Impact of Nisin and Nisin-Producing Lactococcus lactis ssp. lactis on Clostridium tyrobutyricum and Bacterial Ecosystem of Cheese Matrices

Abstract

<i>Clostridium tyrobutyricum</i> spores survive milk pasteurization and cause late blowing of cheeses and significant economic loss. The effectiveness of nisin-producing <i>Lactococcus lactis</i> ssp. <i>lactis</i> 32 as a protective strain for control the <i>C. tyrobutyricum</i> growth in Cheddar cheese slurry was compared to that of encapsulated nisin-A. The encapsulated nisin was more effective, with 1.0 log₁₀ reductions of viable spores after one week at 30 °C and 4 °C. Spores were not detected for three weeks at 4 °C in cheese slurry made with 1.3% salt, or during week 2 with 2% salt. Gas production was observed after one week at 30 °C only in the control slurry made with 1.3% salt. In slurry made with the protective strain, the reduction in <i>C. tyrobutyricum</i> count was 0.6 log₁₀ in the second week at 4 °C with both salt concentration. At 4 °C, nisin production started in week 2 and reached 97 µg/g after four weeks. Metabarcoding analysis targeting the sequencing of 16S rRNA revealed that the genus <i>Lactococcus</i> dominated for four weeks at 4 °C. In cheese slurry made with 2% salt, the relative abundance of the genus <i>Clostridium</i> decreased significantly in the presence of nisin or the protective strain. The results indicated that both strategies are able to control the growth of <i>Clostridium</i> development in Cheddar cheese slurries.