In order to explore the effects of probiotics on the water quality, growth performance, nonspecific immunity, digestion, and intestinal flora of Macrobrachium rosenbergii in the biofloc culture system, three groups (six replicates in each group) were set up and divided into no bacteria (control group, Con), Bacillus subtilis (BS), and effective microorganisms (EM) in the current experiment. After dissolution of the water, the carbon source (glucose) was evenly sprayed in the aquaculture tank to construct a biofloc with a C/N of 15. A total of 1260 giant freshwater prawn (Macrobrachium rosenbergii) with an initial body weight of (2.09 ± 0.03) g were randomly assigned to 18 tanks (70 per tank). BS group and EM group significantly reduced total nitrogen concentration. Both BS and EM groups significantly increased final mean body weight, weight gain, and specific growth rate, but significantly decreased feed conversion rate of Macrobrachium rosenbergii. BS group significantly increased plasma superoxide dismutase, lysozyme, and acid phosphatase contents, but significantly decreased plasma malonaldehyde content. EM group significantly increased serum acid phosphatase content and intestinal trypsin activity but significantly decreased the Chao and ACE index of species richness. BS group and EM group significantly decreased the abundance of Chloroflexi and Verrucomicrobiota. BS group significantly increased the abundance of Bacillus. Overall, adding probiotics affected water quality, Macrobrachium rosenbergii performance, and microbial community. The results showed that Bacillus subtilis is a good biofloc probiotic additive.

This study evaluated the effects of dietary soybean lecithin (SBL) on the growth, haematological indices, immunities, antioxidant capabilities, and inflammatory and intestinal barrier functions because little information of dietary SBL could be obtained in juvenile largemouth bass (Micropterus salmoides). The fish were fed identical diets except for SBL added at 0, 2, 4 and 8%. It was found that 4 and 8% SBL significantly increased fish weight gain and daily growth rate (p < 0.05), while 4% SBL was optimal for enhancing RBC, HGB, PLT, MCV, MCH, WBC and MON in blood, and ALB and ALP in serum (p < 0.05). SBL (4%) also significantly elevated the antioxidant enzymes activities of T-SOD, CAT, GR, GPx, GST and T-AOC and GSH contents; increased mRNA transcription levels of Nrf2, Cu/Zn-SOD, CAT, GR, GST3 and GPx3; and decreased MDA contents. Keap1a and Keap1b levels were markedly down-regulated (p < 0.05). SBL (4%) significantly enhanced levels of the immune factors (ACP, LZM and C3) and the mRNA expression levels of innate immune-related genes (C3, C4, CFD, HEPC and MHC-I) compared with the control groups (0%) (p < 0.05). SBL (4%) significantly increased IgM and T-NOS in the intestine (p < 0.05) and significantly decreased levels of TNF-α, IL-8, IL-1β and IFN-γ and increased TGF-β1 at both transcription and protein levels in the liver and intestine (p < 0.05). The mRNA expression levels of MAPK13, MAPK14 and NF-κB P65 were significantly decreased in the intestine in the 4% SBL groups (p < 0.05). Histological sections also demonstrated that 4% SBL protected intestinal morphological structures compared with controls. This included increased intestinal villus height and muscular thickness (p < 0.05). Furthermore, the mRNA expression levels of the intestinal epithelial cell tight junction proteins (TJs) (ZO-1, claudin-3, claudin-4, claudin-5, claudin-23 and claudin-34) and mucin-5AC were significantly up-regulated in the 4% SBL groups compared with the controls (p < 0.05). In conclusion, these results suggested that 4% dietary SBL could not only improve growth, haematological indices, antioxidant capabilities, immune responses and intestinal functions, but also alleviate inflammatory responses, thereby providing reference information for the feed formulations in cultured largemouth bass.

Microalgae play an important role in the formation of biofloc. To demonstrate the feasibility of Chlorella pyrenoidosa in biofloc formation, an experiment was performed with a simple random design consisting of five inoculation levels (in triplicate) of C. pyrenoidosa (0, 1 × 10⁸, 1 × 10⁹, 5 × 10⁹, and 1 × 10¹⁰ cells·L⁻¹) in the biofloc system. All treatments kept a C:N ratio of approximately 15:1. This study observed the effects of different initial concentrations of C. pyrenoidosa on biofloc formation, water quality and bacterial community in biofloc systems. The results indicated that C. pyrenoidosa had the ability to enhance biofloc development, especially when the C. pyrenoidosa initial concentration reached 5~10 × 10⁹ cells·L⁻¹. Too high or too low a concentration of C. pyrenoidosa will adversely affect the formation of biofloc. The effect of C. pyrenoidosa addition on water quality (TAN, NO₂⁻-N, and NO₃⁻-N) was not significant in the final stage. The inoculation of C. pyrenoidosa decreased the species richness and diversity of the bacterial community but increased the domination of Proteobacteria and Bacteroidota in the biofloc system, especially the order of Rhizobiales. The addition of C. pyrenoidosa could maintain water quality by increasing the proportion of several denitrifying bacteria, including Flavobacterium, Chryseobacterium, Pseudomonas, Brevundimonas, Xanthobacter, etc. These above dominant denitrifying bacteria in the biofloc system could play a major role in reducing the concentration of NO₂⁻-N and NO₃⁻-N. So, we recommended the reasonable concentration is 5~10 × 10⁹ cells·L⁻¹ if C. pyrenoidosa is used to rapidly produce biofloc.

A series of Ag-loaded and oxygen vacancy (OV)-containing BiOBr_(OV)/BiOI_0.08 (Ag/BiOBr_(OV)/BiOI_0.08) photocatalysts with varying Ag loading levels were synthesized via the solvothermal–photocatalytic reduction method. As confirmed via optical, photoelectrochemical, and 4-chlorophenol photodegradation experiments, a low Ag loading level significantly enhanced the photogenerated charge carrier (PCC) transfer on the BiOBr_(OV)/BiOI_0.08 semiconductor surface and the performance of Ag/BiOBr_(OV)/BiOI_0.08 photocatalysts, which was attributable to the synergism between the effect of OVs and the localized surface plasmon resonance (LSPR) of Ag nanoparticles. Additionally, BiOBr_(OV)/BiOI heterojunctions facilitated efficient visible-light harvesting and PCC separation. As indicated by finite-difference time-domain (FDTD) simulations and density functional theory (DFT) calculations, the electric field intensity in the “hot spots” generated at the interface between the BiOBr_(OV)/BiOI_0.08 semiconductor and Ag nanoparticles increased by more than eight times, and the presence of OVs and Ag atomic clusters introduced impurity energy levels in the semiconductor bandgap, improving PCC separation and Ag/BiOBr_(OV)/BiOI_0.08 photocatalytic efficiency. However, an increase in silver loading renders the composite metallic, suggesting a reduction in its photocatalytic performance. This work provides new insights for designing highly active visible light catalysts and contributes to the development of more efficient plasmonic catalysts.