| Summary: | 碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 100 === This study evaluated the efficacies of nanosilver solution (2000 ppm) and nanosilver non-woven fabric applied in aquaculture. The MIC value of nanosilver against Vibrio alginolyticus was 8 ppm; the MBC value was 16 ppm. Nanosilver of 2000 ppm could produce bacteriostatic circles against Vibrio alginolyticus, Vibrio parahaemolyticus, Aeromonas hydrophila and Edwardsiella tarda growth in TSA, with diameters of 14.0 ± 2.0, 14.0 ± 1.5, 7.5 ± 2.5 and 14.5 ± 2.0 mm, respectively. When V. alginolyticus or V. parahaemolyticus reached a bacterial count of 103 CFU/mL in seawater, treatment with 8 ppb nanosilver for 2 hours or 1/2 hour had a complete bacteriostatic effect; when the bacterial count increased to 105 CFU/mL, treatment time with the same concentration increased to 4 and 1 hour. When A. hydrophila or E. tarda reached a bacterial count of 103 CFU/mL in freshwater, treatment with 1 ppb nanosilver for 1/2 hour or 2 hours had a bacteriostatic effect; when the bacterial count increased to 105 CFU/mL, treatment with 2 ppb for 1/2 hour was effective.
In the experiment to find the bacteroistatic effect of nanosilver in different salinities of seawater, 15 and 25 ppt seawater which contained 103 CFU/mL V. alginolyticus were treated with 8 ppb nanosilver, and the bacteriostatic effects could last for 2 days; when the salinity was increased to 35 ppt, the effect could only last for 1 day. When the nanosilver concentration was increased to 16 ppb, the effect could last for 4 days in 35 and 25 ppt seawater, and for 5 days in 15 ppt seawater. This experiment also confirmed that nanosilver, less than 16 ppb, would not affect the ammonia-nitrogen, nitrite, dissolved oxygen, pH or redox potential in aquaculture water.
In the disinfectant experiment on live feeds, treatment of 16 ppb nanosilver on Brachionus plicatilis for 15 minutes could maintain their vitality and has a good bacteriostatic effect; however, nanosilver was unsuitable to be used for disinfection of Isochrysis galbana. Feeding diets supplemented with 800 ppb nanosilver to Epinephelus coioides for 8 weeks would not affect their growth or survival; nanosilver would not remain in the muscle tissues, but would remain in the liver, intestines, brain, and head kidney. Also, treatment with 25 ppb nanosilver on Acanthopagrus sivicolus fertilized eggs for 10 minutes could result in bacteriostasis, and their hatchability would not be affected.
15 grams of nanosilver non-woven fabric was used as a filter material to treat seawater contained 103 CFU/mL V. alginolyticus, at a water flow rate of 5 ± 0.5 mL/sec. After one filtration process, 50% of the bacteria could be diminished; after four processes, 75% could be diminished. This study assessed that nanosilver and nanosilver non-woven fabric were usable in aquaculture as a bacteriostatic supplement and as a filter material.
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