Chemical composition of the Australian bull kelp, Durvillea potatorum

Abstract

The chemical composition of the Australian bull kelp, Durvillea potatorum, was determined. As a percentage of the whole stipe dry weight, components were: Crude fibre, 57.40 %; alginic acid, 35.15 % ; "cellulosic" polysaccharide, 22.61 % ; laminarin, 1.79 %; mannitol, 3.20%; nitrogen, 1.21 %; ash, 28.09 %; insoluble ash, 8.81 %; Ca²⁺, 1.47%; Mg²⁺, 0.44%; Na⁺, 1.45%; K⁺, 3.36%; PO₄^2-, 5.15%; Cl^-, 5.87%; SO₄^-, 3.49 %; I^-, 0.25%; and chlorophyll, 0.01 %.

Tissue fractionation showed that the peripheral layer contained approximately two-thirds of the total chlorophyll and three-quarters of the total phenolic compounds, but only one-tenth of the total alginic acid. In whole stipes up to two-thirds of the alginic acid was in a soluble form.