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Microbial and algal alginate gelation characterized by magnetic resonance

Fabich, Hilary T., Vogt, Sarah J., Sherick, Matthew L., Seymour, Joseph D., Brown, Jennifer R., Franklin, Michael J., Codd, Sarah L.
Journal of biotechnology 2012 v.161 no.3 pp. 320-327
Pseudomonas aeruginosa, alginate gels, alginates, biopolymers, biotechnology, calcium, chemical structure, gelation, image analysis, ions, mutants
Advanced magnetic resonance (MR) relaxation and diffusion correlation measurements and imaging provide a means to non-invasively monitor gelation for biotechnology applications. In this study, MR is used to characterize physical gelation of three alginates with distinct chemical structures; an algal alginate, which is not O-acetylated but contains poly guluronate (G) blocks, bacterial alginate from Pseudomonas aeruginosa, which does not have poly-G blocks, but is O-acetylated at the C2 and/or C3 of the mannuronate residues, and alginate from a P. aeruginosa mutant that lacks O-acetyl groups. The MR data indicate that diffusion-reaction front gelation with Ca²⁺ ions generates gels of different bulk homogeneities dependent on the alginate structure. Shorter spin–spin T₂ magnetic relaxation times in the alginate gels that lack O-acetyl groups indicate stronger molecular interaction between the water and biopolymer. The data characterize gel differences over a hierarchy of scales from molecular to system size.