Enhanced production of cellobiose dehydrogenase in cultures of Phanerochaete chrysosporium supplemented with bovine calf serum.

Abstract

The enzyme cellobiose dehydrogenase (CDH), produced by many wood-degrading fungi has, in recent years, attracted considerable interest for its possible role in both cellulose and lignin degradation. To characterize the enzyme better and to identify its role in the degradation of wood and wood components, it is desirable to produce it in higher amounts. We report here that the addition of bovine calf serum to cellulose-grown cultures of Phanerochaete chrysosporium enhances the production of certain enzymes, CDH in particular. The highest CDH production was obtained with 45 ml of serum/litre of medium added on day 3 or 4. The resultant CDH yield was approx. 700-800 units/litre, which was 3.5-4 times higher than that in cultures without serum. Serum addition also enhanced the production of beta-glucosidase. However, the impact on CDH production was the most dramatic. The enhanced enzyme production cannot be explained by increased rates of spore germination, simple nutrient effects or cofactor effects. Fractionation of serum by Cohn's fractionation technique showed that the albumin (BSA) fraction had almost the same effect as whole serum. However, purified BSA had less effect than crude BSA (fraction V of Cohn's fractions), suggesting that an additional factor, probably a protease inhibitor in serum, also contributed to the effect of serum.