The Applicability of Enzymes in Cellulose Ether Analysis

Six methyl cellulose (MC) samples, one with a IDS Of 1.32 and five with a DS between 1.83 and 1.88, were degraded with five different enzymes or enzyme preparations containing endoglucanases. The main goal was to investigate whether enzymes could be used for determination of heterogeneity of the substituent distribution along the cellulose chain. To obtain information about the heterogeneity it was necessary to gather information on how the enzymes affect hydrolysis. Monomer composition and methyl distribution in the polymer chain were analyzed after total or partial random hydrolysis and appropriate derivatization by GC and MS, respectively, and used as reference data for the evaluation of the enzymatic hydrolysis. Size exclusion chromatography with multi angle light scattering and refractive index detection (SEC-MALLS/RI) was used to estimate molar mass distribution of the MCs before and after hydrolysis. Electrospray and matrix assisted laser desorption/ionization (ESI and MALDI) in combination with various MS analyzers were compared with respect to quantification of the degradation products directly and after perdeuteromethylation. Methyl group distribution in the oligomeric fractions and the average DS/DP were calculated from ESI mass spectra. With help of the reference analysis, patterns could be corrected for the unspecific contribution of end groups. By labelling and ESI-MSn, our knowledge about the tolerance of the enzyme's sub-sites with respect to the number of methyl groups could be improved. A novel standard addition method in combination with electrospray ionization ion trap mass spectrometry (ESI-IT MS) was used to determine the amount of formed oligomers.