Tinghong Ming

Butyrate, a short-chain fatty acid (SCFA), is increasingly recognized as a functional feed additive in aquaculture. However, its effects on crustacean health and performance remain unclear. This meta-analysis synthesizes findings from 23 studies (2011–2025) examining butyrate supplementation across four crustacean groups: shrimp, crabs, crayfish, and prawns. Effect sizes were calculated for growth performance (final body weight, specific growth rate, survival rate), feed efficiency (feed conversion ratio, protein efficiency ratio), and digestive enzyme activities (amylase, lipase, alkaline phosphatase, total protease) in freshwater and marine environments. Results indicate that butyrate supplementation generally enhanced the digestive enzyme activity in both freshwater and marine environments, although the magnitude of the effect varied among enzyme types and habitats, with freshwater species showing improvements in alkaline phosphatase, amylase, lipase, and total protease, and marine species showing improvements in amylase, lipase, and total protease. Feed efficiency improved in freshwater (protein efficiency ratio) and marine species (feed conversion ratio). Growth-related outcomes, including final body weight and survival rate, were generally improved across both environments. Dose–response analyses indicated that dietary inclusion levels of 1–2% were associated with the most consistent improvements in digestive enzyme activity and growth performance. These findings support the potential use of butyrate as a functional feed strategy to improve productivity and sustainability in crustacean aquaculture. These effects may be mediated by multiple mechanisms, including improved intestinal epithelial integrity, the modulation of gut microbiota, and the regulation of immune and metabolic processes.

The bioconversion of waste carbon into medium-chain carboxylic acids has become feasible, and their subsequent utilization for hydrocarbon production via the Kolbe reaction as a bioenergy source represents a highly promising route.

Aeromonas hydrophila-induced enteritis presents a significant challenge to the intensive aquaculture of black sea bream (Acanthopagrus schlegelii). Studies have shown that probiotic supplementation provides a promising alternative to conventional antibiotic applications for disease prevention in aquaculture. In this study, we investigated the protective effects of dietary supplementation with Bacillus velezensis NDB on the growth, immunity, and intestinal microbiota of black sea bream against A. hydrophila-induced intestinal damage. A total of one hundred and eight black sea bream fingerlings (initial body weight of 9.44 ± 0.03 g) were randomly assigned to three groups (total of nine tanks, twelve fish per tank): a control group (CON, normal diet), an infected group (AH, normal diet for 28 days followed by A. hydrophila infection at 1.0 × 10⁷ CFU/mL), and a probiotic-treated group (AH+NDB, diet supplemented with 1.43 × 10⁸ CFU/g B. velezensis NDB for 28 days, followed by A. hydrophila infection at 1.0 × 10⁷ CFU/mL). The results showed that the weight gain rate in the AH+NDB group was 139.44 ± 48.61%, which was significantly higher than that in the CN (126.81 ± 43.48%) and AH (132.48 ± 63.54%) groups. The pathological symptoms of black sea bream induced by A. hydrophila, including gill and abdominal hemorrhage, villus deformation, and inflammatory infiltration, were alleviated in the AH+NDB group. Histological and biochemical analyses showed the dietary supplementation of B. velezensis NDB enhanced antioxidant enzyme activities (SOD and CAT) and reduced lipid peroxidation (MDA) in the AH+NDB group. Compared to the AH group, the AH+NDB group exhibited significantly upregulated expression levels of anti-inflammatory markers (il10 and tgf-β), and significantly downregulated levels of pro-inflammatory cytokines (il1, tnf-α, and ifng). Moreover, dietary supplementation with B. velezensis NDB increased the abundance of beneficial genera (e.g., Bacillus and Ruegeria), and decreased the abundance of opportunistic pathogenic genera (e.g., Aeromonas and Vibrio), thus enhancing the carbohydrate/amino acid biosynthesis and promoting the nucleoside and nucleotide biosynthesis to alleviate A. hydrophila-induced enteritis. Collectively, the study demonstrated that dietary supplementation with B. velezensis NDB can effectively promote growth performance and enhances immune function in black sea bream, thereby providing significant benefits for fish culture.

