Autolysis of Lactococcus lactis ssp. lactis and Lactobacillus casei ssp. casei. Cell lysis induced by a crude bacteriocin

Autolytic properties of Lactococcus lactis subsp. lactis IFPL359, its Lac− Prt− derivative Lc. lactis T1 and Lactobacillus casei subsp. casei IFPL731, used as starter and adjunct starter in goatʹs milk cheese making, have been studied. The lytic effect of a bacteriocin produced by a lactic acid bacterium isolated from raw goatʹs milk has also been analyzed. Lactococcal cells resuspended in phosphate buffer showed a peak of autolysis when they were harvested in the early growth phase. A more stable autolytic pattern through the exponential growth was obtained for Lb. casei IFPL731. Optimal autolysis was found in 0.1 M sodium phosphate buffer during incubation at 40°C for Lb. casei IFPL731 and at 35°C for the lactococci. Thermoinduction of cell lysis was not obtained in any of the cases under the conditions studied. Lytic effect of the crude bacteriocin assayed was strongest against Lc. lactis T1. Lysis response to the bacteriocin seemed to be strain-dependent and related to growth conditions.