The nutrition and flavor of shrimp paste came from hydrolyzation by enzymes that were produced by microorganisms. The salt‐tolerant strain Virgibacillus halodenitrificans ST‐1 isolated from shrimp paste was studied and used in the fermentation of shrimp paste. The strain and the protease produced by ST‐1 were investigated. The optimum pH of the protease was 8.0, and the reaction temperature was 30°C. The protease showed high activity in the range of pH (5.0–11.0) and NaCl concentration (1%–15%). Divalent cations such as Ba²⁺, Ca²⁺, Mg²⁺, Mn²⁺, and Si²⁺ could enhance the protease activity. Residual activity of protease was more than 90% when it was incubated with PMSF and H₂O₂. Also, the enzyme retained more than 90% of initial activity after it was incubated with organic solvents. Variety of natural proteins could be substrates of the protease. By analyzing the release rate of free amino acids, it was predicted that the cleavage sites of the protease were mainly Glu, Asp, Gly, Leu, and Lys. Moreover, the hydrolysates of the protease had antioxidant activity, especially for DPPH and superoxide anion radical scavenging. The strain ST‐1 and the protease both were excellent candidates for food industries.

Being a biologically diversed hotspot in the global marine ecosystem, the Beibu Gulf is inhabited by a high diversity of fish and serves as a vital fishing ground in China. Due to continuous overfishing, the fishery resource has drastically declined in the Beibu Gulf. However, information about the ichthyoplankton assemblages in this area is still lacking. In this present study, ichthyoplankton diversity, spatial and temporal distribution patterns, and assemblage structures were examined using the specimens collected in the late summer–autumn and winter of 2022 in the Beibu Gulf, and the relationship between ichthyoplankton assemblage and environmental variables was studied. A total of 117 ichthyoplankton taxa, belonging to 13 orders and 42 families, were recorded. The most abundant families were Gerreidae, Leiognathidae, and Sillaginidae in late summer–autumn, accounting for 38.74%, 27.95%, and 9.94%, respectively. Sparidae, Platycephalidae, and Sillaginidae were the most abundant families in winter, accounting for 34.03%, 17.15%, and 8.20%, respectively. Cluster analysis identified five assemblages in late summer-autumn and four assemblages in winter. The most characteristic species in each cluster were Terapon jarbua, Sillago sihama, Leiognathus brevirostris, Mene maculate, and Scomberoides tol in late summer-autumn and Scomberomorus commerson, Acanthopagrus latus, Sillago sp., and Evynnis cardinalis in winter. The results of the canonical correspondence analysis indicated that pH, chlorophyll-a (Chl-a), depth, dissolved oxygen (DO), sea surface salinity (SSS), total nitrogen (TN), and total phosphorus (TP) were the major environmental variables affecting the ichthyoplankton assemblage structure in the Beibu Gulf. The finding of this study will provide valuable information in conserving fish spawning grounds and developing fishery management practices to protect fishery resources in the Beibu Gulf.

Macroalgae-derived polyphenols have been considered as a potential source of food supplements that can enhance the nutritional value and extend the shelf life of foods. However, thermal treatment during food processing as well as storage might induce the degradation of some bioactive compounds in the extract. In the present study, the stability of the extract from the edible brown algae Ascophyllum nodosum was evaluated under thermal treatment (40–90 °C). Significant differences in TPC, RSC, and antioxidant activity were found during all treatments. The total phenol content (TPC) and antioxidant activity (DPPH scavenging activity) decreased up to 5% and 10%, respectively, after 6 h of thermal treatment, while the reducing sugar content (RSC) increased from 8 to 35% as the temperature increased from 40 to 90 °C. The stability of the extract during storage with or without exposure to air was evaluated at room temperature (25 °C) and low temperature (4 °C) for 108 h, and the influence of the solvent used to contain the extract has been investigated by studying both concentrated and non-concentrated extracts. It was found that the extract stored at 4 °C without exposure to air had a negligible TPC change, while RSC increased in the extract exposed to air, suggesting that oxygen in the air might accelerate polysaccharide degradation during storage. Antioxidant activity of extracts remained constant at both 4 and 25 °C, regardless of exposure to air.