Technological properties of Enterococcus faecium isolated from ewe's milk and cheese with importance for flavour development

Abstract

Eight Enterococcus faecium strains isolated from ewe milk and artisanal cheese from northwest Argentina were screened for biotechnological properties relevant to flavour development. The API ZYM test showed absence of proteases, presence of high amounts of peptidases, and high esterase-lipase activities. Low extracellular proteolytic activity was observed. Most strains produced diacetyl in milk, with E. faecium OvL 214 and OvL 254 being the best producers. Biomass and growth rate increased when citrate was added to the medium, suggesting that these strains could use citrate as a main energy source. After 24 h of incubation, citrate was completely consumed in complex medium supplemented with glucose and citrate. An average of 17% residual citrate was detected in complex media supplemented with citrate. For all strains, esterase activity was detected up to alpha-naphthyl-caproate. They hydrolyzed alpha-naphthyl derivatives of fatty acids in this order: C3 > C6 > C4 > C8 > C2. Post-electrophoretic detection of esterase activities revealed the presence of multiple esterases. Hydrolysis of tributyrin, tricaprylin, and milk fat was observed in cell-free extracts. Enterococcus faecium strains isolated from ewe milk and artisanal cheese from northwest Argentina present the metabolic potential to contribute to cheese flavour development.