Nutritional composition and alginate characteristics of Sargassum polycystum (C. Agardh, 1824) growth in Sebesi island coastal, Lampung-Indonesia

Macro and micro-nutrient as well as alginate characteristics from Sargassum polycystum (C. Agardh, 1824) brown seaweed growth in Sebesi Island were investigated. Gravimetry was used to determine the macro nutrients and Atomic Absorption Spectroscopy (AAS) to identify the micro nutrients. While, alginate extraction followed the acid extraction protocol, Nuclear Magnetic Resonance (NMR) was utilized to determine M/G ratio. The results of this research showed a descending percentage of macro nutrients as follows: Carbohydrate > Ash > Moisture > Crude Fibre > Protein > Fat. The descending presence of micro nutrients was: Manganese (Mn)> Barium (Ba)> Zinc (Zn)> Iron (Fe)> Copper (Cu)> Selenium (Se)> Molybdenum (Mo). The yields of extracted alginate were high (24.18-29.59%) and consisted of high moisture and an ash content of 12.16 +/- 0.4 and 24.37 +/- 0.5 respectively. The pH was 7.28 +/- 0.05, the viscosity 195.7 +/- 8.4, whiteness and gel strength were about 58.19 +/- 0.6 and 60.23 +/- 0.7. The ratio of Maluronate and Guluronate (M/G) blocks varied between 1.04-1.48. Based on the results of the canonical correspondence analysis (CCA), the main character of alginates such as the M/G ratio and the gel strength could be associated with variations in the composition of DO and ammonia, while viscosity was related to variations of nitrate and phosphate. It can be concluded that the growth of S. polycystum on the coast of Sebesi Island can be recommended as alginate resource with robust quality.