Quantitative analysis of straight-chain/branched-chain Ratio During Enzymatic Synthesis of Dextran Based on Periodate Oxidation

Abstract

The applications of dextran depend not only on the molecular weight but also on the types and number of branches. In this study, dextran generated from Leuconostoc mesenteroides (L.M.CICC-20724) was characterized by fourier-transform infrared spectrum and nuclear magnetic resonance spectroscopy. Our analyses showed that dextran was a polysaccharide composed of d-glucose units with predominantly α(1 → 6) linkages in the main chain and few α(1 → 3) linkages in the branch. Periodate oxidation, a classic chemical method, was usually combined with Smith degradation and gas chromatography to analyze glycosidic linkages in polysaccharide quantitatively. In this study, we calculated the exact straight-chain/branched-chain ratio in the dextran using periodate oxidation only. The ratios obtained by periodate oxidation only were compared to the ratios obtained by nuclear magnetic resonance. The results showed that the ratios of the two groups were nearly equal, and the average relative error between the two groups was 0.83%. This method was evaluated and found to be accurate and stable. This technique provided a convenient and straightforward chemical method for the quantitative analysis of the straight-chains and branched-chains in polysaccharides which had a similar structure. The ratios during the enzymatic synthesis process of dextran were analyzed by this method and were found to be stable with a high level of approximately 95% on average.