Stimulation of hydrogen peroxide production in the white rot fungus Bjerkandera sp strain BOS55 by antagonism with bacteria

White rot fungi produce hydrogen peroxide (H2O2) by different extracellular oxidases as part of their ligninolytic system. A previous study showed that H2O2 production was the limiting factor in the degradation of polyaromatic xenobiotics such as anthracene and Poly R-478. In this study we were able to stimulate the production of H2O2-generating aryl alcohol oxidase (AAO) and concomitantly increase the H2O2 concentration in cultures of Bjerkandera sp. strain BOS55 by introducing the bacterial strain RH-94 to the fungal culture. In the presence of bacterium, the AAO activity and H2O2 concentration were enhanced up to ten-fold reaching peak values of 39 nmol ml(-1) min.(-1) and 32 mu M, respectively. The addition of filter sterilized bacterial broth gave a similar response indicating that extracellular components of bacterial cultures are responsible for the stimulation. Moreover, the fungus with bacteria added was able to decolorize the dye Poly R-478 twice as fast as the fungus alone. These results suggest that the ligninolytic system can play a role in the defense system of white rot fungi against antagonistic microorganism. Secondly, the increased H2O2 concentration may also be beneficial for lignin degradation.