Comprehensive Characterization of Sargassum thunbergii Extracts Using Subcritical Water for Biopolymer Application
- Alternative Title
- 바이오폴리머 응용을 위한 아임계 수 이용 지충이(Sargassum thunbergii)추출물의 포괄적 특성 연구
- Abstract
- This study explores the utilization of the marine brown seaweed, Sargassum thunbergii, to develop eco-friendly and multifunctional biopolymer applications, aiming to establish sustainable strategies for marine biomass valorization. Specifically, subcritical water extract (SWE) was employed to extract various bioactive compounds from S. thunbergii, which were then evaluated for their potential in biorefinery processes and biopolymer film development. The first study analyzed the physicochemical and biofunctional properties of S. thunbergii extracts prepared using SWE and conventional solvent extraction. The SWE demonstrated superior properties, with maximum phlorotannin content (13.57 ± 0.19 mg PGE/g), total sugar content (61.95 ± 0.75 mg glucose/g), and antioxidant activity (ABTS⁺, DPPH, FRAP assays: 17.99 ± 0.02, 56.72 ± 0.09, and 29.79 ± 0.11 mg TE/g, respectively) observed at 180℃. Antimicrobial tests revealed the strongest inhibitory effects against Escherichia coli and Bacillus cereus. These results highlight SWE as a green and effective process for extracting bioactive compounds from S. thunbergii, surpassing the performance of traditional solvent extraction methods. The second study optimized the subcritical water extraction conditions of S. thunbergii to establish a sustainable biorefinery process and comprehensively evaluated the bioactive and structural properties of the optimized extract (OSE). Using response surface methodology, the optimal conditions (195.43℃, 18.82 min, solid-to-liquid ratio of 0.032 g/mL) yielded maximum total phenolic content (29.01 ± 0.28 mg PGE/g). The OSE exhibited potent antioxidants, antidiabetic (α-glucosidase inhibition, IC50 1.87 ± 0.09 mg/mL), antihypertensive (ACE inhibition, IC50 0.24 ± 0.01 mg/mL), antimicrobial, anti- inflammatory, and anti-aging properties. Structural analyses (NMR, FT-IR, XRD, and FE-SEM) also demonstrated the potential for repurposing residual biomass as biofuel. These findings validate SWE as an eco-friendly, zero-waste strategy for the comprehensive utilization of S. thunbergii. The third study developed functional biopolymer-based packaging materials by incorporating OSE into chitosan/polyvinyl alcohol-gelatin (CS/PVA-GE) composite films. By varying OSE concentrations (0%-5%), significant improvements were observed in the films' mechanical (tensile strength: 20.91 ± 2.03 MPa at 5% OSE), physicochemical (contact angle: 94.9°), and moisture resistance properties. Packaging trials with strawberries revealed that the films effectively maintained fruit quality for up to 7 days, supported by the antioxidative and antimicrobial properties of OSE’s phenolic and flavonoid compounds. These findings demonstrate that OSE-based biopolymer films can effectively support the storage stability and quality retention of food products as functional packaging materials. This research demonstrates the potential of S. thunbergii for multifunctional applications in biopolymer development, highlighting its utilization in food, pharmaceutical, and cosmetic industries. Furthermore, the SWE-based biorefinery process contributes to zero-waste strategies and sustainable development goals, offering an eco-friendly solution for marine biomass valorization while addressing global challenges in environmental preservation.
- Issued Date
- 2025
- Awarded Date
- 2025-02
- Type
- Dissertation
- Publisher
- 국립부경대학교 대학원
- Affiliation
- 국립부경대학교 대학원
- Department
- 대학원 식품공학과
- Advisor
- Byung-Soo Chun
- Table Of Contents
- Chapter 1 1
General Introduction 1
1.1. Biopolymer film 1
1.2. Sargassum thunbergii 5
1.3. Subcritical water extraction 10
References 16
Chapter 2 25
Physicochemical and biofunctional properties of Sargassum thunbergii extracts obtained from subcritical water extraction and conventional solvent extraction 25
Abstract 25
2.1. Introduction 27
2.2. Materials and methods 29
2.2.1. Materials and chemicals 29
2.2.2. Proximate composition analysis 30
2.2.3. Subcritical water and methanol extraction 31
2.2.4. Physical properties 34
2.2.4.1. pH 34
2.2.4.2. Color 34
2.2.5. Antioxidant activity 34
2.2.5.1. DPPH, ABTS+ and FRAP assay 34
2.2.5.2. Total phenolic contents 35
2.2.6. Total sugar content 36
2.2.7. Reducing sugar content 36
2.2.8. HPLC analysis of phenolic compounds 37
2.2.8.1. Preparation of samples 37
