David D. Kuhn

Effect of Common Aquaculture Chemicals against Edwardsiella ictaluri and E. tarda

Edwardsiellosis is an important bacterial infection of freshwater and marine fishes. Edwardsiella ictaluri causes enteric septicemia of catfish, and E. tarda causes emphysematous putrefactive disease of catfish and fish gangrene in various species; these diseases have considerable economic effects on the aquaculture industry. In addition, E. tarda is an important zoonotic pathogen. Thus, the reduction or elimination of these pathogens from an aquarium or aquaculture facility is imperative. This study examined a variety of commercially available chemicals for their ability to reduce or eliminate E. ictaluri and E. tarda from the aquatic environment. The various concentrations of chemicals were tested in vitro in microcentrifuge tubes with a known concentration of bacteria at room temperature. In this study, ethyl alcohol (30, 50, or 70%), benzyl-4-chlorophenol/phenylphenol (1%), sodium hypochlorite (50, 100, 200, or 50,000 mg/L), n-alkyl dimethyl benzyl ammonium chloride (1:256), povidone iodine (50 or 100 mg/L), glutaraldehyde (2%), and potassium peroxymonosulfate/sodium chloride (1%) were effective disinfectants, as each reduced or eliminated the number of detectable organisms within 1 min of contact time. However, neither Chloramine-T (15 mg/L) nor formalin (250 mg/L) substantially reduced bacterial counts even after 60 min of contact time.

SDE and SPME Analysis of Flavor Compounds in Jin Xuan Oolong Tea.

Simultaneous distillation-extraction (SDE) and solid phase micro extraction (SPME) are procedures used for the isolation of flavor compounds in foods. The purpose of this study was to optimize SDE conditions (solvent and time) and to compare SDE with SPME for the isolation of flavor compounds in Jin Xuan oolong tea using GC-MS and GC-O. The concentration of volatile compounds isolated with diethyl ether was higher (P < 0.05) than for dichloromethane and concentration was higher at 40 min (P < 0.05) than 20 or 60 min extractions. For SDE, 128 volatiles were identified using GC-MS and 45 aroma active compounds using GC-O. Trans-nerolidol was the most abundant compound in oolong tea. The number of volatiles identified using GC-MS was lower in SPME than SDE. For SPME, 59 volatiles and 41 aroma active compounds were identified. The composition of the volatiles isolated by the 2 methods differed considerably but provided complementary information.

Changes in flavor volatile composition of oolong tea after panning during tea processing

Abstract Panning is a processing step used in manufacturing of some varieties of oolong tea. There is limited information available on effects of panning on oolong tea flavors. The goal of this study was to determine effects of panning on flavor volatile compositions of oolong using Gas Chromatography‐Mass Spectrometry (GC‐MS) and Gas Chromatography‐Olfactometry (GC‐O). SDE and SPME techniques were applied for extraction of volatiles in panned and unpanned teas. A total of 190 volatiles were identified from SDE and SPME extractions using GC‐MS and GC‐O. There were no significant differences (P > 0.05) in aldehyde or terpene contents of unpanned and panned tea. However, alcohols, ketones, acids and esters contents were significantly reduced by panning. Among 12 major volatiles previously used for identification and quality assessment of oolong tea, trans nerolidol, 2‐ hexenal, benzaldehyde, indole, gernaiol, and benzenacetaldehyde contents were significantly decreased (P < 0.05) by panning. Panning increased (P < 0.05) contents of linalool oxide, cis jasmone, and methyl salicylate. The GC‐O study also showed an increase of aroma active compounds with sweet descriptions and decrease of aroma active compounds with fruity and smoky descriptions after panning. Panning significantly changes the volatile compositions of the tea and created new aroma active compounds. Results from this study can be used in quality assessment of panned oolong tea.

Efficacy of Common Aquaculture Compounds for Disinfection of Flavobacterium columnare and F. psychrophilum

Flavobacterium columnare and F. psychrophilum are important pathogens of the aquaculture industry, and thus disinfection of aquaculture systems and equipment is essential for disease control. This study examined commercially available compounds in vitro for their ability to eliminate these two species of Flavobacterium from the water. The compounds evaluated included Clorox, ethanol, Roccal, Lysol, iodine, formalin, Chloramine-T, glutaraldehyde, potassium permanganate, sodium chloride, and Virkon Aquatic. In this study, 70% ethanol, 50% ethanol, Clorox, Roccal, Lysol, iodine, glutaraldehyde, Chloramine-T, and Virkon Aquatic reduced the number of bacteria of both species to zero within one minute of contact time. Formalin and 30% ethanol also killed both species of bacteria, but required a longer contact time. Potassium permanganate killed F. columnare within one minute, but did not reduce the numbers of F. psychrophilum even after one hour of contact time. Sodium chloride was not effective.

