Streptococcus macedonicus ACA-DC 198 produces the lantibiotic, macedocin, at temperature and pH conditions that prevail during cheese manufacture.

Streptococcus macedonicus ACA-DC 198, a natural cheese isolate, produces the anticlostridial bacteriocin, macedocin. Bacteriocin activity was detected from the mid-exponential growth phase and remained constant during the stationary phase. A secondary model was setup to describe the influence of temperature (20-45 degrees C) and pH (5.1-6.9) on cell growth of and bacteriocin production by S. macedonicus ACA-DC 198 during in vitro laboratory fermentations. The optimum temperature for bacteriocin production (20-25 degrees C) was markedly lower than the optimum growth temperature (42.3 degrees C). In contrast, the specific macedocin production was maximal around pH 6.0, whereas growth was optimal at pH 6.4. Consequently, the maximum bacteriocin activity was reached between pH 6.0 and 6.5.

Enterocin A production by Enterococcus faecium FAIR-E 406 is characterised by a temperature- and pH-dependent switch-off mechanism when growth is limited due to nutrient depletion.

The biokinetics of cell growth and bacteriocin production of Enterococcus faecium FAIR-E 406 was studied as a function of temperature (20-45 degrees C) and pH (5.5-8.5) using de Man-Rogosa-Sharpe medium. Growth of E. faecium FAIR-E 406 was characterized by three successive growth phases and was modelled with the mechanistic nutrient depletion model. Bacteriocin production showed primary metabolite kinetics but was limited to the early growth phase. The critical biomass for switching off bacteriocin production was dependent on medium pH and incubation temperature, and was inversely correlated with the specific bacteriocin production. Doubling the concentration of the nitrogen source as well as a step-wise pH increase shifted the bacteriocin production towards a higher switch-off cell density.

Macedocin, a food-grade lantibiotic produced by Streptococcus macedonicus ACA-DC 198.

Streptococcus macedonicus ACA-DC 198, a strain isolated from Greek Kasseri cheese, produces a food-grade lantibiotic named macedocin. Macedocin has a molecular mass of 2,794.76 +/- 0.42 Da, as determined by electrospray mass spectrometry. Partial N-terminal sequence analysis revealed 22 amino acid residues that correspond with the amino acid sequence of the lantibiotics SA-FF22 and SA-M49, both of which were isolated from the pathogen Streptococcus pyogenes. Macedocin inhibits a broad spectrum of lactic acid bacteria, as well as several food spoilage and pathogenic bacteria, including Clostridium tyrobutyricum. It displays a bactericidal effect towards the most sensitive indicator strain, Lactobacillus sakei subsp. sakei LMG 13558(T), while the producer strain itself displays autoinhibition when it is grown under conditions that do not favor bacteriocin production. Macedocin is active at pHs between 4.0 and 9.0, and it retains activity even after incubation for 20 min at 121 degrees C with 1 atm of overpressure. Inhibition of macedocin by proteolytic enzymes is variable.