Isolation and Identification of Proteolytic Lactic Acid Bacteria from Regional Dairy Products

CAROL, JUAN J.; TARGA S; IBARRA M; OVEJERO M; LEDESMA, ANA E.; BUSTOS, ANA Y.

Encuentro; LI Reunion Anual de la sociedad Argentina de Biofisica; 2023

and prevent digestive diseases. These desirable properties are attributed, in part, to themetabolic processes of lactic acid bacteria (LAB) that possess enzymes such as proteasesthat enhance protein digestibility and improve the organoleptic characteristics of theproducts. The first objective of this work was to isolate and identify LAB strains fromregional dairy products and select those with proteolytic activity and secondly toinvestigate the subcellular location of the enzymes. Fifty-seven strains were isolated fromartisanal goat and cow cheeses, as well as goat milk and whey cheese and identifiedthrough MALDI-TOF Mass Spectrometry. The dominant species identified wasEnterococcus faecium (56.14 %), wich was found mainly in goat milk. Additionally, otherspecies such as Lctiplantibacillus plantarum/paraplantarum/pentosus (24.56 %),Lactococcus garvieae (3.51 %), Enterococcus durans (1.75 %), Lactococcus lactis (1.75%) were found (3.51 %).The qualitative test of proteolytic activity was performed using 1 % Skim Milk Agar (SMA)plates. Strains showing a hydrolysis halo around the colonies were considered positive. Inaddition, different fractions (extracellular, intracellular and non-proliferating cells) wereevaluated in the presence of casein for 2 h at 37°C. The activity was observedpredominantly in the extracellular fraction of cells cultured in MRS broth supplementedwith calcium chloride relative to conventional MRS, reaching an amino acid concentrationof 38.31 mmol glycine/L.The characterisation of LAB strains with high enzymatic activity is of potentialbiotechnological importance in fermentative processes and human health, as they canimprove the physicochemical characteristics of foods and release bioactive molecules.