There has been a surge of research in the aquaculture industry investigating probiotic, prebiotic, and synbiotic interventions on the physiological mechanisms of fish, specifically digestive enzymes, oxidative stress, and antioxidant defense. In fish, probiotics have been shown to improve nutrient utilization and growth performance by stimulating digestive enzymes. Meanwhile, probiotics, prebiotics and synbiotics have also been studied for their ability to modulate oxidative stress and antioxidant defense mechanisms in fish, highlighting their multifaceted health benefits. This review identified current trends, research gaps, and future considerations in this evolving field. Although promising findings have been made, a significant research gap exists in understanding the specific role of probiotics prebiotics, and synbiotics in modulating digestive enzymes, oxidative stress, and antioxidant defense systems in a variety of fish species. As this study investigate into the existing body of literature, it becomes evident that while certain aspects of these interactions have been elucidated, a nuanced and comprehensive understanding still needs to be discovered. The variations in experimental design, species-specific responses, and the lack of standardized methodologies contribute to the complexity of the field. Digestive physiology and antioxidant defense mechanisms vary among different fish species, so future research should focus on species-specific responses to probiotic, prebiotic, and synbiotic formulations. It will also be possible to establish robust correlations between dietary interventions and observed effects through a systematic experimental design and methodology approach. Accordingly, further research is needed to understand the interactions between probiotics, prebiotics, and synbiotics in fish and digestive enzymes, oxidative stress, and antioxidant defense. Identifying research gaps and adopting standardized methodologies can help develop tailored strategies to optimize aquaculture fish health and growth performance.

Background: Various parts of Anacardium occidentale plant possess curative qualities like antidiabetic, anti-inflammatory, antibacterial, antifungal, and antioxidant. Aqueous extract of this plant leaf was used in biosynthesizing zinc oxide (ZnO) nanoaggregates using two precursors of zinc salt (zinc acetate dihydrate [Zn(CH₃COO)₂∙2H₂O] and zinc chloride [ZnCl₂]). The synthesized ZnO samples were used in a comparative study to investigate the antibacterial activity against selected Gram-positive and Gram-negative microbes [Staphylococcus aureus, Exiguobacterium aquaticum (Gram +ve) and Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii (Gram −ve)]. The synthesized ZnO nanoaggregates from the two precursors were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive x-ray spectroscopy (EDX) techniques. Results: Micrographs of SEM and TEM confirmed nanoparticles agglomerated into aggregates. While spherical nanoaggregates were identified in samples prepared from Zn(CH₃COO)₂∙2H₂O, flake-like structures were identified in samples synthesized from ZnCl₂. Particle size determined by TEM was 107.03 ± 1.54 nm and 206.58 ± 1.86 nm for zinc acetate dihydrate and zinc chloride precursors respectively. ZnO nanoaggregate synthesized using zinc acetate as precursor gave higher antibacterial activity than its counterpart, zinc chloride with K. pneumonia recording the highest inhibition zone of 2.08 ± 0.03 mm (67.53%) whereas S. aureus recorded the least inhibition zone of 1.06 ± 0.14 mm (34.75%) for ZnO nanoaggregate from zinc chloride precursor. Also, antibacterial activity increases with increasing concentration of the extract in general. However, A. baumannii, E. aquaticum, and K. pneumoniae did not follow the continuity trend with regards to the 250 ppm and 500 ppm concentrations. Conclusion: Biosynthesis of ZnO nanoaggregates using aqueous extract of A. occidentale leaf from zinc acetate dihydrate and zinc chloride as precursors was successful with the formation of nanospheres and nanoflakes. The study suggested that A. occidentale sp. could be an alternative source for the production of ZnO nanoparticles and are efficient antibacterial compounds against both Gram +ve and Gram −ve microbes with its promising effect against infectious bacteria.

The growing microbial resistance against antibiotics and the development of resistant strains has shifted the interests of many scientists to focus on metallic nanoparticle applications. Although several metal oxide nanoparticles have been synthesized using green route approach to measure their antimicrobial activity, there has been little or no literature on the use of Eucalyptus robusta Smith aqueous leaf extract mediated zinc oxide nanoparticles (ZnONPs). The study therefore examined the effect of two morphological nanostructures of Eucalyptus robusta Sm mediated ZnONPs and their antimicrobial and antifungal potential on some selected pathogens using disc diffusion method. The samples were characterized using Scanning and Transmission Electron Microscopy, Energy-Dispersive Spectroscopy and Fourier Transform Infrared Spectroscopy. From the results, the two ZnO samples were agglomerated with zinc oxide nanocrystalline structure sample calcined at 400 °C (ZnO NS₄₀₀) been spherical in shape while zinc oxide nanocrystalline structure sample calcined at 60 °C (ZnO NS₆₀) was rod-like. The sample calcined at higher temperature recorded the smallest particle size of 49.16 ± 1.6 nm as compared to the low temperature calcined sample of 51.04 ± 17.5 nm. It is obvious from the results that, ZnO NS₄₀₀ exhibited better antibacterial and antifungal activity than ZnO NS₆₀. Out of the different bacterial and fungal strains, ZnO NS₄₀₀ sample showed an enhanced activity against S. aureus (17.2 ± 0.1 mm) bacterial strain and C. albicans (15.7 ± 0.1 mm) fungal strain at 50 mg/ml. Since this sample showed higher antimicrobial and antifungal activity, it may be explored for its applications in some fields including medicine, agriculture, and aquaculture industry in combating some of the pathogens that has been a worry to the sector. Notwithstanding, the study also provides valuable insights for future studies aiming to explore the antimicrobial potential of other plant extracts mediated zinc oxide nanostructures.

