West Anhui University

Quorum sensing is a central mechanism by which signal bacteria sense and integrate signaling molecules to coordinate gene expression and physiological activities at the community level. To investigate how exogenous signal molecules regulate the maintenance of algal-bacterial symbiosis, this study constructed a dialysis membrane-coupled algal-bacterial photobioreactor and separately amended it with N-butyryl-l-homoserine lactone (C4-HSL), N-hexanoyl-l-homoserine lactone (C6-HSL), and N-(3-oxodecanoyl)-l-homoserine lactone (3-oxo-C10-HSL), systematically investigated their effects on nutrient removal, microbial community composition, and functional characteristics within the system. Compared with the control, all three N-acyl-homoserine lactones (AHLs) enhanced total nitrogen and total phosphorus removal and stimulated biomass (sludge) growth, while redirecting microalgal carbon allocation toward lipid accumulation; notably, the C6-HSL treatment achieved the highest nitrogen (80.39 %) and phosphorus (53.01 %) removal efficiencies. Metagenomic analyses revealed that exogenous AHLs exerted selective effects on the microbial assemblage, enriching dominant signal-responsive bacteria whose relative abundance was positively correlated with nitrogen and phosphorus removal performance. Furthermore, genes associated with nitrogen metabolism, the tricarboxylic acid cycle, and glycolysis were more abundant in the 3-oxo-C10-HSL and C6-HSL groups, indicating that strengthened metabolic coupling likely underpins the observed biomass increase and enhanced nutrient removal. Collectively, these findings demonstrate that AHL-mediated signaling is a key driver shaping algal-bacterial interactions, community assembly, and functional expression.

Porcine epidermal growth factor (PoEGF) promotes intestinal epithelial development and enhances immune function in weaned piglets, offering potential as an alternative to in-feed antibiotics. However, large-scale application of recombinant PoEGF (rPoEGF) is hindered by high production costs and complex purification requirements. In this study, we constructed a recombinant Saccharomyces cerevisiae INVSc1 strain capable of expressing and secreting rPoEGF through the integration of an α-factor signal peptide-PoEGF-6 × His expression cassette. Expression was confirmed by SDS-PAGE and Western blot analysis, and bioactivity was validated using a BALB/c 3T3 fibroblast proliferation assay, yielding a maximum mitogenic activity of 10,963 U/mL. To improve production efficiency, a two-stage fermentation strategy was developed and optimized in a 4-L bioreactor. The process consisted of a glucose-based fed-batch growth phase followed by galactose-induced expression under optimized conditions (25 °C, pH 5.0, DO 30 %). This approach enabled high-cell-density cultivation (OD₆₀₀ ≈ 71.5) and achieved a final secreted protein yield of 30.2 mg/L. Notably, the culture containing active rPoEGF could be directly applied as a functional feed additive without the need for downstream purification. These results provide a practical, scalable, and cost-effective approach for producing bioactive rPoEGF and support its future application in swine production as a safe, antibiotic-free growth promoter.

This study explored the regulatory effects of sweet potato pericarp polyphenols on protein oxidation in commercially available fresh milk. Fresh milk samples from brands such as Yili, Mengniu, and Bright Dairy were collected and supplemented with sweet potato pericarp polyphenols. The samples were then stored at 4°C, and analyses were conducted to evaluate the antioxidant indices, protein oxidation products, microbial count, and texture parameters. The free radical scavenging capacities measured by 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt assays, as well as the decline in the total antioxidant capacity, were significantly lower in the treatment group compared with the control group. In addition, the treatment group showed lower carbonyl content, reduced oxidative loss of free sulfhydryl groups, inhibited excessive formation of disulfide bonds, a slower increase in thiobarbituric acid reactive substances values, suppressed protein hydrolysis, improved microbial safety, and enhanced textural stability. Therefore, sweet potato pericarp polyphenol can effectively inhibit protein oxidation in fresh milk, preserve protein structural stability, and enhance antioxidant and textural quality. These findings provide a theoretical basis for their potential application in fresh milk preservatives.