HEMICELLULOLYTIC ENZYMES IN P-STRAINS AND S-STRAINS OF HETEROBASIDION-ANNOSUM

The secretion of several hemicellulolytic enzymes and endoglucanase wa s studied in S- and P-group strains of a wood-rotting pathogen, Hetero basidion annosum, using enzyme activity assays and isoelectric focusin g. In liquid cultures supplemented with birch sawdust or pure xylan, b oth strains of the fungus produced xylanases, mannanases, endoglucanas es and alpha-galactosidases. Low activities were detected in cultures containing only glucose as a carbon source. When S-strain cultures wer e provided with a carrier matrix, protein secretion to the culture med ium started earlier and was significantly increased compared to free c ell cultures. This was not the case with the P-strain. In both strains of H. annosum the pH of the birch sawdust culture medium fell within 12 d to below 3.5, and then started to increase towards the end of the cultivation period. The increase in ph appeared to correlate with the formation of hemicellulolytic and endoglucanase activities. The isoen zyme patterns of xylanase, mannanase and endoglucanase were typical fo r P- and S-strains. In P-strain cultures containing xylan, a xylanase with an alkaline pi value was induced which, however, was absent when the P-strain was grown with the birch sawdust substrate. In the P-stra in the mannanase pattern at the early stage of growth was comparable t o that of the S-strain at the later stages of growth on birch sawdust medium. Later in the growth of the P-strain, this pattern was replaced by mannanases with more acid pI values. The relative intensities of t he individual endoglucanases varied between the P- and S-strains.