A Membrane-Free Alternative Method for Concentration of Live Microorganisms by Foam Separation

The collection and isolation of microorganisms from seawater in aquaculture systems, aquariums, fishing port facilities, and recreation areas is the most fundamental means of studying microbiological, physiological, and pathogenic properties of water to improve public health and the environment. However, there are few methods for concentration of living microorganisms. Thus, it is necessary to develop a technology for collection and concentration of microorganisms from seawater. In this study, we examined the removal and concentration of the bacterium Vibrio and fungus Fusarium from seawater by foam separation using dispersed bubbles and surfactants. After batch processing with only 1 mg/L milk casein added as a surfactant and after injection of bubbles, Vibrio and Fusarium were isolated at removal efficiency rates of more than 80% and 99.9%, respectively, and most of the microbial cells were concentrated alive in the foam water within 5 min. When the continuous foam separation unit was installed at the actual site of a fishery harbor, though the removal efficiency for viable bacteria was 49.2%, the bacteria were isolated at a huge concentration in the foam water, and the concentration factor was 18.5. Foam separation is a feasible convenient technology for not only seawater purification but also membrane-free concentration of live microorganisms.

Keywords: Concentration, Dispersed bubbles, Fusarium, Live state, Milk casein, Removal, Seawater, Vibrio.