Effect of osmotic potential on synthesis and secretion of polygalacturonase and cellulase by Geotrichum candidum

Abstract

In liquid cultures of Geotrichum candidum, amended with KCl, mannitol, or polyethylene glycol 400 to control osmotic potential, levels of both intracellular and extracellular endopolygalacturonase fell off rapidly with decreasing osmotic potential in the range of −0.5 to −2.5 MPa. Concentrations (units per millilitre) of intracellular endopolygalacturonase were higher than those of extracellular endopolygalacturonase at all osmotic potentials tested. The ratio of intracellular to extracellular endopolygalacturonase concentration increased with decreasing osmotic potential; this became most pronounced below −1.5 MPa. It appeared that the major effect of osmotic potential was on endopolygalacturonase synthesis with a minor effect on endopolygalacturonase secretion from the cell. Levels of intracellular and extracellular cellulase also decreased with decreasing osmotic potential, although the effect was much smaller than with endopolygalacturonase. However, the ratio of intracellular to extracellular cellulase concentration did not change significantly with changes in osmotic potential. This indicated that only the synthesis of cellulase was affected.