Postharvest transfer and survival of Salmonella enterica serotype enteritidis on living lettuce

The potential for postharvest transfer of Salmonella to ‘living lettuce’ is not well understood. In this study, the transfer of Salmonella enterica Enteritidis (6 log CFU g−1) from worker hands or contaminated roots to leaves of living lettuce was quantified. Transfer rates of Salmonella from contaminated gloves to sequentially handled lettuce heads ranged from 94% to head 1, 82% to head 2 and 69% to head 3. On average, 2·9 ± 0·1 log CFU g−1 (64%) Salmonella was transferred from inoculated roots to leaves resulting from typical postharvest handling activities for living lettuce. Salmonella persisted on leaves stored at recommended storage temperatures (4°C) and increased 0·5 log CFU g−1 when stored at temperature abuse conditions (12°C). Salmonella increased 1·6 log CFU g−1 on roots after 18‐day storage at 12°C, emphasizing the need to maintain temperature control to reduce the risk of human illness.

Analysis of microcystin-LR and nodularin using triple quad liquid chromatography-tandem mass spectrometry and histopathology in experimental fish

&NA; Microcystins (MCs) are hepatotoxic cyanobacterial metabolites produced sporadically in aquatic environments under favorable environmental conditions. Affinity of these toxins to covalently bind with protein phosphatases poses a challenge in their detection. Lemieux oxidation to release 2‐methyl‐3‐methoxy‐4‐phenylbutyric acid (MMPB), a common moiety to all MCs congeners, has been used in detection of these compounds, however a lack of sensitivity has limited the usefulness of the method. In this study, modifications of the oxidation and solid phase extraction procedures, combined with a sensitive LC/MS/MS (liquid chromatography/mass spectrometry) detection, have resulted in 25 ng/g method detection limits in both liver and plasma samples. Samples harvested from six fingerling channel catfish (Ictalurus punctatus) dosed intraperitoneally with a sublethal MC‐LR dose of 250 &mgr;g/kg were analyzed, and microcystin concentrations ranging from 370 to 670 ng/g in plasma and 566–1030 ng/g in liver were detected. Similarly, 250 &mgr;g/kg nodularin‐dosed channel catfish fish were found to contain 835–1520 ng/g in plasma and 933–1140 ng/g in liver. Detection of the toxins in serum and liver combined with the presence of histopathological lesions consistent with these hepatocellular toxin in exposed fish and no positive findings in the control fish demonstrates the usefulness of this analytical procedure for the diagnosis of suspected algal toxicity cases. HighlightsHistopathological lesions and residues of MC‐LR and Nodularin in plasma and liver.Hepatocellular necrosis with karyomegaly and peripheralized chromatin.Lemieux oxidation generated MMPB from samples for analysis with LC/MS/MS.Method detection limit was established at 25 ng/g in liver and plasma.

Production of omega-3 enriched tilapia through the dietary use of algae meal or fish oil: Improved nutrient value of fillet and offal

