LIGNINOLYTIC SYSTEM FORMATION BY PHANEROCHAETE-CHRYSOSPORIUM IN AIR

This study characterizes the effect of oxygen concentration on the syn thesis of ligninolytic enzymes by Phanerochaete chrysosporium immobili zed on polyurethane foam cubes in a nonimmersed liquid culture system and maintained under different carbon-to-nitrogen (C/N) ratios and lev els. Lignin peroxidase (LIP) activity was obtained in cultures exposed to air when the C/N ratio was low (7.47), i.e., when nitrogen levels were high (C/N = 56/45 mM) or carbon levels were low (C/N = 5.6/4.5 mM ). At the low C/N ratio, the fungus was carbon starved and did not pro duce extracellular polysaccharides. At a high C/N ratio (153), i.e., u nder conditions of excess carbon (nitrogen limitation) (C/N = 56/2.2 m M), cultures exposed to air produced large amounts of polysaccharide, and LIP activity was detected only in cultures exposed to pure oxygen. Under high-nitrogen conditions, LTP production was 1,800 U/liter in c ultures exposed to pure oxygen and 1,300 U/liter in cultures exposed t o air, with H1 and H2 being the main isoenzymes. The oxygen level did not significantly alter the isoenzyme profile, nor did low-carbon cond itions. The formation of manganese peroxidase was generally less affec ted by the oxygen level than that of LIP but tvas considerably reduced by a low C/N ratio. The effects of oxygen level and C/N ratio on the synthesis of glyoxal oxidase paralleled their effects on LIP synthesis except in the case of high nitrogen, which totally suppressed glyoxal oxidase activity.