beta-Glucosidase excretion by Trichoderma pseudokoningii: correlation with cell wall bound beta-1.3-glucanase...

The formation and excretion of beta-glucosidase from Trichoderma pseudokoningii was studied during growth on different carbon sources. The enzyme was present under all conditions examined, but increased activity was found during growth on carbon sources favouring slow growth. Two different patterns of beta-glucosidase excretion were observed: on carbon sources allowing fast growth a relatively high percentage of total activity was found in the culture fluid, which decreases as the culture grows older, but which increases again during the phase of cell lysis; on carbon sources favouring slow growth, excretion is initially low, but commences at later culture stages. Changes in cell wall composition and cell wall lytic enzyme activities associated with the cell walls were examined during phases of high and low ratios of extracellular to cell-wall bound beta-glucosidase activities. With no component of the cell wall (chitin, alpha-glucan, beta-glucan, galactosamine) could correlation with beta-glucosidase excretion be identified. Among a number of cell-wall lytic, cell-wall associated enzymes (alpha-glucanases, beta-glucanases, glucosaminidase, galactosaminidase), beta-1.3-glucanase activity correlated well with the excretion of beta-glucosidase. The results suggest a possible role of beta-1.3-glucanases in the mechanism of release of beta-glucosidase from cell walls of T. pseudokoningii; this is discussed.