CARBON SOURCE CONTROL ON BETA-GLUCANASES, CHITOBIASE AND CHITINASE FROM TRICHODERMA-HARZIANUM

The cell-wall degrading enzymes beta-glucanase and chitinase have been suggested to be essential for the mycoparasitic action of Trichoderma species against plant fungal pathogens. For this reason, the production in different carbon sources of extracellular beta-1,3-glucanase, beta-1,6-glucanase, chitobiase and chitinase was studied in a mycoparasitic strain of Trichoderma harzianum. Maximal beta-glucanase specific activities were detected in media supplemented with either pustulan (beta-1,6-glucan), nigeran (alpha-1,3-glucan alternating with alpha-1,4-glucan), chitin or Saccharomyces cerevisiae or Botrytis cinerea purified cell walls, whereas the highest chitinase specific activity was obtained in medium supplemented with chitin. Furthermore, beta-glucanase, chitobiase and chitinase activities showed an increase parallel to increasing concentrations of either pustulan or chitin added to the cultures, although the extent of this increase varied with the different enzymes. The culture filtrates of T. harzianum grown in these carbon sources also showed lytic activity on purified cell walls of S. cerevisiae and B. cinerea. The enzyme synthesis seemed to be repressed by glucose, 8-hydroxyquinoline, which inhibits transcription, or cycloheximide, an inhibitor of protein synthesis.