Polymer analytical characterization of glucan and mannan from yeastSaccharomyces cerevisiae

Samples of glucans and mannans isolated from yeast, Saccharomyces cerevisiae, were characterized using polymer analytical methods: 13C and 1H NMR spectroscopy, IR spectroscopy and light scattering coupled with size exclusion chromatography (SEC/MALLS). Despite partially incomplete reactions, high-molar-mass mannans with a trimodal distribution were obtained with all the enzyme systems. Mannoprotein with a molar mass of 410 000 g mol–1 was obtained using a recombinant glucanase that was completely void of protease activity. Chemically extracted mannans had molar masses of 21 000–62 000 g mol–1, whereas enzymatically isolated mannans had molar masses between 64 000 and 112 000 g mol–1. The native structure of the mannans was damaged by acids and alkalis in chemical extraction. Mannans that were isolated with protease after 6–7 h had molar masses from 116 000–190 000 g mol–1. Here the protein matrix was not completely hydrolysed. Glucan exhibited the 6 signals of the ring C atoms in the 13C NMR spectrum, and in the IR spectrum the typical mannan bands at 820 cm–1 had disappeared. The degree of substitution of the synthesized CM-glucans (CM = carboxymethyl), which was determined by 13C NMR spectroscopy, had values ranging from DS = 0.5–1. In curdlan derivatives, depending upon the synthesis, over 90% degradation was found for the phosphatization, whereas in the carboxymethylation of barley glucan the degradation was only 15–35%. The glucan derivatives of the baker's yeast investigated have higher molar masses than those of the spent brewer's yeast investigated. CM-glucans synthesized from yeast had a bimodal distribution. This was not observed for CM-curdlan. Reacting the cell walls with an enzyme cocktail (EC3) at pH = 9 was intended to suppress the glucanase activity in favour of protease activity, so as to achieve high-molar-mass glucan. However, the molar masses of 65 000–100 000 g mol–1 from the CM-glucans synthesized in this way showed that the glucanase activity could only be partially suppressed.