Low-molecular-mass chondroitin sulfate (CS) have attracted wide attention due to their better bioavailability and biological activity than highmolecular-mass CS. To obtain low-molecular-mass sulfate chondropolysaccharides with higher anti-colorectal cancer activity, sturgeon chondroitin sulfate (SCS) from the hybrid sturgeon Acipenser schrenckii × Huso dauricus was enzymatically depolymerized. Response surface methodology was used to optimize the enzymatic process based on inhibitory activity against the proliferation of HT-29 cells. The optimal enzymatic conditions were determined as 0.103 IU/mg, 1.005 mg/mL and 87 min for enzyme dosage, substrate concentration, and enzymatic digestion time, respectively. Furthermore, SCS-F2 with low molecular mass and high anticancer activity was prepared by ultrafiltration. In order to explore its safety for consumption, the acute toxicity of SCS-F2 was evaluated by using an animal model. The experimental results showed that SCS-F2 has no adverse effects on body mass, food intake, blood biochemical indexes or visceral tissues while reducing the number of aberrant colonic crypts, indicating that SCS-F2 has inhibitory and preventive effects on colorectal cancer and meets the safety requirements of food and health products. Therefore, SCS-F2 is safe and non-toxic, and has anti-colorectal cancer activity.

In order to determine its taxonomic status and to improve its enzyme production level, the chondroitinase-producing strain PL-410 was identified based on morphology and 16S rRNA gene sequence analysis, and the fermentation conditions for chondroitinase production by this strain were optimized by single factor experiments, Plackett-Burman design, the steepest ascent method and Box-Behnken design combined with response surface methodology. The results showed that the strain PL-410 was identified as Pseudarthrobacter sp. The optimal medium was composed of chondroitin sulfate from bovine cartilage 7.5 g/L, tryptone 2.5 g/L, NaCl 5 g/L, KH₂PO₄ 0.3 g/L, and initial pH 6.53. The optimal fermentation conditions were as follows: inoculum volume 2.98%, medium volume in shaking flasks 8%, shaker rotation speed 160 r/min, fermentation temperature 24 ℃, and fermentation time 27.63 h. The chondroitinase activity under these conditions was 2531.765 U/L, which was 29.7 times higher than that before optimization (85.229 U/L).

Curing fish roes with high concentrations of sodium chloride is needed to ensure the taste and storage quality of caviar during its production. To solve the problem of the use of high concentrations of sodium salt during the processing of Oncorhynchus masou caviar, one-factor-at-a-time method, Plackett-Burman (PB) design, steepest ascent design and response surface methodology were used to optimize the formulation of low-sodium salt substitutes based on total bacterial count. The results showed that potassium lactate, potassium chloride and magnesium chloride substitution at 17.64%, 14.61% and 34.36%, respectively had the smallest negative effect on caviar quality and could improve the pH value, water activity and color difference of caviar and inhibit microbial growth in it. Therefore, the use of the low-sodium salt formulation for the preparation of caviar can improve the product quality and safety, indicating its great application potential.

This study aimed to investigate the effect of using an optimized complex sodium salt substitute formulation, comprising potassium lactate (17.64%), potassium chloride (14.61%), magnesium chloride (34.36%), and sodium chloride (33.39%), on the quality of Oncorhynchus masou caviar at different storage temperatures and to compare it with the traditional sodium chloride curing method. Caviar samples were stored at 20, 27, and 34 °C, respectively, and the effect of the new formulation on the quality characteristics of the caviar was systematically evaluated through the determination of microbiological indicators, pH, water activity, total volatile basic nitrogen content and other physicochemical indicators. In addition, the shelf life of the samples at 0 and 4 °C was predicted using the accelerated shelf life test model. The results showed that using sodium salt substitute formulation could effectively inhibit microbial growth, slow down the spoilage process of the product, and significantly extend the shelf-life of caviar, which is a significant advantage over the traditional sodium chloride curing method. This study provides theoretical support and practical guidance for the improvement of caviar processing technology and salt reduction in the food industry.