Antimicrobial activity of Lactobacillus plantarum strains isolated from different environments: A preliminary study

The aim of this study was the investigation of the antimicrobial activity expressed by Lactobacillus plantarum strains isolated from different fermented matrices (wines, cheese, fermented sausages, and sourdoughs). A total of 106 strains of Lb. plantarum (producers) were tested against 33 undesirable microorganisms (indicators), including both moulds and bacteria. The antimicrobial activity exerted by growing cells (GC) was evaluated by the spot-on-thelawn, while the activity of cell free supernatants (CFS), neutralised CFS (nCFS) and CFS treated with proteases (pCFS) was assessed by the agar well diffusion assay. The antagonistic effect produced by GC of Lb. plantarum isolated from wines was higher than that exibited by cells isolated from other fermented matrices. Moreover, 5 CFS - all from wine strains - as well as the corresponding nCFS and pCFS were able to inhibit different bacteria and moulds. The results suggested a relationship between the origin of Lb. plantarum strains and their antimicrobial properties, while no relation was found between the intensity of inhibition and the origin of indicator strains. This fact highlights that the knowledge of conditions characterising different ecosystems can be helpful in the detection and isolation of Lb. plantarum strains to be used as protective agents.