Microbial proteins offer a sustainable alternative for animal nutrition. Rossellomorea marisflavi NDS, a bacterium isolated from seawater, was previously identified as a promising candidate due to its high protein content. This study aimed to enhance its single cell protein production through systemic fermentation optimization. Single-factor optimization in shake flask determined the optimal conditions to be: a salinity of 20‰ NaCl, a temperature of 32 °C, and an initial pH of 7.3, and a medium composed of 1% (w/v) corn flour, 1% peptone, 0.3% beef extract, and 0.2% KCl. Scaling up to a 10 L bioreactor demonstrated that a two-stage agitation strategy (150 rpm for the first 20 h followed by 180 rpm for the remaining 12 h) enhanced single cell protein yield. Furthermore, allowing the pH to fluctuate freely was more beneficial for protein production than maintaining a constant pH of 7.3 ± 0.02. Under these optimized conditions, the biomass composition (wet weight) was determined to be 2.3767 ± 0.0205% crude ash, 15.6013 ± 0.0082% crude protein, 0.1023 ± 0.0026% crude lipid, and 2.6997 ± 0.0021% carbohydrates. Amino acid analysis revealed a rich profile, with lysine and glutamic acid being the predominant essential and non-essential amino acids, respectively. Fatty acids analysis indicated that C14:1n5 was the most dominant. These findings underscore the potential of R. marisflavi NDS as a high-quality dietary protein supplement and provide a solid foundation for its industrial-scale production.

Spirulina (Arthrospira platensis) is globally recognized for its high nutritional value and potential as a sustainable food source. However, the influence of targeted nutrient supplementation on its biochemical composition and microbial safety under tropical open-pond conditions remains underexplored, particularly in sub-Saharan Africa. This study evaluated the effects of three nutrient supplementation regimes (compositions A, B, and C) and a control on Spirulina cultivated over 30 days in raceway ponds at the Nomayos Spirulina Production Farm in Cameroon. All treatments maintained physicochemical parameters within ranges favorable for Spirulina growth. Composition A significantly enhanced protein content (60.38 ± 0.68%), while composition C promoted carbohydrate accumulation (28.02 ± 0.41%). Microbial assessments revealed variable contamination levels, with composition B exhibiting the highest Escherichia coli (1.05 ± 0.075 × 10⁵ CFU/g) and Salmonella/Shigella (4.09 ± 1.81 × 10⁵ CFU/g) counts, potentially due to nutrient-induced changes or post-harvest handling factors. Correlation analyses revealed a moderate positive relationship between nitrogen input and protein synthesis (r = 0.309), which was not statistically significant (p = 0.329). Additionally, higher pH was significantly correlated with total mesophilic counts (r = 0.661, p = 0.019) and E. coli (r = 0.655, p = 0.020). These findings highlight the importance of nutrient formulation and environmental management in improving nutritional quality while minimizing microbial risks during Spirulina cultivation in tropical, low-tech settings.

Autolysis in the sea cucumber Apostichopus japonicus is typically triggered by degradation caused by microorganisms within their bodies. However, information on this topic remains limited. Recently, we isolated and purified a bacterial strain from hydrolyzed instant sea cucumber samples. To investigate its potential role in the autolysis process, this study employed whole-genome sequencing and metabolomics to explore its genetic and metabolic characteristics. The identified strain was classified as Lysinibacillus xylanilyticus and designated with the number XL-2024. Its genome size is 5,075,210 bp with a GC content of 37.33%, encoding 5275 genes. Functional database comparisons revealed that the protein-coding genes were distributed among glucose metabolism hydrolase, metal hydrolase, lysozyme, cell wall hydrolase, and CAZymes. Compared to 20 closely related strains, L. xylanilyticus XL-2024 shared 1502 core homologous genes and had 707 specific genes. These specific genes were mainly involved in the carbohydrate metabolism pathway and exhibited glycosyl bond hydrolase activity. Metabolomic analysis showed that L. xlanilyticus XL-2024 produced several metabolites related to polysaccharide degradation, including peptidase, glucanase, and pectinase. Additionally, the presence of antibacterial metabolites such as propionic acid and ginkgo acid among its metabolites may enhance the stability of the sea cucumber hydrolysate. In summary, L. xylanilyticus XL-2024 may play a pivotal role in the autolysis of A. japonicus. The results of this study provide a strong foundation for understanding how to prevent autolysis in A. japonicus and for better utilizing L. xylanilyticus XL-2024.

