507 / 2018-09-13 15:40:41

Catalytic Conversion of Chitosan to Amino Acid

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Chitin is the second abundant biopolymer on earth, but it has not been extensively investigated compared to cellulose till now. [1] Chitin and its derivative chitosan are promising feedstocks containing 7 wt% biologically-fixed nitrogen, which have shown the potential to produce 3-acetamido-5-acetylfuran, 2-aceyamido-2-deoxysorbitol, glucosamine (GlcN), 2-methyl pyrazine, pyrrole, and glucosaminic acid (GlcNA). [2] Among these, GlcNA has attracted attention because it can be widely used in asymmetric synthesis, industry, medicine, and food fields. High yield of GlcNA could be obtained by oxidation of pure GlcN-HCl over metal or metal oxide, such as Pd-Bi/C, Au/MgO, and HgO. Till now, there is no report about the conversion of chitosan to GlcNA so far.
In this work, we demonstrate the production of GlcNA from chitosan employing commercial solid acid catalysts for chitosan hydrolysis to glucosamine (GlcN) and subsequent oxidation of GlcN to GlcNA over gold-based catalysts. For chitosan hydrolysis, we show a considerable yield of GlcN (58%) could be achieved using Amberlyst-15 at 160 oC. As for the oxidation of pure GlcN-HCl, GlcNA yield is strongly depended on the support and Au/MgO exhibits best activity. The direct oxidation of chitosan-hydrolyzed GlcN is tested and 10% GlcNA is obtained. We clarify the removal of humins derived during hydrolysis reaction by activation carbon (AC) adsorption. A two-step process has been developed to producing GlcNA from chitosan and the overall yield is up to 22%.


[1] N. Yan, X. Chen, Nature 2015, 524, 155-157.
[2] X. Chen, H. Y. Yang, N. Yan, Chem. - Eur. J. 2016, 22, 13402-13421.