Abstract: Bacterial diseases are among the primary constraints to marine fish aquaculture, which negatively impacting the health and economic viability of fish. Vaccines and paraprobiotics are being formulated as efficacious and sustainable alternatives to antibiotics in disease prevention and health management. Efficient inactivation of the bacterial pathogens without compromising their structural and immunogenic integrity is paramount to the formulation of such biological remedies. In this review, recent advances in methods of bacterial inactivation, including chemical treatments, ultrashort pulse lasers (USPL) , high hydrostatic pressure (HHP) , photodynamic inactivation (PDI) , and gamma irradiation, are addressed. Each method has its own advantages and limitations, indicating that a clear understanding of their mechanisms and uses is essential. Together, these novel methods have excellent potential for the improvement of bacterial control strategies in aquaculture systems. Future research needs to prioritize the optimization of these techniques for scale, safety, and regulatory compliance to enable broader application in marine fish farming. The incorporation of such technologies may lead to a resilient, more productive, and sustainable aquaculture industry.

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Abstract: The high permeability of silicone rubber is beneficial for use in membranes for pervaporation. In this study, pervaporation of hypochlorous acid (HOCl) was studied using a separation module containing a 6,000 silicone rubber (SR) hollow fiber membrane. Pervaporation experiments were conducted in a 1 m³ chamber. The membrane module was operated without using a vacuum pump, and the permeation of HOCl proceeded according to the solution-diffusion process. When weakly acidic (pH 5.0) hypochlorite solutions with concentrations of 100–1,000 mg/L were fed through the lumen of the SR hollow fiber membrane, the permeation of HOCl proceeded spontaneously under atmospheric pressure. During the operation of the membrane module, the concentration of gaseous hypochlorous acid (HOCl_(g)) in the chamber gradually increased and reached a steady state. The steady-state HOCl_(g) concentration increased as the concentration of undissociated hypochlorous acids (HOCl_(aq)) in the feed hypochlorite solutions increased. An exponential dependence of the steady-state HOCl_(g) concentration on the steady-state HOCl_(aq) concentration was observed. Operation of the SR hollow fiber membrane fed with weakly acidic hypochlorite solutions (i.e., 500 mg/L) in a 75 m³ room resulted in a uniform distribution of 7–10 ppb HOCl_(g), thereby exerting a moderate bactericidal effect against Staphylococcus aureus cells.

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Abstract: This study investigated the pervaporation of hypochlorous acid (HOCl) using a vacuum-driven process with a separation module containing 6,000 silicone rubber (SR) hollow fibers. Gaseous hypochlorous acid (HOCl_(g)) discharged from the membrane module was accumulated in a 1 m³ chamber. Weakly acidic (pH 5.0) hypochlorite solutions with free available chlorine (FAC) concentrations of 100–1,000 mg/L were fed through the lumen of the SR hollow fibers. Both the HOCl permeation rate and the steady-state HOCl_(g) concentration increased with the feed FAC concentration. When a 1,000 mg/L hypochlorite solution was used, the HOCl_(g) concentration in the chamber reached 5,500 ppb within 40 min. This accumulated HOCl_(g), when applied to microorganisms on wet agar plates at a concentration of approximately 320 ppb, achieved a >3-log reduction in viable bacterial cells within 10 min and fungal spores within 20 min. These results demonstrate that high-rate pervaporation of HOCl can be achieved using an SR hollow fiber membrane in a vacuum-driven process, and the resulting HOCl_(g) is effective for rapid disinfection.

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Abstract: Coptis chinensis is a traditional Chinese herb and the alkaloids in aqueous extract of C. chinensis are natural fungicides. The present study reports the inhibitory effect of aqueous extracts from five medicinal herbs on Nigrospora sphaerica. The aqueous extract of C. chinensis shows highest activity against N. sphaerica among these five herbs. The active alkaloids in aqueous extract of C. chinensis were identified and quantified. The results show that freeze-dried powder of aqueous extract of C. chinensis contains 46.62% berberine, 11.76% epiberberine, 15.88% coptisine, 13.26% palmatine and 3.86% jatrorrhizine. The additive effect among these alkaloids were also determined where the four-compound combination (epiberberine/coptisine/palmatine/berberine) exhibitsexhibits the best inhibitory effect. These findings highlight alkaloids from C. chinensis as promising eco-friendly alternatives to traditional fungicides for integrated pest management.

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