Technological characterization of Geotrichum candidum strains isolated from a traditional Spanish goats' milk cheese

摘要

Forty-one strains of Geotrichum candidum isolated from Armada cheese, Sobado variety, were screened for their enzymatic activities, including proteolytic and lipolytic activities and aminopeptidase activity. The highest extracellular proteolytic activity was detected for 8 strains with values ranging between 2.086 and 4.685 mM Gly L~(-1) of milk. Extracellular lipolytic activity was high for all but one of the C. candidum strains, with values ranging between 67 and 131 nmol oleic mL~(-1). Cell-bound lipase activity showed values which were considerably lower than those for extracellular activity, ranging between 32.50 and 42.50 nmol oleic mL~(-1) and falling below 20 μmol oleic mL~(-1) in 28 strains. Aminopeptidase activity was not very high in the cell-free extract (CFE) of any of the strains, showing the highest values toward the substrate Lys-p-nitroanilide, with levels of activity ranging between 6.12 and 10.05 UE mg~(-1) protein in 8 strains. In accordance with the results obtained, four G. candidum strains were selected as co-cultures in order to study their role in the ripening of a semi-hard goat's milk cheese.