Characterization of technological properties of Lactococcus lactis GU967439 isolated from Uruguayan artisanal cheese. POSTER

CALLIARI, A.; CAL, K.; REINHEMIER, J.; CARRO, S.; LORENZO, G.; GONZÁLEZ REVELLO, A.; MERCANTI, D.; RAFFO, M.; QUIBERONI, A.

San Miguel de Tucumán, Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

Centro de Referencia para Lactobacilos - CERELA

Sensory properties of artisanal cheeses are mainly determined by the presence of autochthonous lactic acid bacteria (LAB). LAB produce milk acidification, thus contributing to milk coagulation and indirectly, to curd syneresis and cheese texture. These cultures which are able to produce proteases, peptidases and lipases, play an important role in flavour development. Because many of these enzymes are intracellular, control and increase lysis (autolytic activity) are considered essential parameters to control and accelerate cheese ripening. However, LAB may be infected with bacteriophages, interfering with fermentation and yielding low quality products. The aim of this work was to assess some technological properties of Lactococcus lactis GU967439, a native LAB strain with antimicrobial activity (bacteriocin production) against Listeria monocytogenes, isolated from artisanal cheeses. Technological properties evaluated were: milk acidifying activity (pH and titratable acidity), tolerance to NaCl and lactic acid, production of diacetyl, autolytic activity and extracellular proteolytic and lipolytic activity. Additionally, the sensitivity to nine different phages was determined in both liquid (turbidity test) and solid media (spot test). Our results indicate that L. lactis GU967439 has low acidifying activity, reaching pH and acidity values of 5.39 and 35 OD respectively, after 30 h of incubation. Besides, L. lactis showed low tolerance to NaCl and lactic acid, showing a 90% growth reduction in the lowest concentration of NaCl evaluated (4.5 0/0). Growth fell more than 50 % at pH 5.5, 95% at pH 5.2 and there was no growth below pH 4.9. We found a low autolytic activity, being 14.5 and 14.7% at 24 and 48 hours, respectively. Also, while no lipolytic activity was detected, extracellular proteolytic activity in agar milk was present. On the other hand, this strain produced diacetyl, so it was identified as Lactococcus lactis subsp. lactis bv. diacetylactis. Finally, the native strain did not show sensitivity to any of the bacteriophages evaluated. In conclusion, because this native strain did not show rapid acidification capacity, it may result a suitable adjunct culture. Moreover, since it demonstrated other interesting properties such as bacteriocins and diacetyl production, as well as resistance to some bacteriophages, this strain could be attractive for the dairy industry.