Comparative characterization of novel strains of Lactococcus lactis subsp. lactis obtained by the protoplast fusion technique

The morphological, cultural, physiological, and biochemical properties of novel efficient nisin-producing strains of Lactococcus lactis subsp. lactis were studied. These strains, which were obtained by fusion of the protoplasts of allied parental strains with low nisin-producing activities, turned out to be similar to their parents in morphology and cultural properties but differed from them in carbohydrate fermentation patterns, requirements for growth factors (amino acids, purines, pyrimidines, and vitamins), and sensitivity to antibiotics. The novel strains enriched the collection of efficient producers of nisin, a widely used food preservative.