미역 줄기 젖산 발효물의 생리활성 특성 및 알긴산 기반 기능성 하이드로겔의 활성물질 방출 특성 = Functional Characterization of Fermented Seaweed By-products and Controlled Release Behavior of Alginate Hydrogels Encapsulating Bioactive Components

다국어 초록 (Multilingual Abstract)

This study proposes an integrated biorefinery approach for valorizing Undaria pinnatifida stem by-products through lactic acid fermentation, alginate recovery and modification, and the fabrication of pH-responsive hydrogels for controlled phlorotannin release. Three lactic acid bacteria strains—Weissella cibaria, Lactiplantibacillus plantarum, and Streptococcus salivarius—were individually applied, and an additional mixed-culture treatment (LM), composed of these three strains, was evaluated separately. All strains induced substantial acidification within 24 h, with LP and the mixed-culture LM producing the most pronounced pH reduction. Fermentation markedly altered the distribution of pigments and phenolic constituents, shifting chlorophylls, carotenoids, and phloro tannins from bound fractions in the residue toward soluble fractions in the supernatant. The supernatant phlorotannin content increased in all fermented groups, most notably in LM and SS, indicating enhanced enzymatic deconjugation and improved extractability. Alginate recovered from fermented residues exhibited increased extraction yields and significant molecular weight reduction compared with the non-fermented control. Gel permeation chromatography confirmed thatLM generated the lowest molecular weight alginate, demonstrating the strongest depolymerization capability among treatments. These molecular alterations directly influenced hydrogel performance: hydrogels formulated with higher-molecular-weight alginate formed stronger and more cohesive networks, whereas hydrogels containing increased proportions of low-molecular-weight fermented alginate displayed weakened gel integrity and reduced structural stability. Phlorotannin-loaded hydrogels showed distinct pH-responsive release behavior during simulated digestion. In simulated gastric fluid (SGF, pH 1.2), release remained limited (~30–35%) and stabilized without further progression, consistent with acid-induced contraction of alginate matrices. In simulated intestinal fluid (SIF, pH 6.8), rapid matrix swelling facilitated nearly complete release (>95%) within 120 min. This pronounced shift in release kinetics demonstrates the efficacy of fermented alginate hydrogels as enteric delivery vehicles capable of protecting phenolic compounds under acidic conditions and promoting efficient intestinal release. Overall, lactic acid fermentation enhanced pigment and phenolic bioavailability, improved alginate recoverability, and enabled controlled molecular tailoring to produce functional hydrogels. The resulting pH-responsive phlorotannin delivery system underscores the potential of seaweed by-product fermentation as a scalable strategy for developing advanced marine biomaterials and functional food applications.

목차 (Table of Contents)

• I. 서론 5
• Ⅱ. 재료 및 방법 8
• 1. 시료 8
• 2. 미역 젖산 발효물 제조 9
• 3. Total chlorophylls 및 total Carotenoids 분석 10
• 4. Fucoxanthin 함량 분석 11
• 5. Total polyphenol 및 total flavonoid 분석 12
• 6. Total phlorotannin 분석 13
• 7. 항산화능 (DPPH 및 ABTS radical scavenging activities) 분석 14
• 8. 알긴산 추출 및 알긴산 함량 분석 15
• 9. 알긴산 분자량 분석(Gel permeation chromatography, GPC) 16
• 10. 알긴산 기반 기능성 하이드로겔 제조 17
• 11. 미역 알긴산 하이드로겔의 in vitro 기능성 방출 특성 (simulated gastric fluid(SGF) 및 simulated intestinal fluid(SIF)) 18
• 12. 통계 분석 19
• Ⅲ. 결과 및 고찰 20
• 1. 미역 줄기의 젖산 발효물의 pH 변화 20
• 2. 미역 줄기 젖산 발효물의 total chlorophylls 함량 변화 22
• 3. 미역 줄기 젖산 발효물의 total carotenoids 함량 변화 25
• 4. 미역 줄기 젖산 발효물의 fucoxanthin 함량 변화 27
• 5. 미역 줄기 젖산 발효물의 total polyphenol 함량 30
• 6. 미역 줄기 젖산 발효물의 total flavonoid 함량 33
• 7. 미역 줄기 젖산 발효물의 total phlorotannin 함량 35
• 8. 미역 줄기 젖산 발효물의 DPPH 라디칼 소거능 37
• 9. 미역 줄기 젖산 발효물의 ABTS 라디칼 소거능 39
• 10. 미역 줄기 젖산 발효물의 알긴산의 함량 41
• 11. 미역 줄기 젖산 발효물의 알긴산의 분자량 특성 44
• 12. 미역 줄기 알긴산 하이드로겔의 구조적 특성 47
• 13. 미역 알긴산 하이드로겔의 phlorotannin 방출 특성 (in vitro simulated gastric fluid(SGF) 및 simulated intestinal fluid(SIF)) 50
• 14. 미역 알긴산 하이드로겔의 in vitro 방출 특성 (in vitro simulated gastric fluid(SGF) 및 simulated intestinal fluid(SIF)) 54
• Ⅳ. 요약 57