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A feeding trial was conducted to evaluate response of European seabass (ESB, Dicentrarchus labrax) fry to graded levels of the dietary organic salt, sodium butyrate (SB). ESB with 0.45 g were fed four experimental diets contained: 0, 0.1, 0.2 and 0.3% SB and assigned as: control (CTRL), SB1, SB2 and SB3 respectively for 12-weeks. Results showed a significant (P≤0.05) elevation of all measured growth criteria induced by SB2 and SB3 diets intake relative to CTRL diet (SB-free). Both 0.2% and 0.3% dietary SB supplementation had led to appreciable increase in protein concomitant with decrease in lipid contents of fish, as well as enhancement of fish hematological profile. All measured immunological parameters in fish serum have remarkably increased: immunoglobulin (+198%), respiratory burst activity (+78.2%), phagocytosis (+42.3%), myeloperoxidase (+42.2%), lysozyme (+10.6%) and bactericidal (42.8%) activities with the oral-ingestion of SB, particularly at 0.2% then 0.3% level in comparison to CTRL. Besides, SB can maintain a healthy balance of bacterial load in the gut through boosting beneficial bacteria and inhibiting pathogens within the distal intestine, thereby modulate and stimulate immunity response of fish. Records of intestinal sections-measurement emphasized the positive effects of SB2 diet on the intestinal lumen causing activation in the development of muscle layers-thickness, goblet cells count and villi length and width of fish. These results evidenced the advantageous effect of SB on gut-health functionality, leading to higher capacity of disease resistance and growth rate for ESB fry. In conclusion, our findings indicate that inclusion of 2g micro-encapsulated SB/Kg diet could provide a safer potent alternative to antibiotic use, to benefit health status, reinforce immunity response, modulate the distal-intestine microbiota and increase cell-proliferation in the intestinal crypts of ESB fry. Table1: Formulation and proximate analyses of the experimental diets (% DM) as fed to European seabass (Dicentrarchus labrax) fry. Ingredients Diets (g/Kg) CTRL SB1 SB2 SB3 Fish Meal (70% CP) 1 600 600 600 600 Soybean meal (solvent extracted, 42% CP) 2 165 165 165 165

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Screening of fungal isolates collected from different locations of Alexandria coast, Egypt, was carried out to obtain new biologically active metabolites against some virulent fish pathogens (Edwardsiella tarda, Aeromonas hydrophila, Vibrio ordalli and Vibrio angularuim). Among 26 fungal isolates, Aspergillus terreus var. africanus was identified as the most potent isolate. Production of the bioactive material was optimized using response surface methodology including fermentation media, incubation period, temperature, pH, and thermo-stability. Spectral properties of the gas chromatography/mass spectrum of the ethyl acetate crude extract were determined. Partially purified components of the crude extract were chromatographically separated and bioassayed. Out of ten separated compounds, five were with considerable antibacterial agent. The bio-toxicity of crude showed a slight toxicity against the brine shrimp Artemia salina (LC50 = 1,500 μg/l). Antibacterial activity of the crude was compared with some known standard antibiotics and found to be superior over many where its MIC against some pathogen reached 1 μg/ml.

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Objective: Marine fungi play an important role in human and animal health, leading compounds to new drug discoveries and prospects for their bioactivity potential. Materials and Methods: Paecilomyces WE3-F was isolated from marine sediment (Red Sea, Shalateen, Egypt). Fungal isolate was screened for their antagonistic activity against four Gram-positive (Bacillus cereus, Lesteria monocytogenes, Micrococcus luteus and Staphylococcu aureus) and four Gram-negative (Aeromonas hydrophila, Flavobacteruim sp, Pseudomonas aeruginosa and Vibrio cholera,) pathogenic bacteria. Paecilomyces WE3-F was identified using 18S rRNA technology. Seven factors were chosen to be screened for bioactivity using the Placket Burman experimental design: sucrose, yeast extract, Na NO3, temperature, initial pH, inoculum size, and incubation period. Results: Among conditional factors, acidic pH and 1.5 ml inoculum size favored the bioactive metabolites. Furthermore, a number of solvents have been experimented for the extraction of the bioactive metabolite(s). Dichloromethane (DCM) crude extract from the fermentation broth of a marine Paecilomyces WE3-F showed the highest activity with averages of 26 and 24 mm against G-ve and G+ve, respectively. Under optimal culture conditions, the maximum extractable compound concentration in a 10-L culture medium reached 83.4 mg/L. Based on data obtained by thin layer chromatogram (TLC), gas chromatography -mass spectrum (GC-MS) and Fourier Transform Infrared (FTIR) the major compound, betulin was structurally identified. Conclusions:The isolated marine Paecilomyces WE3-F, therefore, showed the ability to produce a betulin yield after optimal operating conditions for antibacterial potential.