High-Quality Agar Polysaccharide from Unexplored Gelidium micropterum Kützing Biomass

The agar is an important polysaccharide widely used in the food industry, pharmaceuticals, cosmetics, microbiology, and molecular biology applications. The global demand for agar polysaccharide is steadily rising, but its production is limited due to shortage of good raw material. This research investigates the potential of Gelidium micropterum as an alternative and sustainable source of high-quality agar. Agar was extracted using different concentrations of NaOH (4, 6, 8, and 10% w/v) and without NaOH treatment. The resulting agar yields ranged from 16.97% to 26.03%, with corresponding gel strengths between 855 ± 51 and 2078 ± 55 g/cm². Notably, 8% and 10% NaOH pre-treatments yielded agar with superior gel strength and thermal properties, surpassing those reported for other Gelidiales species under similar conditions. Structural characterisation was performed using FT-IR, ¹³C-NMR, and ¹H-NMR spectroscopy, confirming similarities with standard agar. The extracted agar's molecular weights were in the range of 5704-7276 kDa. Sulphate content varied from 0.175 ± 0.082% to 6.197 ± 0.446% across treatments. The agar also supported microbial growth at lower concentrations than commercial agar, indicating promising application potential. These findings highlight G. micropterum as a promising, sustainable option for expanding agar resources.