Agar from vegetative and tetrasporic <i>Gelidiella acerosa</i> (Gelidiales, Rhodophyta)

Abstract

Agar yield and properties were determined from vegetative and tetrasporic Gelidiella acerosa collected from two localities on the northwestern coast of Luzon Island, Philippines. Occurrence and percent abundance of the different life stages confirmed spatial and temporal variations in reproductive periodicity. Agar was extracted using acetic acid pretreatment and steam pressure. Vegetative plants yielded a higher agar content with a high gel strength which could be related to the biochemical changes in the wall matrix polysaccharide composition of the thalli relative to its physiological state. Agar yield did not vary significantly between sites, while gel strength varied significantly between sites and with life stage. No definite trend was observed in the gelling and melting temperatures. A relatively low percent sulfate content (range=.6-2.2%) was measured in all samples, while 3,6-anhydrogalactose contents were slightly higher in tetrasporic (range=41.7-49.7%) compared to vegetative (range=41.6-46.6%) plants. In this agarophyte, there seemed to be either another chemical variable that affected the physical gel properties or molecular variations (molecular weight and length) in the heterogenous polysaccharides that compose each specific life stage.