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.