2.2.8.2. HPLC method 37
2.2.9. Antimicrobial activity 40
2.2.10. Statistical analysis 40
2.3. Results and discussion 41
2.3.1. Proximate composition 41
2.3.2. Extraction efficiency 43
2.3.3. Color and pH 43
2.3.4. Antioxidant activity 47
2.3.4.1. Total phenolic contents 47
2.3.4.2. Antioxidant activity 47
2.3.4.3. Correlation between TPC and radical scavenging 48
2.3.5. Total sugar contents and reducing sugar contents 49
2.3.6. Recovery of phenolic compounds 52
2.3.7. Antimicrobial activities 56
2.4. Conclusion 60
References 61
Chapter 3 67
Optimization of eco-friendly biorefinery process from Sargassum thunbergii: characterization of phenolic and bioactive compounds 67
Abstract 67
3.1. Introduction 69
3.2. Materials and methods 73
3.2.1. Materials and chemicals 73
3.2.2. Subcritical water extraction 73
3.2.3. RSM and data analysis 74
3.2.4. Pysicochemical properties 77
3.2.4.1. Color and maillard reaction products 77
3.2.4.2. Monosaccharide analysis 77
3.2.4.3. Sulfate content 78
3.2.4.4. Molecular weight analysis 79
3.2.4.5. Total phenolic contents and total flavonoids contents 79
3.2.4.6. Total sugar contents and reducins sugar contents 80
3.2.4.7. GC-MS 80
3.2.4.8. UPLC-ESI-QTOF-MS/MS analysis 81
3.2.4.9. NMR spectroscopy 83
3.2.5. Biological activities· 83
3.2.5.1. Antioxidant activity 83
3.2.5.2. Antihypertensive activity 84
3.2.5.3. α-Glucosidase inhibitory activity 85
3.2.5.4. Antimicrobial activity 86
3.2.5.5. Cytotoxicity and anti-inflammatory activities 87
3.2.5.6. Skin care activities 89
3.2.6. Analysis of the RAW, OSE, and OSE-R properties 93
3.2.6.1. FT-IR 93
3.2.6.2. XRD 94
3.2.6.3. Elemental analysis 94
3.2.6.4. TGA 95
3.2.6.5. FE-SEM 95
3.2.7. Statistical analysis 95
3.3. Results and discussion 96
3.3.1. Single-factor analysis 96
3.3.1.1. Effect of temperature on TPC 96
3.3.1.2. Effect of reaction time on TPC 96
3.3.1.3. Effect of S/L on TPC 97
3.3.2. Optimization of extraction parameters 99
3.3.2.1. Statistical analysis and model fitting 99
3.3.2.2. Model validation and optimization 100
3.3.3. Pysicochemical properties 104
3.3.3.1. Color and MRPs 104
3.3.3.2. Monosaccharide composition 108
3.3.3.3. Sulfate content 110
3.3.3.4. Molecular weight analysis 111
3.3.3.5. Total phenolic contents and total flavonoids contents 114
3.3.3.6. Total sugar contents and reducing sugar contents 115
3.3.3.7. Identification of chemical compounds by GC–MS 118
3.3.3.8. Phenolic compound profiling by UPLC–ESI–QTOF-MS/MS 126
3.3.3.9. Structural analysis by NMR 141
3.3.4. Biological activities 143
3.3.4.1. Antioxidant activity 143
3.3.4.2. Antihypertensive activity 144
3.3.4.3. α-Glucosidase inhibitory activity. 146
3.3.4.4. Antimicrobial activity 149
3.3.4.5. Cytotoxicity and anti-inflammatory activities 152
3.3.4.6. In vitro skin care activities 155
3.3.5. Residual biomass analysis 160
3.3.5.1. Elemental analysis 160
3.3.5.2. FT-IR 162
3.3.5.3. XRD 163
3.3.5.4. TGA 164
3.3.5.5. FE-SEM 167
3.4. Conclusion 169
References 171
Chapter 4 193
Development of a functional biopolymer film for food packaging incorporating optimized Sargassum thunbergii extract using subcritical water extract 193
Abstract 193
4.1. Introduction 195
4.2. Materials and methods 198
4.2.1. Materials and sample preparation 198
4.2.2. Subcritical water extraction 198
4.2.3. Preparation of the film 199
4.2.4. Pysicochemical properties 199
4.2.4.1. Color 199
4.2.4.2. Thickness 200
4.2.4.3. Mechanical properties of the films 200
4.2.5. Water-related properties 202
4.2.5.1. Water solubility 202
4.2.5.2. Swelling properties 202
4.2.5.3. Water vapor permeability 203
4.2.5.4. Contact angle 204
4.2.6. Surface analysis 204
4.2.6.1. FE-SEM 204
4.2.6.2. AFM 205
4.2.7. Structural analysis 205
4.2.7.1. FT-IR 205
4.2.7.2. XRD 206
4.2.8. Biological activities 206
4.2.8.1. Antioxidative activity evaludation 206
4.2.8.2. Assessment of food quality retention 207
4.2.9. Statistical analysis
4.3. Results and discussion 208
4.3.1. Physical and mechanical properties 208
4.3.1.1. Color and appearance 208
4.3.1.2. Tensile strength and elongation at break 212
4.3.2. Water-related properties 214
4.3.3. Surface analysis 218
4.3.3.1. FE-SEM 218
4.3.3.2. AFM 220
4.3.4. Structural analysis 222
4.3.4.1. FT-IR 222
4.3.4.2. XRD 225
4.3.5. Biological activities 228
4.3.5.1. Antioxidative activities 228
4.3.5.2. Assessment of food quality retention 231
4.4. Conclusion 234
References 236
Summary 242
Abstract (In Korean) 244
- Degree
- Doctor
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