Extraction and characterization of alginate from brown seaweed (Sargassum wightii) and its hydrolysis.

Present study reveals the ultrasound assisted extraction and characterization of alginate from brown seaweed (Sargassum wightii). Further, production optimization and characterization of alginate lyase from Lactobacillus casei was carried out. Subsequently produced alginate lyase was used for the hydrolysis of alginate. Ultrasound-assisted extraction gave a higher yield (13.7g/50gm) of alginate than dilute acid extraction (0.0773g/100g) from Sargassum wightii powder. Extracted alginate exhibited the moisture, ash, protein, fat, carbohydrate and uronic acid content was 14.22%, 30.22%, 0.57%, 0.84%, 53.67% and 270.76mg/g, respectively. This result confirms successful relative purity of the extracted alginate. FTIR analysis revealed sodium alginate backbone of sample. Extracted alginate showed a higher b* value (27.26), indicating yellowness compared to standard alginate. The DSC thermogram exhibited a single sharp endothermic peak with an onset temperature (Tₒ) of approximately 134.35°C, a peak temperature (Tₚ) at 135.13°C, and an end temperature of 136.07°C. Five Lactobacillus strains (Lactobacillus acidolacti, Lactobacillus plantarum, Lactobacillus plantarum sub species, Lactobacillus casei, and Lactobacillus pentasus) were evaluated for the production of alginate lyase enzymes. Amongst, Lactobacillus casei (19.2 U/ml) and Lactobacillus plantarum sub species (19.01 U/ml) illustrated the higher production of alginate lyase enzyme. For maximum production of alginate lyase enzyme from Lactobacillus casei showed the optimum conditions such as 24 hour as fermentation time, 1.5% of alginate as substrate, 2% sucrose as carbon source, and 2% yeast extract as nitrogen source for maximum production of alginate lyase enzyme. Produced lyase enzyme showed the optimum at pH 8 and 37 oC temperatures. Further, hydrolysis of alginate was performed using the produced alginate lyase enzyme, the result showed the conversion of alginate into its oligosaccharides fraction as evidence by Thin Layer Chromatography (TLC). Therefore, the present investigation highlights the potential of brown seaweed as a valuable resource for the production of alginate and its value-added derivatives through alginate lyase enzyme from Lactobacillus casei.