To better understand EPS chemical structure, further 2D NMR experiments were performed and results are presented inside the manuscript. In short, they allow to clearly identify the D-mannose α-(1→2) and α-(1→4) linkages in EPS. These results suggest they are the prevailing units of the EPS backbone making it a branched one. Also, β-glucopyranose and β-galactopyranose structures were identified and the acetylation was confirmed.
To my deep regret the structural characteristic of EPS is the weak point of this publication. Fourier transform infrared spectroscopy (FTIR) and NMR spectroscopy data can only be regarded as preliminary. According to the 1H NMR spectrum, it can be assumed that EPS has a complex branched structure. Probably, to establish its structure, it is necessary to use chemical methods (hydrolysis, methylation, etc. ), as well as two-dimensional NMR spectroscopy.