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Mar Drugs
2025 Aug 25;239:. doi: 10.3390/md23090339.
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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.
Gu Z, Niu F, Yang P, Gong W, Mukhtar H, Li S, Zheng Y, Zhong Y, Cui H, Li J, Mou H, Li D.
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High viscosity of alginate means a relatively low substrate concentration, which limits the efficiency of hydrolysis, resulting in one of the main challenges for the large-scale production of alginate oligosaccharides (AOS). In this study, a pilot-scale degradation product (PSDP) of the recombinant enzyme 102C300C-Vgb was produced for the first time at a substrate concentration of up to 20% sodium alginate. The optimal conditions for SA digestion were: enzyme dosage of 25 U/g, enzymatic temperature of 45 °C, enzymatic pH of 7.0, and enzymatic time of 24 h. Under these conditions, the yield of enzymatic hydrolysis was consistently in the range of 69% to 70%. The average molecular weight (Mw) of PSDP was 1496.36 Da, mainly containing oligosaccharides with degrees of polymerization ranging from 2 to 4. The low-Mw PSDP was subsequently applied in the diet of sea cucumber Stichopus japonicus. The results showed that the body wall weight of S. japonicus increased significantly after 40 days of feeding with a 0.09% PSDP-supplemented diet. Furthermore, PSDP-supplemented diet significantly increased the thickness of the serosal and submucosal layers and the width folds of mucosa of the sea cucumber gut. The abundance of pathogenic bacteria was reduced effectively, and that of beneficial bacteria increased significantly after being fed with PSDP. The results demonstrated that PSDP can serve as a digestive health enhancer for sea cucumbers, promoting their healthy growth.
2023KJ040 Youth Innovation Team Program of Universities in Shandong Province, 2022TZXD005 Shandong Province Key R & D Program, YZ2024002 Shandong Province Marine Aquaculture Innovation and Entrepreneurship Community Project, 42106110 National Natural Science Foundation of China, 32202064 National Natural Science Foundation of China, 20224BAB215044 Natural Science Foundation of Jiangxi Province, 2021M701547 China Postdoctoral Science Foundation
Figure 1. The yield and proportion of reducing sugar of digested products under different conditions. (A) Enzyme dosage; (B) Temperature; (C) pH; (D) Time. Different letters displayed above the bars on the column chart denote significant differences among treatments (n = 3) (mean ± SE).
Figure 2. FTIR analyses of SA and its degradation product.
Figure 3. The Mw distribution (1) and ESI-MS (2) of the degradation product (A) and PSDP (B).
Figure 4. The changes of average wet weight (A) and average dry weight in body wall (B) of S. japonicus in different feeding groups. Different letters (uppercase letters: 20 days of cultivation; lowercase letters: 40 days of cultivation) displayed above the bars on the column chart denote significant differences among treatments (n = 10) (mean ± SE).
Figure 5. The changes of the protein (A)/fat (B) content (1) and proportion (2) in body wall of S. japonicus in different feeding groups. The protein/fat proportion of the body wall was calculated by dividing the protein/fat content of the individual by the dry weight of the body wall. Different letters (uppercase letters: 20 days of cultivation; lowercase letters: 40 days of cultivation) displayed above the bars on the column chart denote significant differences among treatments (n = 10) (mean ± SE).
Figure 6. Intestinal tissue sections of S. japonicus fed diets with different PSDP levels. SE: Serosal layer; MU: Muscularis propria; SU: Submucosa; FO: Fold width.
Figure 7. Analysis of differences in abundance between PSDP6 and the CT at the genus level: (A). compared to CT, the bacteriuml communities of increased abundance in PSDP6; (B). compared to CT, the bacteriuml communities of decreased abundance in PSDP6. Values with * were p < 0.05 between two treatments (n = 4) (mean ± SE).
Figure 8. Analysis of differences in abundance between PSDP9 and the CT at the genus level: (A). compared to CT, the bacteriuml communities of increased abundance in PSDP9; (B). compared to CT, the bacteriuml communities of decreased abundance in PSDP9. Values with * were p < 0.05 between two treatments (n = 4) (mean ± SE).
Figure 9. Flow chart of pilot production equipment.
