Binding of calcium ions to polysaccharides from two freshwater microaigae, Palmelh teuensis (UTEX 1708) and Cosmatium turpinii (UTEX LB 1042) (PTP and CTP, respectively), and six industrial hydrocolloids was studied. The amount of bound calcium decreased with a decrease in pH below 6. Scatchard analysis showed that PTP, guar and locust bean had low calcium affinity and one type of binding site. Alginate bound calcium with the greatest affinity (k= 1.31 x 10h) among the hydrocolloids examined and appeared to have one type of binding site. Gum ardbic and CTP appeared to have two types of binding sites. The order of magnitude of uranic acid in each hydrocolloid did not agree with the order of calcium binding affinity as an intrinsic association constant indicating limited importance of the chemical nature of hydrocolloids to the effect of linear charge density.

Most strains of Butyrivibriofibrisolvens are known to produce extracellular polysaccharides (EPs). However, the rheological and functional properties of these EPs have not been determined. Initially, 26 strains of Butyrivibrio were screened for EP yield and apparent viscosities of cell-free supernatants. Yields ranged from <1.0 to 16.3 mg per 100 mg of glucose added to the culture. Viscosities ranged from 0.71 to 5.44 mPa s. Five strains (CF2d, CF3, CF3a, CE51, and H1Ob) were chosen for further screening. The apparent viscosity of the EP from each of these strains decreased by only 50 to 60% when the shear rate was increased from 20 to 1,000 S-. Strain CE51 produced the EP having the highest solution viscosity. A detailed comparison of shear dependency of the EP from strain CF3 with xanthan gum showed that this EP was less shear sensitive than xanthan gum and, at a shear rate of 1,000 s-, more viscous. EPs from strains CF3 and HlOb were soluble over a wide range of pH (1 to 13) in 80% (vol/vol) ethanol-water or in 1% (wt/vol) salt solutions. The pH of 1% EP solutions was between 4.5 and 5.5. Addition of acid increased solution viscosities, whereas addition of base decreased viscosity. EPs from strains CF3, CE51, and HlOb displayed qualitatively similar infrared spectra. Calcium and sodium were the most abundant minerals in the three EPs. The amounts of magnesium, calcium, and iron varied considerably among the EPs, but the potassium contents remained relatively constant.

An improved gas-chromatographic method for the simultaneous determination of neutral sugars and uranic acids in hydrocolloids or industrial gums was developed. The procedure involved methanolysis with OSM methanolic HCl followed by trimethylsilylation. This method was simplified over other deri,/atization methods to make it suitable for the routine analysis of hydrocolloids or other polysaccharides which contain uranic acids. The usefulness of this method was demonstrated by analysis of commercially available hydrocolloids. The described method was sensitive enough to identify some of the minor sugar components which were not easily identified by other derivatization methods.

The extracellular polysaccharides of two freshwater microalgae were examined as potential sources of hydrocolloids. A 0.10% solution of polysaccharide from Cosmarium turpinii (UTEX LB 1042) was pseudoplastic and more viscous than other selected hydrocolloids, indicating an ability to function as a thickening agent. The polysaccharide from Palmella teuensis (UTEX 1708) produced low-viscosity solutions and showed good pH (3.5 to 9.5) and temperature (20°C to 80°C) stability. A 1.00% solution of P. tewnsis polysaccharide showed Newtonian-like flow properties at low shear rate (2.25 set-' to 45 set-l). Fucose, xylose, galactose, glucose and glucuronic acid were found from the C. tulpinii polysaccharide, and only galactose was identified from the P. texensis polysaccharide.

Summary Extracellular polysaccharide (EPS) from Palmella texensis UTEX 1708 contained galactose as a sole sugar constituent. 1H‐NMR spectroscopy indicated the possibility of the presence of pyruvyl groups. Pyruvyl groups were also supported by the positive result of coloremetric assay. Methylation analysis before and after depyruvylation showed that a 2,3‐linked galactose was pyruvylated at the 4,6‐positions. Studies of trimethylsilyl (TMS) derivatives of methylglycosides on gas chromatography (GC) supported the 4,6‐position and the resulting fragmentation pattern on GC‐mass spectroscopy confirmed the presence of the pyruvic acetal, 4,6‐O‐(1‐carboxyethylidine)‐d‐galactose residue. The occurence of either galactan or pyruvylated galactose in green algae has not yet been reported.