Extraction, Characterization of Phycocolloides, Evaluation of Toxicity and Developing a Film from Gracilaria hikkaduwensis: An Underutilized Sri Lankan Seaweed

Background: Seaweed-derived phycocolloids are widely employed in various industries due to their unique physico-chemical properties. Despite the global usage of seaweeds, the family Glacilariaceae is not adequately explored for phycocolloid extraction in Sri Lanka. The present study aimed at extraction and characterization of phycocolloids from G. hikkaduwensis from Sri Lanka. Methods : Phycocolloids were extracted from G. hikkaduwensis using a hot water extraction method and characterized for their physico-chemical properties. Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet (UV) absorption, setting and melting points, proximate composition, and sulphate content analysis using the BaCl₂-gelatin method were conducted. The in vivo toxicity of the extracted phycocolloids was evaluated using the Artemia salina toxicity assay. A film was developed with phycocolloids and characterization including solubility, water vapor transmittance rate (WVTR), water vapor permeability (WVP), water content, transparency, and light absorbance analysis were performed. The extraction resulted in a yield of 23.4±0.2% (w/w) of phycocolloids with a low sulphate content of 6.22±0.10%, as confirmed by FTIR analysis. UV absorption analysis indicated good separation from impurities. The setting and melting temperatures were recorded as 40.5ºC and 87ºC, respectively, comparable to commercial agar, while the pH was acidic. Proximate composition analysis reflected favorable properties with high carbohydrate content and low moisture, ash, protein, and fat contents. The A. salina toxicity assay confirmed the non-toxic nature of the extracted phycocolloids, highlighting their potential for safe application in various industries. The extracted phycocolloids formed wet films with a thickness of 0.46±0.04 mm, high water content, high WVTR, low solubility, and low WVP, making them suitable for application. Upon drying, the film exhibited a reduced thickness of 0.32±0.08 mm, lower water content, and increased solubility. Light absorbance analysis demonstrated potential UV barrier properties. Conclusion: The present study thus unveiled a potential and underutilised source of phycocolloids, G. hikkaduwensis, which is endemic to Sri Lanka. Further studies are underway to utilise the phycocolloids and phycocolloids film in any industrial application.