Within the food-producing sectors, aquaculture is the one that has developed the greatest growth in recent decades, currently representing almost 50% of the world's edible fish. The diseases can affect the final production in intensive... more
Within the food-producing sectors, aquaculture is the one that has developed the greatest growth in recent decades, currently representing almost 50% of the world's edible fish. The diseases can affect the final production in intensive aquaculture; in seabass, aquaculture vibriosis is one of the most important diseases producing huge economical losses in this industry. The usual methodology to solve the problems associated with the bacterial pathology has been the use of antibiotics, with known environmental consequences. This is why probiotic bacteria are proposed as an alternative fight against pathogenic bacteria. The aim of this study was to analyse a strain of Bacillus velezensis D-18 isolated from a wastewater sample collected from a fish farm, for use as probiotics in aquaculture. The strain was evaluated in vitro through various mechanisms of selection, obtaining as results for growth inhibition by co-culture a reduction of 30%; B. velezensis D-18 was able to survive at 1.5-h exposure to 10% seabass bile, and at pH 4, its survival is 5% and reducing by 60% the adhesion capacity of V. anguillarum 507 to the mucus of seabass and in vivo by performing a challenge. Therefore, in conclusion, we consider B. velezensis D-18 isolate from wastewater samples collected from the farms as a good candidate probiotic in the prevention of the infection by Vibrio anguillarum 507 in European seabass after in vitro and biosafety assays.
Antioxidant activities and selected characteristics of gelatin hydrolysates from seabass skin as affected by production processes were investigated. Hydrolysates were prepared using different processes, including hydrolysis during and... more
Antioxidant activities and selected characteristics of gelatin hydrolysates from seabass skin as affected by production processes were investigated. Hydrolysates were prepared using different processes, including hydrolysis during and after gelatin extraction. Samples hydrolysed during gela-tin extraction showed a higher degree of hydrolysis (DH) and yield compared with those hydrolysed after gelatin extraction (p<0.05). All hydrolysates had a creamy yellowish colour. A lower abundance of volatile compounds was found in the hydrolysates produced during gelatin extraction, in comparison with those obtained after gelatin extraction. Hydrolysates prepared during gelatin extraction had higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidative power (FRAP) and ferrous ion chelating activity (p<0.05). Following a simulated in vitro gastrointes-tinal digestion, the DPPH radical scavenging activity and FRAP of the hydrolysates was retained, whilst ferrous ion chelating activity increased. The most appropriate conditions for the generation of antioxidant hydrolysates from seabass skin were identified.
Gelatins from seabass skin without and with defatting, extracted in the absence and presence of tannic acid at various concentrations (0e0.4 g/kg), were characterised. Gelatins from skin without defatting had higher gel strength (p <... more
Gelatins from seabass skin without and with defatting, extracted in the absence and presence of tannic acid at various concentrations (0e0.4 g/kg), were characterised. Gelatins from skin without defatting had higher gel strength (p < 0.05) with coincidentally higher band intensity of a-and b-chains, compared with those extracted from defatted skin. Gelatins from defatted skin had lower fishy odour with concomitantly lower thiobarbituric acid reactive substances and peroxide value. Lower abundance of volatile compounds, including aldehydes, ketones and alcohols was found in gelatin extracted from defatted skin. The addition of tannic acid during gelatin extraction could lower lipid oxidation, fishy odour as well as the formation of volatile compounds, especially hexanal and heptanal, in the resulting gelatins, regardless of defatting. Therefore, gelatin with reduced fishy odour could be prepared from seabass skin, in which 0.2 g/kg tannic acid was incorporated during extraction.
This study investigated the antioxidant, immunomodulatory and antiproliferative potentials of gelatin hydrolysates from seabass skins in cell model systems. Gelatin hydrolysates were extracted from seabass skins using different processes... more
This study investigated the antioxidant, immunomodulatory and antiproliferative potentials of gelatin hydrolysates from seabass skins in cell model systems. Gelatin hydrolysates were extracted from seabass skins using different processes and enzyme concentrations. The ability of the hydrolysates to protect against H 2 O 2-induced DNA damage was assessed on U937 cells using the Comet assay, and one of the samples showed DNA protective effects. All samples showed immunomodulatory potential by significantly (P < 0.05) reducing interleukin-6 (IL-6) and IL-1b production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Antiproliferative activities of seabass skin hydrolysates were measured using human colon cancer (Caco-2) and liver cancer (HepG2) cell lines as the model cell cultures. The inhibition of cell proliferation of Caco-2 and HepG2 cancer cells occurred in a dose-dependent manner at concentrations of 1–25 mg mL À1. Therefore, seabass skin hydrolysates prepared using an appropriate process could serve as a potential functional food ingredient with various health benefits.
