INOSITOL-MEDIATED INVERTASE SECRETION IN SACCHAROMYCES SP. W-4

In this study, the effects of inositol addition on invertase secretion in Saccharomyces sp. W4 were examined. We found that invertase secret ion in this strain was repressed when the completely synthetic medium lacking exogenous inositol contains more than 0.2% (w/v) glucose; howe ver, when the yeast cells were grown in the same medium plus inositol, repression of invertase secretion in this strain occurred only at glu cose concentrations higher than 2.0% (w/v). Furthermore, when sucrose was used as carbon source, increased invertase activity was observed i n the presence of inositol. Repression occurred only at sucrose concen trations above 4.0% (w/v). More cell growth occurred and less residual reducing sugar was left in the inositol-containing medium than in the inositol-deficient medium as glucose or sucrose concentration was inc reased. These results demonstrate that inositol supplementation could derepress invertase secretion and cell growth in this yeast strain to some extent and sucrose was more suitable for invertase production tha n glucose. When the repressed yeast cells were transferred to the synt hetic medium with low concentration glucose or sucrose, they could syn thesize more extracellular invertase in the presence of inositol than in the absence of inositol. (C) 1997 Elsevier Science Inc.