title: Prediction of flocculation ability of brewing yeast inoculates by flow cytometry, proteome analysis, and mRNA profiling.
abstract: The ability of brewing yeast to flocculate is an important feature for brewing of qualitatively good beer. Flocculation involves two main cell wall structures, which are the flocculation proteins (flocculins) and mannans, to which these flocculins bind. Unfortunately, in practice, the flocculation ability may get lost after several repitches. Flow cytometry was employed to analyze glucose and mannose structures of the cell surface by application of fluorescent lectins. Validation of the expression of the flocculin genes Lg-FLO1, FLO1, FLO5, and FLO9 was carried out using microarray techniques. SDS-PAGE, western blot, and ESI-MS/MS analyses served to isolate and determine yeast cell flocculins. Mannose and glucose labeling with fluorescent lectins allowed differentiating powdery and flocculent yeast cells under laboratory conditions. Using microarray techniques and proteomics, the four flocculation genes Lg-FLO1, FLO1, FLO5, FLO9, and the protein Lg-Flo1p were identified as factors of major importance for flocculation. The expression of the genes was several times higher in flocculent yeast cells than in powdery ones. Flow cytometry is a fast and simple method to quantify the proportions of powdery and flocculent yeast cells in suspensions under defined cultivation conditions. However, differentiation under industrial conditions will require mRNA and protein expression profiling.
authors.affiliation: Helmholtz Centre for Environmental Research-UFZ, Department of Environmental Microbiology, Leipzig, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Heine
authors.forename: Frank
authors.initials: F
authors.lastname: Stahl
authors.forename: Heike
authors.initials: H
authors.lastname: Sträuber
authors.forename: Claudia
authors.initials: C
authors.lastname: Wiacek
authors.forename: Dirk
authors.initials: D
authors.lastname: Benndorf
authors.forename: Cornelia
authors.initials: C
authors.lastname: Repenning
authors.forename: Frank
authors.initials: F
authors.lastname: Schmidt
authors.forename: Thomas
authors.initials: T
authors.lastname: Scheper
authors.forename: Martin
authors.initials: M
authors.lastname: von Bergen
authors.forename: Hauke
authors.initials: H
authors.lastname: Harms
authors.forename: Susann
authors.initials: S
authors.lastname: Müller
mesh_terms: D001515:Beer / Q000382:microbiology*; D005427:Flocculation; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D005947:Glucose / Q000378:metabolism; D007218:Industrial Microbiology; D008358:Mannose / Q000378:metabolism; D037241:Mannose-Binding Lectins; D020411:Oligonucleotide Array Sequence Analysis; D020543:Proteome / Q000032:analysis / Q000378:metabolism; D040901:Proteomics; D012333:RNA, Messenger / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000378:metabolism*
chemical_list: C087578:FLO1 protein, S cerevisiae; D037241:Mannose-Binding Lectins; D020543:Proteome; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D005947:Glucose; D008358:Mannose