A new fractionation method for kappa- and lambda-carrageenans isolated from Gigartina pistillata (Rhodophyta)
Gigartina pistillata (GMELIN) STACKHOUSE harvested commercially along the
Atlantic coast of Morocco is generally a mixture of gametophytes with a cell wall enriched
in κ-carrageenan, and tetrasporophytes with a wall composed mainly of λ-carrageenan.
In order to separate both polysaccharides, two extraction methods were investigated.
The first one involved sequential extraction in water with increasing temperatures
in 20 °C increments starting from 20 °C up to 100 °C. The second method was carried out
by using successive ethanol concentrations (100, 80, 60, 40, 20 % and water). Chemical
characterization of the different fractions revealed that low extraction temperatures or
high ethanol concentrations contained mainly the κ-carrageenan. In contrast, high extraction
temperatures or low ethanol concentrations yielded λ-carrageenan enriched fractions.
These results demonstrate that the use of these distinct methods can selectively extract
κ- or λ-carrageenans to improve the quality of the final carrageenan product and increase
the value of raw algal material in Morocco.
