Discrimination by Heat and Proteinase Treatments between Flocculent Phenotypes Conferred on Saccharomyces cerevisiae by the Genes FLO1 and FLO5

Abstract

The effects of elevated temperature and of digestion with a variety of proteinases on the flocforming ability of flocculent strains of Saccharomyces cerevisiae, both genetically defined (FLO1 and FLO5) laboratory and genetically undefined brewing strains, have been determined. This has permitted classification of the flocculent phenotypes of these strains according to criteria other than quantitative grading of flocculence. The flocculent phenotypes conferred by both the FLO1 and the FLO5 gene were irreversibly lost upon treatment with pronase, proteinase K, trypsin or 2-mercaptoethanol treatments. However, the floc-forming ability of cells of the FLO1 strain ABXL-1D was destroyed by chymotrypsin digestion and was stable to incubation at 70 degrees C, whereas the floc-forming ability of cells of the FLO5 strain ABXR-11A was resistant to the action of chymotrypsin and was heat labile. Tetrad analysis of a cross of these FLO1 and FLO5 strains indicated that the chymotrypsin and heat sensitivity phenotypes were FLO-gene determined. It appears that expression of the FLO1 and FLO5 genes leads to the production of different and characteristic cell-wall proteins underlying their respective flocculent phenotypes.

Construction of hybrid yeasts with increased flocculation for white wine manufacture

“…The rate of flocculation was expressed on a subjective scale ranging from 0 to 4; where 0 indicated the absence of flocculation and 4 indicated extremely flocculent cells. Characterisation of the flocculation phenotype after heat and protease treatment was performed according to Hodgson et al (1985).…”

“…The flocculation of this strain is Ca 2+ , dependent and completely inhibited by EDTA. The properties of the flocculation phenotype of strain 21-45-10 were investigated by heat and protease treatment according to the methods of Hodgson et al (1985). These authors reported that flocculence conferred by the action of the FLO1 gene is easily distinguishable from that determined by the FLO5 gene.…”

Construction of Flocculent Yeast Cells (Saccharomyces cerevisiae) by Mating or Protoplast Fusion Using a Yeast Cell Containing the Flocculation GeneFL05

“…Heat treatment and chymotrypsin treatment of cells were done by the method of Hodgson et a/. 17 ) and the details were described previously. IS) Gentic methods.…”

Applications of yeast flocculation in biotechnological processes

“…It is well known that flocculent yeast cells are more resistant to protoplast formation than non-flocculent yeast cells [108]. Recombinant DNA methods have already been used to introduce several new properties into brewing yeasts such as the ability to degrade carbohydrates, modifications to the processes responsible for beer flavour production, and the already referred changes to yeast flocculation [109].…”