Depolymerization alginate

Preparation of metal-depolymerized alginate solutions was carried out as above, without the addition of NaOD. Eight samples of 1, 2,4, 8, 12, 16, 20, and 24% metal loadings were prepared. 

Depolymerized Alginic Acid Solution NMR Studies. Studies are being conducted with depolymerized alginic acid. In these samples, the MG blocks were removed by acid hydrolysis lea dng shorter chains contmning mostly GG or MM blocks. For whole alginic acid, complexation of one ion to a GG block leads to a zipper effect. If two or more metal ions bind to GG blocks that are separated by one... 

Figure 7. NMR spectra of a) sodium-alginate and b) sodium-depolymerized alginate.

Figure 8. Percent metal ion loading versus normalize peak intensity for calcium-depolymerized alginate. GG blocks MM blocks...

In the sodium depolymerized alginic acid sample, Figure 10, some resolution of the signals is possible. Through studies of GG and MM homopolymeric samples, it is possible to attribute the signals occurring at 67 ppm and -53 ppm to G-residues. 

Figure 11, CPMAS NMR spectrum of calcium-depolymerized alginate.

Preliminary studies of depolymerized alginic acid indicate that the GG-preference of the divalent alkaline earths remains in mixtures of homopolymeric blocks. One conclusion from our data might be that there is a minimum chain length required for maximum metal ion binding. Until further studies are completed, the extent of binding for the divalent ions and depolymerized alginate cannot be determined. 

The viscosity of alginate solutions decreases with increasing temperature, but provided the temperature is not maintained at high levels for extended periods, the viscosity decrease is reversible. Partial depolymerization of the alginate occurs if solutions are exposed to excessive temperatures or to sufficiendy elevated temperatures for extended periods. 

Radiation has been shown to be a feasible way to convert higher DP alginates to lower DP alginates with improved properties (King, 1994). Loss of t accompanying such depolymerizations can transform pseudoplastic fluids to Newtonian fluids. In carrageenans, radiolysis was shown to be initially rapid and then to decrease to a constant, low, radiation-insensitive DP the rate was faster in solution than in the solid state (Marrs, 1988). 

Alternatively, encapsulation in alginate beads, either directly after isolation (Guo et al. 1989), even as primary culture for several months (Hauselmann et al. 1994), or after expansion in monolayers (Bonaven-ture et al. 1994), offers the opportunity to recover the chondrocytes later by depolymerization of the alginate. 

Alginic acid dispersions are susceptible to microbial spoilage on storage, which may result in some depolymerization and hence a decrease in viscosity. Dispersions should therefore be preserved with an antimicrobial preservative such as benzoic acid potassium sorbate sodium benzoate sorbic acid or paraben. Concentrations of 0.1-0.2% are usually used. 

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