of laccase, to 22.7% of Co(salen), and to 20.8% of laccase/Co(salen), indicating the one-pot catalysis with laccase/Co(salen) promoted the removal of carbohydrate from LCC. GPC analysis of LCC indicated that laccase/Co(salen) significantly improved LCC degradation. Furthermore, FTIR analysis confirmed that laccase/Co(salen) increased carbonyl groups and phenolic hydroxyl groups of LCC, and decreased aromatic rings of LCC and hemicellulose groups. Structural characterization by HSQC showed that this one-pot catalysis promoted the cleavage of LCC linkages and β-O-4 bonds in LCC. The benzyl ether content in LCC samples decreased from 2.1 per 100 Ar of control, to 1.6 per 100 Ar of laccase, to 1.3 per 100 Ar of Co(salen), and to 0.8 per 100 Ar of laccase/Co(salen); the phenyl glycoside content in LCC samples decreased from 4.2 per 100 Ar of control, to 3.6 per 100 Ar of laccase, to 3.2 per 100 Ar of Co(salen), and to 1.8 per 100 Ar of laccase/Co(salen); the α-ester content in LCC samples decreased from 1.7 per 100 Ar of control, to 1.3 per 100 Ar of laccase, to 1.0 per 100 Ar of Co(salen), and to 0.4 per 100 Ar of laccase/ Co(salen); the β-O-4 content in LCC samples decreased from 21.5 per 100 Ar of control, to 17.8 per 100 Ar of laccase, to 15.5 per 100 Ar of Co(salen), and to 12.6 per 100 Ar of laccase/Co(salen). Catalytic oxidation of LCC model compound also confirmed this promotion effect.