Role of organic acid chelators in manganese regulation of lignin degradation by Phanerochaete chrysosporium.

Nitrogen, carbon, and manganese are potent regulators of lignin degradation, but although nitrogen and carbon elicit a generalizated response when cells are starved, manganese is a relatively specific regulator of lignin and manganese peroxidase (LiP and MnP, respectively). At high manganese levels, MnP is induced, and LiP is repressed. At low Mn levels, MnP is repressed, and LiP is induced. Organic acid chelators are very important in attaining LiP repression with high Mn. Both mineralization and lignin depolymerization are regulated by manganese in the presence of organic acid chelators. As long as the chelators keep Mn(II) and Mn(III) in solution, repression is observed, but eventually, dismutation reactions cause the formation and precipitation of Mn (IV) as MnO2. Repression is immediately relieved, and depolymerization and mineralization proceed at a high rate.