Evaluation of technological properties of Lactococcus lactis GU967439 isolated from uruguayan artisanal cheese

CARRO, SILVANA; LORENZO, G.; MERCANTI, DIEGO JAVIER; GONZÁLEZ REVELLO, A.; RAFFO, M.; QUIBERONI, ANDREA DEL LUJÁN; CALLIARI, A.; CAL, K.; REINHEIMER, JORGE ALBERTO

Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

Cerela

Sensory properties of artisanal cheeses made with rawmilk are mainly determined by the presence of autochthonous lactic acidbacteria (LAB). LAB cultures start milk acidification, contributing to milkcoagulation and, indirectly, to curd syneresis and cheese texture. Thesecultures are able to produce proteinases, peptidases and lipases, and have anassociated autolytic activity during ripening, all of which have a key role inflavor development. However, LAB could be affected by environmental factors,such as the presence of bacteriophages, which frequently alter fermentationprocesses and conduce to low quality final products. The aim of thiswork was to assess the technological properties of Lactococcus lactis GU967439, a native LAB strain isolated from artisanalcheeses manufactured in Colonia, Uruguay. Firstly, its acidifying activity wasevaluated through pH and titratable acidity measurements during growth curvesin sterile reconstituted skim milk (RSM). Growth at different NaClconcentrations (0-10 %) and at different pH values (4.3 to 5.5, adjusted withlactic acid) was evaluated, as well as production of diacetyl in milk.Autolytic activity of L. lactisGU967439 was determined after incubation at 30 °C for 24/48 h, whileextracellular proteolytic activity was assessed in milk agar. Moreover,lipolytic activity was qualitatively observed in two media with different fattyacid sources (Tween®80/milk cream). Thesensitivity of L. lactis GU967439 tonine phages isolated from Argentinian cheese plants and belonging to the INLAIN(Instituto de Lactología Industrial, Santa Fe, Argentina) bacteriophagecollection, was determined both in liquid (turbidity test) and solid (spottest) media. L. lactis GU967439showed low acidifying activity, reaching pH and acidity values of 5.39 and 35°D, respectively, after 30 h of incubation. While fast-acidifying LAB strainsare good candidates to be used as starter cultures, slow strains are suitableto be used as adjunct cultures, as long as they possess other interesting technologicalproperties. In this study, L. lactisGU967439 exhibited low tolerance to NaCl and lactic acid, displaying a growthreduction of more than 90% at the lowest NaCl concentration assayed. On theother hand, this strain produced diacetyl, and it was identified as Lactococcus lactis subsp. lactis biovar. diacetylactis. Autolytic activity was low and no lipolytic activitywas detected on the assayed media, but it showed proteolytic activity. L. lactis GU967439 displayed resistanceto all the phages tested. In conclusion, the diacetyl production, lowacidifying activity, lack of lipolytic activity and resistance to phages ofdairy origin make this strain suitable to be used as part of adjunct culturesat industrial scale.