MANGANESE AND MALONATE ARE INDIVIDUAL REGULATORS FOR THE PRODUCTION OF LIGNIN AND MANGANESE PEROXIDASE ISOZYMES AND IN THE DEGRADATION OF LIGNIN BY PHLEBIA-RADIATA

The effects of high manganese [180 mu M Mn(II)] concentration and addi tion of malonate (10 mM) were studied in nitrogen-limited cultures of the white-rot fungus, Phlebia radiata. High levels of manganese alone showed no systematic influence on the production of lignin peroxidase (LiP), manganese peroxidase (MnP) or laccase. In contrast, high-mangan ese containing cultures of P. radiata showed lower efficiency in the m ineralization of C-14-ring-labelled synthetic lignin ([C-14]DHP). The highest rates of mineralization, up to 30% in 18 days, were reached in low-maganese(2 mu M)-containing cultures when malonate was omitted, D egradation of [C-14]DHP was substantially restricted by the addition o f malonate. The combination of high manganese and malonate resulted in increased levels of MnP and laccase production, whereas LiP productio n was repressed. Also, the profiles of expression of tile MnP and LiP isozymes were affected. A new P. radiata MnP isozyme of pI 3.6 (MnP3) was found in the high-manganese cultures. Addition of malonate alone c aused some repression but also stimulating effects on distinctive MnP and LiP isozymes. The results indicate that manganese and malonate are individual regulators of MnP and LiP expression and have different ro les in the degradation of lignin by P. radiata.