Vibrio species are the most common and serious pathogens in fish and shellfish marine aquaculture worldwide. The present study aimed to determine the prevalence of Vibrio spp. in seabass and seabream in fish markets, especially... more
Vibrio species are the most common and serious pathogens in fish and shellfish marine aquaculture worldwide. The present study aimed to determine the prevalence of Vibrio spp. in seabass and seabream in fish markets, especially streptomycin-resistant strains that have great public health importance. A total of 30 seabass (Dicentrarchus Labrax) and 30 seabream (Sparus aurata) were purchased from fish markets at Kafr El Sheikh Governorate and subjected to bacteriological examination. The PCR assay was used for the detection of virulence genes (tdh and trh), aminoglycoside resistance gene (aadA1), and toxR gene. The results indicated that the total prevalence of Vibrio spp. was 26.66%, including V. parahaemolyticus (8.3%), V. alginolyticus (8.3%), V. mimicus (3.3%), V. harveyi (5%) and V. vulnificus (1.6%). The toxR, trh, and aadA1 genes were found in all V. parahaemolyticus isolates while tdh gene was found in 80% of isolates. Antimicrobial sensitivity test of V. parahaemolyticus isolates showed sensitivity to ciprofloxacin, norfloxacin, cefotaxime, and chloramphenicol. Vibrio parahaemolyticus isolates were resistant to ampicillin, erythromycin, streptomycin, and gentamycin. The present results indicated that good hygienic measures should be taken to avoid infection with Vibrio species, especially V. parahaemolyticus that can pose a great risk to human health.
Studying gamete biology can provide important information about a species fertilization strategy as well as their reproductive ecology. Currently, there is a lack of knowledge about how long sea bass Dicentrarchus labrax eggs can remain... more
Studying gamete biology can provide important information about a species fertilization strategy as well as their reproductive ecology. Currently, there is a lack of knowledge about how long sea bass Dicentrarchus labrax eggs can remain viable after being activated in seawater. The objectives of this study were to understand the effects of pre-incubation of fresh and overripe sea bass eggs in seawater and to determine the duration of egg receptivity. Pooled eggs (fresh and overripe) from 4 females were pre-incubated in seawater for 0 min (control), 0.5 min, 1 min, 3 min, 10 min and 30 min and then fertilized by pooled sperm from 4 males. The fresh eggs had a higher fertilization success than overripe eggs. Our results revealed a significant effect of pre-incubation time for both the fresh (P < 0.01) and overripe eggs (P < 0.01). Fertilization success of eggs significantly declined for both these treatments after 3 min of pre-incubation, which clearly indicates that sea bass eggs are able to be fertilized by sperm for up to 3 min after release into seawater. This study has particular importance for understanding fertilization strategies, reproductive potential, as well as reproductive ecology of sea bass.
Cage farming of marine finfish is an alternative to meet increasing demand for food fish. Culture of Asian seabass in open sea floating net cages made of either HDPE or GI pipes, has been successfully demonstrated off Karwar, south India.... more
Cage farming of marine finfish is an alternative to meet increasing demand for food fish. Culture of Asian seabass in open sea floating net cages made of either HDPE or GI pipes, has been successfully demonstrated off Karwar, south India. Fish were fed with chopped oilsardine. Various growth parameters like average daily growth rate (ADGR), survival rate (SR), specific growth rate (SGR) and biomass index (BI) were estimated. Mean weight and length at the end of the 150 days experimental period was 1.02 kg and 412.05 mm respectively with a SR of 68.8%. The economics of cage farming was also worked out. The need to standardise stocking densities and feeding rate has been emphasised.
DAX1 (NR0B1), a member of the nuclear receptors super family, has been shown to be involved in the genetic sex determination and in gonadal differentiation in several vertebrate species. In the aquaculture fish European sea bass,... more
DAX1 (NR0B1), a member of the nuclear receptors super family, has been shown to be involved in the genetic sex determination and in gonadal differentiation in several vertebrate species. In the aquaculture fish European sea bass, Dicentrarchus labrax, and in the generality of fish species, the mechanisms of sex determination and differentiation have not been elucidated. The present study aimed at characterizing the European DAX1 gene and its developmental expression at the mRNA level.
