Casillo, Angela

University of Naples Federico II (Italy)



Bacterial mannan polysaccharide: chemical structure and conformational studies


Many microorganisms are known to produce extracellular polysaccharide. Bacterial EPSs usually occur as capsule and/ormedium released polysaccharides. EPSs are involved in several biological functions, such as bacteria adhesion to surface andbiofilm formation, ion sequestering, and protection from desiccation. Furthermore, the enhanced production of a high-molecular-weight polyanionic EPS at sub-optimal incubation temperatures lends support to theories that EPS may serve as acryoprotectant for microorganisms as well as their enzymes. The cryoprotectant role of EPS was established in the psychrophilicbacterium Colwellia psychrerythraea 34H grown at low temperatures). The EPS from the psychrotolerant bacteriumPseudoalteromonas could enhance the stability of the cold-adapted protease secreted by the same strain by preventing itsautolysis, avoiding enzyme diffusion, and helping the strain in enriching the proteinaceous particles and trace metals in thedeep-sea environment. The chemical characterization of these polymers is the starting point for obtaining relationshipsbetween their structures and their various functions. Here, the chemical structure and conformational studies of a mannanexopolysaccharide from the bacterium Psychrobacter arcticus strain 273-4 isolated from permafrost is presented. The mannanfrom the cold-adapted bacterium was compared with its dephosphorylated derivative and the commercial product fromSaccharomyces cerevisiae. Starting from the chemical structure a new approach through various physicochemical techniques todeepen the study of the structure/activity relationship was explored. Finally, the ice recrystallization inhibition activity of thepolysaccharides is reported.

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