Permeation into yeasts

Weichherz was apparently the first to utilize the concept that permeation can be treated as a reversible unimolecular reaction. However his equations assume a direct one-step relation between permeation into yeast cells by glucose and the liberation of carbon dioxide. But it seems that several steps intervene, four or probably several more. The sigmoid curves observed by Nord and others for this end result seem to result from phos-phorylated processes occurring when glucose penetrates the yeast cell. 

Whey permeate was obtained by ultrafiltration of cottage-cheese whey and supplemented with yeast extract in a membrane bioreactor (Mehaia and Cherian, 1986). The lactose in the permeate was converted into lactic... 

A great deal of attention has been directed to the anaerobic fermentation by yeasts, notably Saccharomyces cerevisiae in its various forms (top and bottom brewers and bakers yeast). This has been industrially important, and the subspherical cells, about 6-8 /n in diameter, are produced under standard conditions. They can be brought into suspension with little or no clumping. They are then suitable for tests of the permeation through the surface of the suspended cells. From the discussion on pages 9-13, it follows that permeation can be treated either as the diffusion into spheres, where there is no semipermeable plasma membrane, or as the unidimensional diffusion through a relatively thin, slightly permeable membrane, with substantial complete diffusion of permeant. Since there is every reason to assume the latter case, the former case is considered unimportant. 

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