Aims: To evaluate the interactions of Staphylococcus xylosus on Kocuria varians strains isolated from fermented meat products.
Methods and results: Interactions were assessed in vitro by agar spot test, agar well diffusion assay and spectrophotometric assay. The growth of K. varians (five strains) alone was compared with that in the presence of growing cells of S. xylosus (50 strains) or in the presence of heat-treated or untreated supernatants of S. xylosus. Sixteen strains stimulated the growth of K. varians K4, while four strains inhibited the K4 strain. Heated cell-free supernatants of S. xylosus did not have any effect on K. varians. The proteolytic activity of single strains or their combinations was assessed in vitro and in vivo by sodiumdodecylsulfate-polyacrylamide gel electrophoresis of sarcoplasmic protein extracts. Combinations of stimulatory strains of S. xylosus and K. varians showed a higher proteolytic activity compared with that of S. xylosus or K. varians alone.
Conclusions: The interactions between strains may influence both the growth of the co-cultured strains and proteolysis, technologically relevant characteristics.
Significance and impact of the study: The study of interactions between coagulase-negative cocci may guide the formulation of mixed strain starters for the production of fermented sausages.