Preparation of galactans from Gracilaria debilis and Gracilaria salicornia (Gracilariales, Rhodophyta) of Indian waters

Superior quality non-methylated and low-sulphated galactans were extracted from two Indian agarophytes namely Gracilaria debilis and G. salicornia growing naturally along the west coast of India, using an eco-friendly method developed in our laboratory. The galactans were characterised by FT-IR, C-13 NMR, GC-MS, ICP, GPC and rheological measurements. G. debilis produced exclusively non-methylated galactan exhibiting the greatest gel strength of 650 +/- 25 g cm(-2) and lowest sulphate of 0.21 +/- 0.06%. On the contrary, G. salicornia polysaccharide was composed of non-methylated galactose (major) and mannose (minor), having gel strength of 510 +/- 25 g cm(-2) and sulphate of 0.45 +/- 0.06%. Very low heavy metal contents were determined in both the galactan samples, which may thus be potentially useful in food and biological applications.