Objective: In this study, cell extract of Bdellovibrio bacteriovorus, a Gram-negative predator bacterium that feeds on other gram negative bacteria was investigated for its potential for eradicating or inhibiting biofilm formation by active wastewater bacteria.

Material and Methods: The effect of several pH, temperature and mineral concentrations on the activity of B. bacteriovorus was investigated. The inhibition effect of B. bacteriovorus cell extract on biofilm formation by wastewater bacteria was measured by crystal violet method using 96 well polystrene plates. Cleaning effect of cell extracts of B. bacteriovorus on biofilm layer formed on filtration membrane was measured by using fouled membrane and dead- end reactor system.

Results: It was found that 8-8.8 pH, 29.5°C temperature and mineral concentrations of 5 mM CaCl₂, 0.1 mM MgCl₂ are optimum for B. bacteriovorus to acquire highest activity. The effect of B. bacteriovorus cell extract to inhibit the biofilm formation by sludge bacteria was measured to be 39%. When the biofilm layer accumulated on the surface of filtration membrane used for wastewater filtration was cleaned by B. bacteriovorus cell extract, an improvement of 12.44 L.m-2.sa-1 was observed in the flux of membrane as compared to the control that was cleaned by buffer.

Conclusion: The results show that B. bacteriovorus cell extract which is rich in lytic enzymes can be used for inhibition or cleaning of undesired biofilm layer formed on different surfaces.