Abstract
The antimicrobial efficacy of novel photodynamic inactivation and nanobubble technologies was evaluated against Vibrio parahaemolyticus and Aeromonas hydrophila as two important aquatic microbial pathogens. Photodynamic inactivation results showed that LED (470 nm) and UV-A (400 nm)-activated curcumin caused a complete reduction in V. parahaemolyticus at 4 and 22 °C, and a greater than 2 log cfu/mL reduction in A. hydrophila, which was curcumin concentration-dependent (p < 0.05). Furthermore, the photodynamic approach caused a greater than 6 log cfu/mL V. parahaemolyticus reduction and more than 4 log cfu/mL of A. hydrophila reduction in aquaponic water samples (p < 0.05). Our results with the nanobubble technology showed that the nanobubbles alone did not significantly reduce bacteria (p > 0.05). However, a greater than 6 log cfu/mL A. hydrophila reduction and a greater than 3 log cfu/mL of V. parahaemolyticus reduction were achieved when nanobubble technology was combined with ultrasound (p < 0.05). The findings described in this study illustrate the potential of applying photodynamic inactivation and nanobubble–ultrasound antimicrobial approaches as alternative novel methods for inactivating fish and shellfish pathogens.
Highlights
Fisheries and aquaculture are a growing industry, and seafood consumption has been increased from an average of 9.9 kg per capita in the 1960s, to 20.3 kg per capita in 2017 [1]
Our preliminary experiments showed that nanobubbles produced by pure oxygen showed stronger antibiofilm and antimicrobial properties as compared to nanobubbles generated by pure carbon dioxide or air
The results indicated that V. parahaemolyticus was less resistant to light-activated curcumin compared to A. hydrophila
Summary
Fisheries and aquaculture are a growing industry, and seafood consumption has been increased from an average of 9.9 kg per capita in the 1960s, to 20.3 kg per capita in 2017 [1]. Controlling zoonotic fish diseases and foodborne pathogens in recirculating aquaculture systems and aquaponics using antibiotics, chemical sanitizers, and pesticides, is challenging due to the sensitivity of the microbial community in biofilters which oxidize ammonia to nontoxic nitrate, chemical residue concerns in both fish and plants, and regulatory stand points. These challenges motivated researchers to develop novel chemical-free, or bio-based antimicrobial approaches. This study illustrates the potential of light activated food grade antimicrobial materials, such as curcumin, and a novel chemical-free approach combining nanobubbles and ultrasound for water sanitation in intensive RAS and aquaponics systems to reduce reliance on chemical-based approaches
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