This study sought to evaluate the added advantage of mediating ZnO nanostructures with a medicinal plant. The synthesized ZnO nanocrystalline structures were confirmed by Fourier transform infrared spectrometer and characterized through scanning electron microscope, transmission electron microscope, ultraviolet–visible spectroscopy, and energy‐dispersive X‐ray spectrometer. The antioxidant, anti‐inflammatory, and antimicrobial activities of the ZnO nanostructure mediated with methanol extracts of the leaf, fruit, and seed of Chrysophyllum albidum were then evaluated using DPPH assay, egg albumin denaturation assay, and agar well diffusion methods, respectively. All the characterization analyses revealed high‐purity hexagonal‐shaped ZnO nanoparticles which were agglomerated. The mean diameter of the particles determined were 11.3 ± 1.7 nm, 20.4 ± 3.2 nm, and 27.3 ± 6.6 nm for C. albidum seed, fruit, and leaf extract‐mediated ZnO NPs, respectively. The EC₅₀ values recorded for the antioxidant activity of the extract‐mediated ZnO NPs were 0.507 ± 0.015, 0.255 ± 0.006, 0.193 ± 0.003, and 0.004 ± 0.000 mg/mL for leaf, fruit, seed, and ascorbic acid, respectively. From the antimicrobial analysis, C. albidum seed extract‐mediated ZnO NPs recorded the highest zone of inhibition (24.33 ± 0.47) against S. aureus whereas C. albidum leaf extract‐mediated ZnO NPs gave the lowest zone of inhibition (13.00 ± 1.41) against E. coli at a concentration of 50 mg/mL. Moreover, C. albidum fruit extract‐mediated ZnO NPs presented the highest zone of inhibition (18.00 ± 0.82) against the fungus (C. albicans) also at a concentration of 50 mg/mL. The IC₅₀ values recorded for the anti‐inflammatory activity of the extract‐mediated ZnO NPs showed inhibition in the order fruit > seed > leaf. Meanwhile, extracts of the samples showed the presence of flavonoids, alkaloids, saponins, and glycosides as phytochemical constituents in the leaf, fruit, and seed samples. In conclusion, the synthesized ZnO NPs from the extracts of C. albidum displayed significant antioxidant, anti‐inflammatory, and antimicrobial activities against some selected microbes and fungi.

This study evaluated the effects of hypoxia on the heart of juvenile four-finger threadfin (Eleutheronema tetradactylum) through physiological and transcriptome analysis. Juveniles with an average weight of 122.82 g and length of 24.60 cm were used. Hypoxia significantly increased serum myocardial enzyme activities, including creatine kinase (CK), creatine kinase-MB isoenzyme, lactate dehydrogenase (LDH), and α-hydroxybutyrate dehydrogenase (HDBH). These indicators initially rose and then declined, reflecting cardiac stress and suggesting their potential as early hypoxia biomarkers for real-time aquaculture monitoring. Histological analysis revealed structural damage in myocardial fibers under hypoxia, with increasing severity over time. This underscores the need to minimize oxygen fluctuations to prevent cardiac tissue degeneration. Transcriptome analysis identified upregulated genes involved in cell communication, immune responses, and intracellular signaling, offering potential targets for breeding hypoxia-tolerant species. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis highlighted key pathways such as mitogen-activated protein kinase (MAPK), hypoxia-inducible factor-1 (HIF-1), endocytosis, and phagosome formation. The MAPK pathway plays a critical role in cellular stress responses, including survival, proliferation, and apoptosis. Hypoxia-induced activation of MAPKs like ERK, JNK, and p38 regulates stress-responsive genes. HIF-1 signaling regulates oxygen homeostasis, with HIF-1α stabilizing hypoxia-responsive genes such as VEGFA, which promotes vascular remodeling and enhances oxygen delivery. These findings collectively offer practical applications for enhancing aquaculture management, such as monitoring biochemical markers, adopting hypoxia-tolerant breeding, and adjusting environmental conditions to mitigate stress, ensuring better productivity and sustainability. This research provides a foundation for further studies on the molecular mechanisms of hypoxia stress in aquaculture species.