TREATMENT OF SWEET GUM LIGNIN BY LACCASE AND LMS

Cellulolytic enzyme lignin (CEL) from sweet gum is treated by laccase and laccase/mediator system(LMS). Phenolic hydroxyl content of lignin is measured, and IR, GPC, 13C-NMR spectrograms are analyzed. Compared with control sample, phenolic hydroxyl content of lignin is a little higher after laccase treatment, whereas they are lower after LMS treatment. In LMS, lignin modification by laccase/ABTS is greater than by laccase/VA. It is found from IR that in lignin treated by laccase and LMS, relative content of siringyl hydroxyl group is higher, and α- conjugated carbonyl group content is a little higher. From GPC analysis, compared with control sample, molecular weight decrease after the treatment by laccase and LMS. And the decrement is greater by laccase alone than by LMS. According to 13C-NMR, relative content of carbonyl group and methoxyl group increase during the treatment by laccase alone, but the amount of them are lower after LMS treatment. And the amount of Cαand Cβ in β-O-4 has a little decrement after LMS treatment. It indicates that the oxidation of lignin by laccase and LMS proceed through different reaction pathways.