Fig. 3

Effect of proteinase K on the purified bacteriocin-like compound. The antimicrobial activity of the purified bacteriocin-like compound was determined as halo of growth inhibition of E. coli ATCC 25922 through the agar well diffusion assay. The Figure shows the lack of inhibition zone produced by the treatment of the bacteriocin-like compound by proteinase K (A); the inhibition halo produced by the no-treated bacteriocin-like compound after incubation at 37 °C and pH 7.5 (the proteinase K optimal pH) (B); the inhibition zone produced by the untreated bacteriocin-like compound at pH 2 (its optimal pH), as a positive control of the test (C); the lack of inhibition halo produced by the negative control NaCl 0.1 M pH 7.5 (buffer of the reaction with proteinase K) (D); and the lack of inhibition halo produced by the negative control NaCl 0.1M pH 2 (buffer for bacteriocin-like molecule activity) (E)