COPPER-DEPENDENT DEPOLYMERIZATION OF LIGNIN IN THE PRESENCE OF FUNGALMETABOLITE, PYRIDINE

Thus far, it has not been recognized that copper complexes are able to depolymerize lignin under physiological conditions of white rot decay . However, we have found that both phenolic and non-phenolic synthetic lignins were intensively depolymerized by Cu(II) and lipid hydroperox ide model compounds in the presence of a metabolite of ligninolytic fu ngi, pyridine at room temperature in aqueous media. Treatment of C-14- labeled oxygen-prebleached kraft pulp (OKP) by the copper-dependent re action evidenced effectiveness of this reaction for the delignificatio n of kraft pulps. In contrast to the organic peroxide system, Cu(II)/p yr/H2O2 system was much less effective for the lignin depolymerization . However, treatment of unbleached kraft pulp (UKP) by Cu(II)/H2O2 and Cu(II)/pyr/H2O2 systems demonstrated that the damage of cellulose was suppressed by the coordination of pyridine although high brightness g ain was obtained independently of the presence of the coordinator. Spi n trapping experiments demonstrated that not hydroxyl radical but supe roxide anion is involved in the Cu(II)/pyr/H2O2 system. This finding n ot only introduces a new concept of non-enzymatic lignin biodegradatio n by wood-degrading fungi but also presents a new strategy for decompo sing lignin and lignin-related compounds by copper complexes and perox ide-producing system. (C) 1998 Elsevier Science B.V. All rights reserv ed.