Reports regarding the composition and functions of microorganisms in activated sludge from wastewater treatment plants for treating tuna processing wastewater remains scarce, with prevailing studies focusing on municipal and industrial wastewater. This study delves into the efficiency and biological dynamics of activated sludge from tuna processing wastewater, particularly under conditions of high lipid content, for pollutant removal. Through metagenomic analysis, we dissected the structure of microbial community, and its relevant biological functions as well as pathways of nitrogen and lipid metabolism in activated sludge. The findings revealed the presence of 19 phyla, 1,880 genera, and 7,974 species, with Proteobacteria emerging as the predominant phylum. The study assessed the relative abundance of the core microorganisms involved in nitrogen removal, including Thauera sp. MZ1T and Alicycliphilus denitrificans K601, among others. Moreover, the results also suggested that a diverse array of fatty acid-degrading microbes, such as Thauera aminoaromatica and Cupriavidus necator H16, could thrive under lipid-rich conditions. This research can provide some referable information for insights into optimizing the operations of wastewater treatment and identify some potential microbial agents for nitrogen and fatty acid degradation.

Ferritin with a highly symmetrical cage-like structure is not only key in the reversible storage of iron in efficient ferroxidase activity; it also provides unique coordination environments for the conjugation of heavy metal ions other than those associated with iron. However, research regarding the effect of these bound heavy metal ions on ferritin is scarce. In the present study, we prepared a marine invertebrate ferritin from Dendrorhynchus zhejiangensis (DzFer) and found that it could withstand extreme pH fluctuation. We then demonstrated its capacity to interact with Ag⁺ or Cu²⁺ ions using various biochemical and spectroscopic methods and X-ray crystallography. Structural and biochemical analyses revealed that both Ag⁺ and Cu²⁺ were able to bind to the DzFer cage via metal-coordination bonds and that their binding sites were mainly located inside the three-fold channel of DzFer. Furthermore, Ag⁺ was shown to have a higher selectivity for sulfur-containing amino acid residues and appeared to bind preferentially at the ferroxidase site of DzFer as compared with Cu²⁺. Thus, it is far more likely to inhibit the ferroxidase activity of DzFer. The results provide new insights into the effect of heavy metal ions on the iron-binding capacity of a marine invertebrate ferritin.

Ferritin is widely acknowledged as a conservative iron storage protein found in almost all living kingdoms. Apostichopus japonicus (Selenka) is among the oldest echinoderm fauna and has unique regenerative potential, but the catalytic mechanism of iron oxidation in A. japonicus ferritin (AjFER) remains elusive. We previously identified several potential metal-binding sites at the ferroxidase center, the three- and four-fold channels in AjFER. Herein, we prepared AjFER, AjFER-E25A/E60A/E105A, AjFER-D129A/E132A, and AjFER-E168A mutants, investigated their structures, and functionally characterized these ferritins with respect to Fe²⁺ uptake using X-ray techniques together with biochemical analytical methods. A crystallographic model of the AjFER-D129A/E132A mutant, which was solved to a resolution of 1.98 Å, suggested that the substitutions had a significant influence on the quaternary structure of the three-fold channel compared to that of AjFER. The structures of these ferritins in solution were determined based on the molecular envelopes of AjFER and its variants by small-angle X-ray scattering, and the structures were almost consistent with the characteristics of well-folded and globular-shaped proteins. Comparative biochemical analyses indicated that site-directed mutagenesis of metal-binding sites in AjFER presented relatively low rates of iron oxidation and thermostability, as well as weak iron-binding affinity, suggesting that these potential metal-binding sites play critical roles in the catalytic activity of ferritin. These findings provide profound insight into the structure–function relationships related to marine invertebrate ferritins.