Polymer analytical characterization of glucan and mannan from yeast Saccharomyces cerevisiae

Samples of glucans and mannans isolated from yeast, Saccharomyces cerevisiae, were characterized using polymer analytical methods: C-13 and H-1 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 C-13 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 C-13 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.