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Effect of different carbon sources on nursery performance of Pacific white shrimp (Litopenaeus vannamei) cultivated in biofloc system was investigated. Shrimp postlarvae (98.47 AE 8.6 mg) were fed for 32 days in tanks with water volume of 130 L and density of 1 individual L À1 . One control treatment and four biofloc treatments (BFT1, BFT2, BFT3 and BFT4) with adding different carbon sources including molasses, starch, wheat flour and mixture of them, respectively, were considered at equal weight ratios. According to the results, salinity, dissolved oxygen and pH were not significantly different among the biofloc treatments (P > 0.05). Maximum pH (8.27) and maximum dissolved oxygen (6.35 mg L À1 ) were recorded in the control. Maximum (0.43 mg L À1 ) and minimum (0.09 mg L À1 ) ammonia were recorded in the control and BFT2, respectively (P < 0.05). Using simple carbohydrates (molasses and starch) lowered the ammonia concentration significantly. The highest increase in body weight (1640.43 AE 231.28 mg), growth rate, specific growth rate (8.97 AE 0.42% per day) and biomass (190.29 AE 26.83 mg) were found in BFT1 and the highest survival (90 AE 0.77%) was found in BFT4. The highest feed conversion (1.52 AE 0.23) and the lowest feed efficiency (66.81 AE 7.95) were observed in the control (P < 0.05). The proximate composition analysis revealed an increase in lipid and ash in biofloc treatments. Results indicated that using biofloc technology with zero-water exchange system and adding carbon sources could help to recycle waste and improve the water quality. Moreover, the type of carbonaceous organic matter as a substrate for heterotrophic bacteria would be effective in degradation and metabolization of ammonia and nitrite.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused COVID-19 disease in China. So far, no vaccine has licensed to protect against infection with COVID-19, therefore an effective COVID-19 vaccine needed. The aim of this study was to predict antigenic peptides of SARS-CoV-2 for designing the COVID-19 vaccine using immunoinformatic analysis. In this study, T and B-cell epitopes of S protein were predicted and screened based on the antigenicity, toxicity, allergenicity, and cross-reactivity with human proteomes. The epitopes were joined by the appropriate linker. LT-IIc as an adjuvant was attached to the end of the structure. The secondary and 3D structure of the vaccine was predicted. The refinement process was performed to improve the quality of the 3D model structure; the validation process is performed using the Ramachandran plot and ProSA z-score. The proposed vaccine's binding affinity to the HLA-A11:01 and HLA-DRB1_01:01 molecule was evaluated by molecular docking. Using molecular dynamics, the stability of vaccine-HLA complexes was also evaluated. Finally, in silico gene cloning was performed in the pET30a (+) vector. The findings suggest that the current vaccine may be a promising vaccine to prevent SARS-CoV-2 infection.

The present study assessed the effects of different types of feeds and salinity levels on water quality, growth performance, survival rate and body composition of the Pacific white shrimp, Litopenaeus vannamei, juveniles in a biofloc system. Shrimp juveniles (2.56 ± 0.33 g) were cultured for 35 days in 300 L fibreglass tanks (water volume of 180 L) with a density of 1 g/L in six treatments. Three sources of feed (100% formulated feed, mixture of 66.6% formulated diet and 33.3% wet biofloc, and 100% wet biofloc) and two levels of salinity (10 and 32 ppt) were considered in two control groups and four biofloc treatments. Water quality parameters in the biofloc treatments were significantly better than control groups (p < .05). The highest increase in growth performance and survival rate were obtained in salinity of 32 ppt and mixed feed sources. Analysing the proximate composition of body shrimp indicates an increase in lipid and ash levels in biofloc treatments, which was more evident in the salinity of 32 ppt. In addition, the proximate analysis of shrimp body showed significant differences between biofloc treatments and control groups (p < .05). The highest FCR was found in the treatment with salinity level of 10 ppt and fed only with floc. Overall, it was found that the artificial diet supplemented with biofloc at the salinity of 32 showed better performance in the juvenile stage of Pacific white shrimp.

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