Optimization of Yield and Chemical Properties of Agar Extracted from Melanothamnus Somalensis from Oman Sea

Abstract

The red seaweed Melanothamnus somalensis was investigated as potential economic source of agar. The effect of different conditions of alkali pre-treatment on chemical properties of agar was evaluated. Agar was extracted by various concentrations of NaOH (4%, 6% and 8%) and heated at different temperatures (70 °C, 75 °C and 80 °C) for different durations (2 h, 2.75 h and 3.5 h). The yields-molecular weight (M W) and sulfate contents of extracted agar were analysed and characterized by FTIR spectroscopy. The yield was significantly increased at these treatments from 23.29% to 30.86%. M W studied by HPLC ranged from (12.45 ± 0.21) × 10 5 to (8.60 ± 2.40) × 10 5 Da. FTIR bands show sulfate groups in C4 and C6 of galactose and no sulfate group were found on both C2 of galactose and C2 of 3,6-anhydrogalactose. All treatments showed a high sulfate content that ranged from 5.4% to 10.1%. These properties were found to be significantly affected by the alkali pre-treatment concentration (p < 0.05). In conclusion, agar extracted in this study was considered acceptable for industrial application and the optimal conditions for extraction were found to be at 6% NaOH at 70 °C for 2 hours.