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STUDY OF THE PHENOMENON OF AGGLOMERATION IN THE YEAST SACCHAROMYCES CEREVISIAE
Author(s) -
Guinard JeanXavier,
Lewis Michael J.
Publication year - 1993
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1993.tb01189.x
Subject(s) - saccharomyces cerevisiae , yeast , economies of agglomeration , fermentation , chemistry , biochemistry , flocculation , strain (injury) , industrial fermentation , food science , biology , chemical engineering , organic chemistry , anatomy , engineering
Agglomeration or “grittiness” is detrimental to bakers' yeast quality. Gritty yeast only partially resuspends when mixed in water, most of it remaining as macroscopic cell aggregates. A macroscopic sedimentation test was developed for measuring agglomeration intensity. Expression of the gritty phenotype was investigated in two strains (N176 and GB1) of Saccharomyces cerevisiae grown on a 14‐liter scale by varying fermentation conditions of agitation and aeration. Results show that yeast agglomeration is different from yeast flocculation, and is determined by both strain genetic background and environmental factors. The gritty phenotype was expressed in the strain prone to agglomeration (N176) when dissolved oxygen was limiting in the fermenter. Gritty cells had a lower phosphorus and lipid concentration and a higher protein concentration at the surface of the cell, and a higher amount of whole cell and cell wall proteins and calcium than non‐gritty cells. Some proteins were also extracted from gritty cells with sodium hydroxide or mercaptoethanol, that were not present in non‐gritty cells. Agglomeration did not result in major differences in the structure or composition of the structural cell wall mannoprotein (CWMP). A model for agglomeration is proposed: proteins (cognors) activated by Ca 2+ (cofactors) to increase their binding capacity bind the mannans (cognons) of adjoining cells; binding is facilitated by the lower phosphorus and lipid concentration at the surface of gritty cells.