Chemical composition and potential for utilization of the marine alga Rhizoclonium sp.

This paper reports on the feasibility of utilizing the abundant marine alga Rhizoclonium as a substitute for wood fiber, based on studies on its morphology and chemical composition. The alga appears as wood fiber-like filaments consisting of tubular end-to-end connections of individual cells. In the population studied, each cell averaged 82 mu m long, 76 mu m wide and had cell wall 7.4 mu m thick. The composition was 15.9% ash, 9.72% extractable by 90% acetone, 9.43% extractable by alcohol-benzene, 3.8% acid insoluble fraction, 17.8% pentosan, 36.3% 1% NaOH soluble fraction and 57.4% carbohydrate. The composition of its carbohydrates is similar to that of wood fiber. After hydrolysis, reduction, and acetylation of the sugars, and GC-MS analysis the components showed glucose (65.8%), xylose (19.8%), galactose (12.5%) and mannose (1.3%). There were high contents of cold- and hot-water extractables, 31.1% and 34.6%, respectively. These consisted of xylose, galactose and glucose. The crystallinity index (CI%) of its holocellulose was as high as 86.5%, close to the 90.5% value of wood fiber. The 1091 cm(-1) peak intensity increased with reaction cycles, suggesting decreasing absorptivity and increasing crystallinity. This corresponds to terrestrial plant fibers. Taken together, these features suggest that Rhizoclonium has good potential as a raw material for pulp.