CONICET | Buscador de Institutos y Recursos Humanos

Bacteriocins are proteinaceous antimicrobials that inhibit the growth of bacterial strains phylogenetically related to the producing strain, whose interest lies in their potential for application in the food industry, medicine, or agriculture. Rhizospheric strain Pseudomonas fluorescens SF4c produces phage-tail-like bacteriocins (tailocins) with activity against phytopathogenic strains of the genera Pseudomonas and Xanthomona. In general, the bacteriocin expression can be increased by treatments that cause DNA damage, such as UV irradiation or mitomycin C. However, the protocols must be set-up for each particular strain in order to find the highest bacteriocins titers. The aim of this work was to optimize the tailocin production in P. fluorescens SF4c. For this, cultures of strain SF4c were induced with UV or mitomycin C and different conditions were tested, such as exposure time (or concentration) and induction at different optical densities of culture. The higher titers of bacteriocin were reached when cultures at optical density of 0.5 were irradiated for 20 seconds with UV at 254 nm. On the other hand, bacteriocin production was also increased when 6 μg mL1 mitomycin C were added to a culture at optical density of 0.5. For potential application of tailocin SF4c, this must be produced on a large scale and properly concentrated without losing antimicrobial activity. Therefore, the storage of the tailocins at -20°C (the first stage before lyophilization) and lyophilization process was also evaluated. Different protectors such as reconstituted skim milk and sucrose were used. The bacteriocins were stable at -20°C. The lyofilization during 72 h reduced the activity of tailocins. However, the antimicrobial activity was maintained when the lyophilization time was 19 h and skim milk was used as protector. This study provides useful information for the formulation of bacteriocin as bioinput to be applied in agriculture in the future.