Abstract
Algicidal bacteria offer an eco-friendly and promising approach for controlling harmful algae blooms (HABs). In this study, repeated batch fermentation of immobilized algicidal bacterium Vibrio brasiliensis H115 was preformed to enhance the productivity of the algicidal compounds. The highest algicidal efficiency of the fermentation products against Akashiwo sanguinea (100%) was achieved when the fermentation time was decreased from 24 to 14 h. The cell-free fermentation broth was then spray-dried and floating microcapsules were prepared from the dried powder. The optimum preparation conditions for floating microcapsules were: sodium alginate (SA), 3%; CaCO3: SA (mass ratio), 3:4; CaCl2, 3%; citric acid, 4%; ethylcellulose, 2%; crosslinking time, 30 min. Under the optimal conditions, the floating microcapsules displayed efficient A. sanguinea cell lysis ability and the algicidal efficiency increased from 10.62% (4 h) to 100% (24 h). These results suggest that the floating microcapsules could potentially be practically used for controlling the outbreaks of A. sanguinea.
Highlights
Red tides have attracted worldwide attention as they pose significant threats to fishery resources, marine ecosystems and human health (Anderson, 2009)
Repeated batch fermentation of immobilized bacteria has been widely applied for the production of secondary metabolites
The algicidal efficiency of the initial fermentation was compared to the repeated batch fermentation of the immobilized strain H115 (Figure 1)
Summary
Red tides have attracted worldwide attention as they pose significant threats to fishery resources, marine ecosystems and human health (Anderson, 2009). Algicidal bacteria, which are capable of algal cell lysis or growth inhibition have been isolated from lakes, estuaries, and seas. They offer a promising and eco-friendly biological approach for the control of harmful algae blooms (HABs) (Tian et al, 2012; Lu et al, 2016; Zheng et al, 2018). Algicidal bacteria and their associated metabolic products might result in a negative impact on other species and the ecosystem
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