The goal of this project was to increase the nutrient value of fillets, by-product muscle, and offal of aquacultured tilapia. A diet that includes seafood with a high omega-3 (n-3) fatty acid content, more specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are known to have numerous health benefits for consumers. Improved nutrient value of the offal may also attract new market opportunities for the aquaculture industry. Tilapia were cultured on different experimental feeds that contained various levels of n-3 fatty acids from either fish oil (FO) or algae meal (AM) that were used to replace corn oil. The experimental diets included a control (corn oil 6.3%), FO1%, FO3%, FO5%, AM1.75%, AM5.26%, and AM8.77%. All diets were formulated to be isocaloric, isonitrogenous, and isolipid. Three hundred and fifty tilapia with an initial mean weight of 158±2 g were cultured in a recirculating aquaculture system (seven diets replicated at the tank level, 14 tanks, 25 fish per tank). For all of the production performance data, no differences (P>0.05) were observed between the experimental groups which included survival (overall mean ± standard error, 99.4±0.3%), growth per week (45.4±1.0 g/wk), food conversion ratio (1.32±0.03), fillet yield (44.4±0.2%), hepatosomatic index (1.61±0.02), viscerosomatic index (2.86±0.06), and mesenteric fat index (0.97±0.04). Fillet and rib meat tissues were collected at weeks four and eight, and liver and mesenteric fat tissues were collected at week eight. Fatty acids were extracted, methylated and identified with gas chromatography–mass spectrometry. All tissues had improved fatty acid profiles (higher n-3, lower n-6, n-6:n-3) with increasing levels of FO and AM in the diet. For example, the best diet for significantly (P<0.05) improving the lipid profile in tilapia fillets at week eight was diet AM8.77%. In the fillet, total n-3 was increased (control versus AM8.77%) from 151.2±19.0 to 438.7±14.2 mg per 4 ounce (113 g) serving and n-6:n-3 ratio was improved from 5.19±0.76 to 1.29±0.03.

Modulation of innate immunity in Nile tilapia (Oreochromis niloticus) by dietary supplementation of Bacillus subtilis endospores

Abstract Dietary supplementation of probiotics is growing as a scientifically valid alternative to antibiotics for enhancement of overall animal health and productivity in aquaculture. Strains of Bacillus subtilis are regarded as attractive probiotic candidates to the fish farming industry; however, there is a limited number of studies focused on the use of specific strains probiotics in tilapia, and therefore complicating replication. The objective of this study was to examine the effect of the strains NZ86 (NRRL B‐50136) and O14VRQ (NRRL B‐67221) of B. subtilis on various parameters of the innate immunity in Nile tilapia (Oreochromis niloticus) in a 51‐day feeding trial. Supplementation of tilapia with either strain resulted in significant increases (p < 0.05) in plasma lysozyme concentration of varying degrees throughout the trial. Meanwhile, alternative complement activity was significantly elevated (p < 0.05) only after feeding of the NZ86 strain after 14 and 51 days. Conversely, supplementation with O14VRQ resulted in a significant increase (p < 0.05) in the percent of neutrophils in the peripheral blood of tilapia by day 28. At the end of the trial, there was a trend towards increased phagocytic and respiratory burst activities observed in immune organ derived leukocytes. Feeding with either probiotic appeared to have an up‐regulation on the gene expression of both pro‐inflammatory cytokines in the intestine, yet only O14VRQ was significantly different than the control. Moreover, the occurrence of these results could be associated with supplementation of the probiotic strains, given that Bacillus bacteria were observed to populate the intestines of the dietary treatment groups. These results suggest the potential roles of these B. subtilis probiotic candidates to stimulate immune responses both locally and systemically in tilapia. HighlightsDietary Bacillus subtilis NZ86 enhanced multiple innate immune responses in tilapia.Dietary B. subtilis O14VRQ stimulated several innate immune responses in tilapia.Immune responses were associated with presence of bacterial strains in the gut.Dietary B. subtilis O14VRQ up‐regulated gut levels of pro‐inflammatory cytokines.

Adsorptive performance of granular activated carbon in aquaculture and aquaria: a simplified method

ABSTRACT A principle concern for aquaculturists and aquarium hobbyists is the control and removal of dissolved organic matter. Granular activated carbon is a well-established medium for the adsorption of dissolved organic substances associated with these issues. The selection of activated carbon for aquaria and aquaculture is not well established due to innate heterogeneity of these waters. The means to completely characterize adsorption between carbon sources are generally not available to end users provided their level of expertise and/or resources at their disposal. This study introduces a relatively simple method for characterizing activated carbon quality and filter performance utilizing readily available and relatively safe indicator compounds to test adsorptive capabilities between different sources of granular activated carbon. Methylene blue and a commercial mix of humic and tannic substances were used to comparatively test adsorptive performance between two filter groups (i.e., sources of granular activated carbon) by tracking spectral absorbance with nonlinear regression statistics and validating removal trends against mature aquaculture water. Greater adsorptive capacities were consistently observed in one filter group throughout the indicator testing battery. Similar findings were observed between the two indicator tests, thereby confirming the method. This method can be adopted by commercial aquaculture operations or aquarists to assist in comparatively screening particular types, particle sizes, and sources of granular activated carbon for specific water quality and engineering requirements.