Comparison of the Effects of Hot Water, Hot Acid, Microwave, and Enzymatic Extraction Methods on the Yield and Structural Characteristics of Ulvan

Articles in Press

Document Type : scientific research article

Authors

1 Department of Seafood Processing, Faculty of Fisheries and Environment, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

2 fisheries, Gorgan University of Agricultural Sciences and natural Resources

3 Mazandaran Uni

4 Sari University of Agricultural. Sciences and Natural Resources Faculty of Animal Science and Fisheries

Abstract

Background and Objective: Green algae of the genus Ulva, particularly the species Ulva rigida, are rich sources of the sulfated polysaccharide ulvan, which has gained special attention in the food and pharmaceutical industries due to its unique bioactive and functional properties. However, the extraction of this compound from the complex matrix of the algal cell wall faces challenges in terms of yield and preservation of structural integrity. The aim of this study was to comprehensively compare four extraction methods (hot water, hot acid, microwave, and enzymatic) to determine the most efficient method and to evaluate the physicochemical and biological properties of the final product.
Materials and Methods: In this study, U. rigida algae were collected from the coasts of Chabahar, Iran. After pretreatment, extraction was performed using the aforementioned methods. Following purification by the Sevag method and dialysis, the extraction yield was calculated. Chemical composition (carbohydrate, protein, sulfate and ash), techno-functional properties (water and oil holding capacity, emulsifying and foaming properties) and biological activities (DPPH radical scavenging, total antioxidant capacity, and antibacterial activity against Escherichia coli and Staphylococcus aureus) were analyzed using standard methods and SPSS 26 software.
Results: The results showed that the enzymatic method, with a yield of 28.40%, was significantly the most efficient extraction method, while the hot water method had the lowest yield (16.67%). Ulvan obtained by the enzymatic method contained 61.73% carbohydrate, 17.90% sulfate, and only 1.94% protein. The water and oil holding capacities of ulvan were recorded as 3.14 g/g and 2.67 g/g, respectively, which were lower than those of commercial alginate. Emulsifying and foaming properties improved with increasing concentration up to 4%. Furthermore, the maximum DPPH radical scavenging activity was observed at a concentration of 8 mg/mL (77.75%). In addition, antibacterial activity against E. coli was higher than against S. aureus.
Conclusion: Overall, enzymatic extraction, due to its specific degradation of the cell wall and preservation of sulfate and uronic acid functional groups, is the superior method for producing high-quality ulvan. Given the significant antioxidant and antimicrobial activities, ulvan extracted from U. rigida has high potential as a natural alternative to synthetic hydrocolloids and antioxidants in modern industrial formulations.

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Journal of Utilization and Cultivation of Aquatics

Articles in Press, Accepted Manuscript
Available Online from 30 June 2026

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