How we can improve the antimicrobial performances of lactic acid bacteria? A new strategy to control Listeria monocytogenes in Gorgonzola cheese

This study was aimed to evaluate the effectiveness of two lactic acid bacteria (LAB) cultures (Lactococcus lactisFT27 and Carnobacteroim divergens SCA), lactic acid/sodium lactate (LASL - L-lactic acid 61% (w/w) and Lsodiumlactate 21% (w/w)) and their combination against four Listeria monocytogenes biotypes isolated fromGorgonzola cheese. In vitro antilisterial activity showed that the sensitivity to antimicrobials was strain-dependent.Antimicrobial challenge testing was performed on Gorgonzola rinds simulating contamination occurringat the beginning (6 days) and at the end (55 days) of the ripening period, to assess the antilisterial activity ofLAB strains and LASL during the subsequent 60 days at 4 °C. LASL showed a higher antilisterial activity thanLAB, maintaining the pathogen content below the EC limit (< 2.0 log10 CFU/g) for 60 days. A strong listericidaleffect was observed combining LAB with LASL (2,8 ?L/cm2) Lc. lactis in combination with LASL completelyinhibited the two L. monocytogenes strains in the first 50 days, while LASL with C. divergens was more effective inthe second part of ripening when the pH raised. Data obtained encourage the use of LASL along with antimicrobialLAB rotation schemes during cheese ripening for the prevention and/or control of the L. monocytogeneson cheese surface.