Extraction and characterization of agar from Australian Pterocladia lucida

Abstract

Polysaccharides were sequentially extracted from Australian Pterocladia lucida at 50°C, to give the Warm Water (WW) fraction, and at 95°C. The 95°C extract was further separated into gelling (GF) and thaw water (TW) fractions by freezing-thawing. Fourier Transform infrared (FTIR) spectroscopy, compositional and linkage analyses, and physico-chemical properties indicated that the GF contained an agar with nearly idealized repeating structure and low levels of sulfate and pyruvate substitution. By contrast, the WW and TW contained heterogeneous, highly sulfated galactans with relatively low levels of 3,6-anhydrogalactose and higher levels of pyruvate and glycosyl branching and impurities, such..