Physical studies of cell flocculation

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This application describes a research program designed to further understand the phenomenon of cell flocculation.  The flocculation or "clumping" properties of cells are important in beer and other fermentations.  For example, the flocculation characteristics of brewing yeasts are of prime of concern when brewers select production strains.  Excessively flocculent strains may prevent complete fermentations while poorly flocculent strains may also cause filtration and flavour problems.  The "clumping" properties of cell are also important in various other biotechnological industries, as flocculation is a major method of cell separation.  It is generally accepted that the extent of yeast flocculation is due in part of antibody-like substances (or zymolectins) present on the yeast cell wall that bind to sugars on adjacent yeast cells, akin to a 'molecular velcro(TM)'.  The rate and extent of cell flocculation are also strongly dependent on the type and magnitude of fluid mixing of the yeast suspensions as well as their cell size.  Recently, we have confirmed the importance of 1) yeast surface chemistry, 2) the chemical nature of the wort or beer the yeast is surrounded by and 3) the fluid mixing that occurs in fermentation. It is planned to computer model the movement of the zymolectins and the sugars during binding. Using a specialized instrument it is also planned to determine cell wall properties of individual yeast cells. Additionally, a comparison of flocculation behaviour industrial fermenters will be undertaken to confirm laboratory findings. Also, in collaboration other researchers we also plan to continue development of a micron scale "flocculation chip" to measure the force to disrupt zymolectin-sugar bonds between yeast cells. Successful funding of the above research program will permit further understanding of how cells flocculate.  The extrapolation of these findings to other colloidal food systems will be of academic, technical and economic value to the food and biotechnology industries.