Effect of Certain Food Additives on Lactococcus lactis Strains Intended to be Used for Dairy Food Fermentation

The aim of this study was to evaluate the resistance of five Lactococcus lactis strains (LL19, LL21, LL30A, LL57A, and LL77) isolated from cow’s milk to food additives commonly used in the food industry: sodium benzoate, lysozyme, and nisin. The resistance of L. lactis strains to sodium benzoate (concentrations (0.075–1%)) was determined by viable cell count and spectrophotometric examination; to lysozyme—by viable cell counts after different time intervals; and to nisin—using the well diffusion method on MRS agar with seven different nisin concentrations (2 - 150 μg/mL).

The sodium benzoate experiment showed that strain LL57A exhibited the highest resistance—at all concentrations, growth activity remained above 63%, reaching up to 80% at the 0.075% concentration. The lowest resistance was observed in strain LL77—growth decreased to 47% at the 1% concentration.

The lysozyme experiment showed that LL21 and LL19 strains maintained high viability even after 24 hours (8.90 and 7.85 log CFU/ml, respectively).

The nisin experiment showed that strain LL77 exhibited the highest resistance, while LL19 was the most sensitive.

Strains LL57A and LL21 demonstrated the highest resistance to most of the tested additives and have potential for use in fermented dairy products containing preservatives.