Chemical structure and quality of agars from Gracilaria

Abstract

Agar polymers synthesized by species of the genus Gracilaria constitute a complex mixture of molecules, containing several extremes in structure. Sulphate hemi-esters, methyl ethers and pyruvic ketals can alter in a number of ways the structural regularity of agar based on strictly 3-O-linked /I-L-galactopyranose and 4-O-linked a-L-galactopyranose residues. In comparison with agars from Gelidium and Pterocladia, agars from Gracilaria can have higher degrees of sulphation, methoxylation and pyruvylation. The gelling ability of agars from most of Gracilaria species is considerably improved by adopting, before extraction, an alkali pretreatment which converts a-L-galactose 6 sulphate into 3,6-anhydro-a-L-galactose. Native agars obtained from Gracilaria cannot be classified, with few exceptions, as bacteriological grade agar as they have a high content of methoxyls and consequently high gelling temperatures. On the contrary, the genus Gracilaria is considered the most important source of food and sugar-reactive grade agars.Among techniques which can be used to study algal polysaccharides, combined H and 3 C nuclear magnetic resonance spectroscopy represent the most effective and powerful method for the investigation of the chemical structure of agarocolloids.

Investigation of the role of a β(1–4) agarase produced by Pseudoalteromonas gracilis B9 in eliciting disease symptoms in the red alga Gracilaria gracilis

“…Gracilaria species are of great economic importance since they are the source of two important grades of agar, namely food grade and sugar reactive agar (Armisen, 1995;Murano, 1995). Since the 1950s, South Africa has benefited substantially from the export of Gracilaria gracilis that occurs naturally in Saldanha Bay (Anderson et al, 1989).…”

Influence of temperature, light and nutrients on the growth rates of the macroalga Gracilaria domingensis in synthetic seawater using experimental design

“…For example, metabolites with different pharmacological activities such as carotenoids, mycosporines, lipids, and polysaccharides have been identified in algae (Cardozo et al 2007;. Within the red macroalgae, the genus Gracilaria, represented by more than 100 species (Oliveira and Plastino 1994) living in warm water areas (Steentoft and Farham 1997), is notable for its economic importance as a source of agar (Murano 1995;Gressler et al 2010). In general, the Gracilaria species have been studied at the physiological, biochemical, and Electronic supplementary material The online version of this article (doi:10.1007/s10811-012-9797-1) contains supplementary material, which is available to authorized users.…”

Effect of dark and salinity treatment in the yield and quality of agar from Gracilaria cornea (Rhodophyceae)

“…7773/cm.v28i3.223 (Rhodophyceae); es usado ampliamente como aditivo alimenticio y en numerosas aplicaciones biotecnológicas, médicas y farmacéuticas. Las unidades repetitivas pueden estar sustituidas en mayor o menor grado por grupos sulfatos, metilos y piruvatos (Murano, 1995). La cantidad y localización de estos grupos sustituyentes en la molécula, además de factores medioambientales y diferentes procedimientos de extracción, pueden influir en la calidad del agar obtenido (Lignell y Pedersén, 1989;Lahaye y Rochas, 1991).…”