Chlorella ellipsoidea is a freshwater green microalga that has great prospect for the sustainable development of aquaculture industry. Microalgae require optimal lighting conditions for efficient photosynthesis. The key to cost-effective algal biomass production is to optimize algae growth conditions. This study aimed to investigate the effects of various wavelengths viz. white (380–750 nm), green (510 nm), blue (475 nm), and red (650 nm) light-emitting diodes (LEDs) on the growth, pigment content (chlorophyll-a, chlorophyll-b, and β-carotene), and proximate composition of C. ellipsoidea with a photoperiod of 12 h:12 h light: dark cycle under indoor environmental conditions. C. ellipsoidea was cultured in Bold's Basal Medium for 18 days. The cell density (125.36×10⁵ cells ml⁻¹), cell dry weight (58.9 ± 4.57 mg L⁻¹), optical density (1.66 ± 0.08 g L⁻¹), chlorophyll-a (7.31 ± 0.04 μg ml⁻¹), chlorophyll-b (2.73 ± 0.13 μg ml⁻¹), and β-carotene (0.39 ± 0.04 μg ml⁻¹) content of C. ellipsoidea were significantly (P < 0.05) higher at 15^th-day when cultured under blue LED light exposure. Significantly lower growth and nutritional values were obtained under red LED light exposure compared to the control and other LEDs spectra. In Pearson correlation analysis, the cell density and cell dry weight values showed a strong positive correlation with the values of pigment contents of C. ellipsoidea in all the treatments. The LEDs light spectra showed significant effects on proximate composition of C. ellipsoidea. Protein and lipid contents of C. ellipsoidea were significantly higher in blue LED growth conditions compared to white, green, and red LEDs. C. ellipsoidea cells were 3˗7.04 μm in size and the maximum area of the cell was 38.94 μm² in blue LED treatment. Results of this study demonstrated that blue LED light spectra was the most suitable condition to induce nutritionally rich biomass production of C. ellipsoidea, which can be used as a potential source of fish feed towards sustainable aquaculture.

This study aimed to isolate and identify probiotic bacteria from the gut ofBarbonymus gonionotusand evaluate their effects on growth, hematological parameters, and breeding performances of the host. Five probiotic bacteria viz. Enterococcus xiangfangensis(GFB-1),Pseudomonas stutzeri(GFB-2),Bacillus subtilis(GFB-3),Citrobacter freundii(GFB-4), andP. aeruginosa(GFB-5) were isolated and identified using16S rRNAgene sequencing. Application of a consortium of probiotic strains (1–3 × 1.35 × 10⁹ CFU kg⁻¹) or individual strain such as GFB-1 (1.62 × 10⁹ CFU kg⁻¹), GFB-2 (1.43 × 10⁹ CFU kg⁻¹), GFB-3 (1.06 × 10⁹ CFU kg⁻¹), GFB-4 (1.5 × 10⁹ CFU kg⁻¹) or GFB-5 (1.43 × 10⁹ CFU kg⁻¹feed) through feed significantly improved growth, histological and hematological parameters and reproductive performances ofB. gonionotuscompared to untreated control. Moreover, the application of these probiotics significantly increased gut lactic acid bacteria and activities of digestive enzymes but did not show any antibiotic resistance nor any cytotoxicity in vitro. The highest beneficial effects on treated fishes were recorded by the application of GFB-1, GFB-2, GFB-3, and a consortium of these bacteria (T2). This is the first report of the improvement of growth and health ofB. gonionotusfishes by its gut bacteria.

The purpose of this study was to investigate the presence of pathogenic bacteria, specifically Escherichia coli and Salmonella and Vibrio species, and their antimicrobial resistance in shrimp aquaculture facilities of Bagerhat (Bangladesh). Sediment samples were collected from both Penaeus monodon and Macrobrachium rosenbergii farms and shrimp samples from the Macrobrachium rosenbergii facility. The abovementioned bacteria were not found, but five Enterobacterales (Proteus penneri, Proteus alimentorum, Morganella morganii, Enterobacter hormaechei subsp. xiangfangensis and Plesiomonas shigelloides) were detected. This is the first documented case of Enterobacter hormaechei subsp. xiangfangensis in a shrimp farm. Nine antibiotics—ampicillin, gentamicin, chloramphenicol, oxytetracycline, nitrofurantoin, levofloxacin, ciprofloxacin, azithromycin, and co-trimoxazole—were selected for antibiotic resistance testing, and the majority (88.9%) had at least one isolate that was resistant. Across sources, 78.0% of isolates were resistant to at least one antimicrobial, and multidrug resistance was also detected in 29.3% of all isolates. Despite the low number of samples analyzed, nine in total, the results of this experiment emphasize that shrimp farms in Bagerhat may have a problem with antimicrobial-resistant bacteria. This could have negative impacts on shrimp quality and consumers’ health.

In this study, we determined the effects of dietary chitosan on the growth, biochemical composition, gut microbiota, and hematological and histological parameters of juvenile Barbonymus gonionotus. Three test diets containing three different concentrations (1, 2, and 3 g kg-1 feed) of dietary chitosan were formulated. A basal diet without dietary chitosan was considered a control, and the fish were reared for 60 days. Comparing the effects of the dietary chitosan-containing diets with those of the control diet, we found that dietary chitosan significantly improved the muscle growth, nutrient and mineral contents, hematological parameters, lactic acid bacterium abundance, and digestive enzyme activities of B. gonionotus. Moreover, dietary chitosan significantly inhibited the growth of pathogenic bacteria in fish. Interestingly, an increase in the dietary chitosan level significantly enhanced the protein contents of the muscles and inversely significantly decreased the lipid contents compared to those with the basal diet. Quantitative study revealed that dietary chitosan significantly enhanced the length of intestinal villi, and qualitative study showed that dietary chitosan considerably reduced the fat content in the liver and improved the morphology of the kidney compared to those with the basal diet. Taken together, our results suggest that the application of dietary chitosan at a dose of 1 g kg-1 feed produced the highest benefit to treated B. gonionotus, indicating its potential for safe use in aquaculture.