ABSTRACT
Zinc is an essential element for metabolism of Nile tilapia (Oreochromis niloticus). Nanomaterials have important benefits in aquaculture. The present study evaluated the effects of green-synthesized zinc oxide nanoparticles (ZnO-NPs) using Ulva fasciata extract as an anti-fungal agent against Candida albicans (C. albicans) in vitro and in vivo in O. niloticus. A total of 252 apparent healthy O. niloticus (20 ± 0.457 g/fish) were randomly allocated into six groups: The 1st group fed on basal diet contaminated with C. albicans 15 × l06 CFU/g diet, the 2nd group fed basal diet only, the 3rd and 5th groups fed the basal diet supplemented with 40 or 60 mg/kg ZnO-NPs, respectively, and the 4th and 6th groups fed the basal diet contaminated with C. albicans 15 × l06 CFU/g and concomitantly supplemented with 40 or 60 mg/kg ZnO-NPs, respectively. The experiment lasted for 8 weeks. The phyco-synthesized ZnO-NPs were characterized by XRD, UV-V, FTIR, TEM, and zeta potential. The anti-fungal activities of ZnO-NPs and the morphological changes to C. albicans cell due to ZnO-NPs were detected. The results revealed that dietary supplementation with the green-synthesized ZnO-NPs significantly improved the growth performance, survival, serum lysozyme activity, phagocytic activity, phagocytic index, respiratory burst activity, expression of immune-related genes (IL-1ß, TGF, TNF-α), digestive enzyme activity, and histopathological finding in C. albicans-infected group, with a relative superiority to 40 mg/kg feed ZnO-NPs. It could be concluded that supplementing diets with 40 mg/kg of phyco-synthesized ZnO-NPs could be considered a better choice for controlling candidiasis in Nile tilapia.
