Characterization of the structural properties of mannoproteins isolated from selected yeast-based products upon the enzymatic treatment

Abstract

Four types of yeast-based products (baker's yeast, brewer's yeast, Agrimos® and YCW-b) were subjected to Zymolyase® enzymatic treatment to isolate mannoproteins. In addition to their health promoting properties, yeast-based mannoproteins exhibit high emulsifying and stabilizing properties and play a crucial role in the vinification process. Upon purification, two mannoprotein populations were recovered including a high molecular weight (MP1, 36–620 kDa) composed of a variety of mannoproteins with different mannan to protein ratio (2.5–10), and a low molecular weight (MP2, 2.3–6.8 kDa) being identified as a monocomponent. α-(1,6) Mannanase treatment revealed the presence of α-(1,6) mannose linkages in the high MW MP1 population, but not in the low MW MP2 population. The isolated mannoproteins MP1 were mainly O-glycosylated. Mannoprotein structures were further characterized by 1D and 2D NMR, 7 anomeric carbons were determined in Agrimos® MP1, four of them have very similar chemical shifts than those of mannan standard. The proportion of α-(1,6) linked mannan was found to be the highest in the Agrimos® MP1. The thermal conformational changes of mannoproteins in both solid and liquid states were revealed by FTIR.