Production and Physico-chemical Characterization of Bacteriocins-like Inhibitory Substances from Marine Bacterium ZM81

The significant bacteriocinogenic marine strain ZM81 (Gram positive pleomorphic rods), was isolated from open sea region of Karachi coast producing Bacteriocins or/and Bacteriocins-like Inhibitory Substances (BLIS). Cell Free Neutralized Supernatant (CFNS) of this strain exhibited activity within a wide pH range of 4-12. CFNS retained its bioactivity up to 60?C (for 30 min); hence it is heat-labile. The agar concentration of 1.2-1.6% was found optimum for the maximum zone of inhibition in Zobell`s medium. The bacteriocin was sensitive to pronase and trypsin as the activity was partially lost after enzymes treatment. The results indicate the proteinaceous nature of the inhibitory substance and hence could be classified as bacteriocins or/and Bacteriocin-like Inhibitory Substances (BLIS). The maximum zone of inhibition (46 mm) was exhibited at 2.5% of NaCl concentration and very little residual bioactivity was found in the absence of NaCl in Zobell`s medium. The results suggest that the presence of NaCl is critical for the production of bacteriocin by this strain. The maximum zone of inhibition (bacteriocinogenesis) was found in Zobell`s medium. The preparation was found sensitive to different organic solvents (acetone, methanol, ethanol, heptane, chloroform) and surfactants (SDS and EDTA). A slight residual activity was found after propanol and Triton-X-100 treatments; suggesting slight resistance of this bacteriocin to these treatments. Further, a preliminary fractionation of the CFNS through the membrane of 10 kDa cut-off enhanced the activity in>10 kDa fraction suggesting the high molecular mass nature of the active substance, a characteristic feature of marine bacteriocins.