On August 25, 2025, Gu et al. from Ocean University of China published their latest research results in Marine Drugs, entitled "New Strategy for the Degradation of High-Concentration Sodium Alginate with Recombinant Enzyme 102C300C-Vgb and the Beneficial Effects of Its Degradation Products on the Gut Health of Stichopus japonicus". They have pioneered a novel biotechnological route to accelerate the marine glycobiology supply chain. The paper focuses on optimizing the enzymatic hydrolysis of high-concentration sodium alginate (SA) using the high-activity recombinant alginate lyase, 102C300C-Vgb. The core breakthrough is the efficient, pilot-scale production of low-molecular-weight alginate oligosaccharides (AOS) and the subsequent validation of their profound beneficial effects as a functional feed additive, significantly enhancing the gut health and growth performance of the aquaculture organism Stichopus japonicus.

Research Background

The utilization of Marine Polysaccharides, particularly alginates sourced from brown algae, represents a cornerstone of functional marine biotechnology. AOS are recognized as high-value functional glycans due to their established roles in modulating immune response, improving fat metabolism, and enhancing gut bacterial community balance in aquaculture. While enzymatic hydrolysis is the preferred route for AOS production due to its specificity and environmental friendliness, existing methods are hampered by two major constraints: the high cost and impracticality of degrading concentrated alginate feedstocks, and the low activity and stability of many current alginate lyases, which fail to meet the robustness required for industrial application. This paper directly addresses the urgent need for a high-efficiency, scalable enzymatic strategy capable of generating high yields of specified, biologically active AOS for the burgeoning aquaculture industry.

Research Results

• Overcoming High-Viscosity Barriers to Maximize AOS Yield

A major technical obstacle in industrial-scale AOS production is the high viscosity of concentrated Alginate solutions, which severely restricts substrate concentration and subsequent enzyme-substrate interaction. The authors effectively addressed this by leveraging the specific high activity of the recombinant alginate lyase, 102C300C-Vgb. Through methodical optimization, they demonstrated that the enzyme could successfully hydrolyze a challenging 20% sodium alginate solution. The optimal enzyme dosage of 25 U/g achieved a remarkable enzymatic hydrolysis yield of 59.98%, significantly surpassing the efficiency of traditional enzymatic methods and directly tackling the high-cost challenge of industrial production.

• Structural Verification of Biologically Active Oligosaccharide Products

Following the pilot-scale enzymatic reaction, the degradation product (PSDP) was subject to meticulous Structural and Compositional Analysis to confirm the production of the desired low-molecular-weight glycans. Fourier-transform infrared spectroscopy (FTIR) confirmed the successful depolymerization. Crucially, electrospray ionization mass spectrometry (ESI-MS) and molecular weight (Mw) distribution analysis verified that the PSDP primarily comprised low-degree-of-polymerization alginate oligosaccharides. This confirmation is vital, as the Biological Activity of these marine glycans—including their anti-inflammatory, antioxidant, and prebiotic effects—is strongly correlated with their low molecular weight.

Fig.1 The Mw distribution (1) and ESI-MS (2) of the degradation product (A) and PSDP (B). (Gu, et al., 2025)

• PSDP Enhances Growth and Remodels Sea Cucumber Gut Morphology

The most compelling aspect of the study is the biological validation in the commercially valuable sea cucumber, Stichopus japonicus. When fed a PSDP-supplemented diet, the sea cucumbers exhibited statistically significant enhancements in growth performance, evidenced by increased average wet and dry weights of the body wall compared to control groups. Furthermore, histological analysis of the intestinal tissue revealed positive morphological changes: the PSDP diet led to a measurable increase in intestinal fold width. This observation suggests that the AOS enhances the absorptive surface area and strengthens the gut barrier integrity, supporting improved nutrient assimilation and overall health.

Fig.2 Intestinal tissue sections of S. japonicus fed diets with different PSDP levels. (Gu, et al., 2025)

Conclusion

This research provides a significant leap forward in the scalable production of bioactive marine glycans. The successful deployment of the high-performance recombinant enzyme 102C300C-Vgb for the degradation of 20% SA establishes a new benchmark for industrial efficiency, drastically improving the economic viability of AOS synthesis. Furthermore, the demonstrated in vivo efficacy of the resulting PSDP—evidenced by enhanced growth, optimized fat/protein proportion, and strengthened intestinal morphology in S. japonicus—validates its innovative application as a superior functional ingredient. This work not only optimizes a complex biochemical process but also provides a powerful, sustainable, and proven solution for improving health and productivity in high-value marine aquaculture.