Polissacarideos da parede celular de levedura de cervejaria (Saccharomyces cerevisiae), obtida por rompimento mecanico da celula e de processo industrial de autolise

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

The cell wall of yeast (S. cerevisiae) from industrial beer fermentation is composed of polissacharides which can be utilized in the food and others industries. Considerable information about the chemical structure of cell wall polissacharides of S. cerevisiae is related in the literature and was obtained from laboratory cell cultures grown in synthetic media. The aim of this work was to establish a parallel between the fractionation routine, the yield of each fraction and their compositions, using two commercial sources of raw material: a) residual yeast cells from industrial beer fermentation; b) residual cell wall material from the production of yeast extract, with autolysis of the cells referred to in item a. The rupture of the yeast cells was carried out in a pilot glass ball mill (Dyno Mill);this operation was optimized and reached near 95% of cell disruption. The fractionation design for the sequential separation of the fractions obtained from the cell wall, allowed for the isolation of virtually homogeneous purified fractions and the polysaccharide component s of each one could then be determined and indirectly their ocurrence in the original fractions. Each fraction was quantified, characterized chemically and identified structurally. The samples were subjected to GC-MS, 13C NMR and IR spectroscopy in order to determine the structure. The cell wall obtained mechanical rupture showed a yield of 30% of the dry cell weight. The purified polissacharide fractions of cell walls obtained from the mechanical rupture of cells and from the cell walls of industrial residues showed, respectively, the following yields in dry weight related to the cell wall: 16.7 and 11.2% of glycoprotein; 7.1 and 7.8% of mannan; 0.8 and 1.0% of alkali soluble glucan; 59.2 and 63.8% of insoluble glucan and 1.8 and 2.2% of acid soluble glucan. From the glycoprotein four subfractions were isolated with yields of: 1.3 and 2.7 %, fraction A; 56.3 and 44.2%, fraction B; 10.5 and 12.0 %, fraction C and 10.6 and 12.7 %, fraction D. The three quantitatively main fractions of cell wall polissacharides were glycoprotein, manan and insoluble glucan. The polissacharide of the former two fractions was confirmed as 2-O-substituted α-D- (1->6) mannopyranan with α-D-(1-»2) mannopyranosidic branches and a non- reducing terminal unit of α-D-(1->3) mannopyranoside; the insoluble glucan being β-D-(1->3) glucopyranan. From the subfractionation of the glycoprotein using Cetavlon, the polissacharide of the most abundant subtraction (B) showed a structure identical to that of the mannan fraction. The RNA present in the cell wall was almost totally found in subtraction A, practically eliminated this compound from the other fractions and subtractions. The cell wall byproduct from industrial autolysis, showed almost the same general characteristics when compared to that from mechanical rupture, i.e., even when exposed to native and others enzymes during autolysis, it was basically preserved, although a different behaviour with respect to solubilization and dispersion during the fractionation procedures was observed. This work consolidates in one publication some new information together with information already described but in a fragmented form and obtained under a variety of conditions.

ASSUNTO(S)

saccharomyces cerevisiae glicoproteinas parede celular manana levedos glucanas polissacarideos

ACESSO AO ARTIGO

Documentos Relacionados