Pectinolytic activity of Saccharomyces fragilis cultured in controlled environments.

Seven of 30 yeast stock cultures, covering nine genera, and 13 of 39 yeasts isolated from grapes gave positive reactions when screened for pectinolytic activity on pectin gel plates. The seven stock cultures covered six species and four genera. Only one of the yeasts, Saccharomyces fragilis Y49, excreted discernible pectinolytic activity into the fluid of shake flask cultures; the activity was partially constitutive and was repressed by high oxygen tensions.