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Obtaining Hexoses from Chitosan through Depolymerization with Nitrous Acid.

BACKGROUND AND OBJECTIVE
Residues from shrimp farming have a great potential for sugar production and, consequently, an increase in the production of derivatives for the low-carbon chemical industry. Obtaining bioactives from chitosan has been extensively investigated using different methodologies. The purpose of this work was to study the chitosan depolymerization reaction aiming at the production of monomers without the use of additional enzymes or mineral acids.


MATERIALS AND METHODS
In this work, we systematically study the effect of sodium nitrite concentration and reaction conditions (pH and temperature ranges) in acetic acid solvent on the chitosan depolymerization reaction aiming at the production of monomers, specifically 2,5-anhydromannose, without the use of additional enzymes or mineral acids.


RESULTS
The results indicated that only a small range of reaction conditions and nitrite concentrations allow for obtaining the monomer, while in most combinations of these parameters, oligomers are obtained. We found that the temperature decisively affects the reaction yield, with the attainment of 2,5-anhydromannose favored at lower temperatures.


CONCLUSION
The method proved to be simple and easy to perform allowing to obtain 2,5-anhydromannose with low-cost reagents. This monomer can be converted into several derivatives for industrial application (5-Hydroxymethylfurfural, ethanol, etc.).