Detection of the bacteriocin propionicin PLG-1 with polyvalent anti-PLG-1 antiserum

Polyclonal antibodies against the bacteriocin propionicin PLG-1 were produc ed in rabbits at high titer (256,000 to 512,000, as determined by indirect enzyme-linked immunosorbent assay [ELISA]). Anti-PLG-l antiserum neutralize d the antimicrobial activity of PLG-1 preparations in a well diffusion assa y. Cross-reacting protein was detected using an indirect ELISA of the cultu re supernatant from a fed-batch fermentation of the producer strain Propion ibacterium thoenii P127 within the first 24 h of incubation, but bacterioci n activity was not detected in the same culture until 217 h of incubation. Culture supernatants from 156 strains of classical dairy propionibacteria m ere tested by indirect ELISA at 5 and 12 days of incubation for production of cross-reacting protein and by well diffusion assay for bacteriocin activ ity. Cross-reacting protein was detected in 52 strains: all of the tested s trains of P, thoenii, most of the strains of Propionibacterium jensenii, an d a minority of the Propionibacterium acidipropionici and Propionibacterium freudenreichii strains. Of these 52 strains, only 4 strains of P. thoenii showed bacteriocin activity in a well diffusion assay. Eight bacteriocin-ne gative mutants of strain P127 were negative in both ELISA and well diffusio n assays, Western blot analysis showed that three protein bands bound anti PLG-1 antibodies in culture supernatants: a 9.1-kDa band that is assumed to be the PLG-1 monomer and 16.2- and 27.5-kDa bands that may be precursors, multimers, or complexes of PLG-1.