phenotype with Ca2+ ions required for the correct conformation of the zymolectins. Co-flocculation between Kluyveromyces and Schizosaccharomyces has been shown to be by a “lectinic” mechanism. This theory explains the essential role of calcium and how deproteinisation affects flocculation. Flocculation zymolectins and phenotypes Three flocculation phenotypes have been elucidated based on the zymolectins they produce: Flo1 (Stratford and Assinder, 1991) NewFlo (Stratford and Assinder, 1991) and Mannose Insensitive (MI). These flocculation phenotypes differ in the time of the onset of flocculation and the sugar inhibition of flocculation. The genetic control of yeast flocculation has not been extensively studied. Recent reports suggest genes encoding lectin-like proteins exhibit close sequence homology. Furthermore, it seems that FLO genes have interchangeable functions that can compensate for one another. Flocculation phenotypes The Flo1 phenotype is inhibited by mannose occurs in both ale and lager strains. The NewFlo phenotype differs from that of Flo1 in several ways. Firstly NewFlo flocculation is inhibited by mannose, glucose and maltose. Secondly the NewFlo lectin is putatively encoded by the FLO10 gene. Studies by the Speers group have indicated little change in zymolectin levels through a fermentation. It is argued that lectin maturation occurs some fourteen hours after the cessation of cell division and is therefore not concomitant with entry into stationary phase, although this is strain dependent. However the molecular proof of this maturation is near non-existent. The picture is complicated by changes in cell surface hydrophobicity and CO2 driven shear which confounds flocculation measurements often erroneously solely attributed to zymolectin interactions. While flocculation (clumping and settling) occurs at this time, this flocculation occurs as a result of changes in hydrophobicity and a decline in shear due to which is in turn to low CO2 evolution. References Brewing