A dye binding assay for the quantification of soluble and cell-bound acidic polysaccharides produced by red algae

Polysaccharides produced in technical scale from red algae serve in a varie ty of industrial applications. Ruthenium red (RR) is a cytochemical stain w hich has been used to visualize these mostly acidic polysaccharides in ligh t microscopy. The binding of RR to algal polysaccharides is highly dependen t on the ionic strength of the surrounding medium. The dye is firmly bound at low ionic strength, but is released at increasing salt concentrations. T hese properties were exploited to develop a new method to quantify the amou nt of cell wall material synthesized by algal cells under different physiol ogical conditions. Soluble or extracted polysaccharides are quantified by a dot-blot procedure with subsequent image analysis, while cell-bound polysa ccharides are determined in situ by a dye-binding assay followed by photome try. In comparison to the current methods of quantification, the new assay is quick, reliable, and avoids extensive use of hazardous chemicals. (C) 19 99 Academic Press.