Controlled expression of the dominant flocculation genes FLO1, FLO5, and FLO11 in Saccharomyces cerevisiae.
In many industrial fermentation processes, the Saccharomyces cerevisiae yeast should ideally meet two partially conflicting demands. During fermentation, a high suspended yeast count is required to maintain a satisfactory rate of fermentation, while at completion, efficient settling is desired to enhance product clarification and recovery. In most fermentation industries, currently used starter cultures do not satisfy this ideal, probably because nonflocculent yeast strains were selected to avoid fermentation problems. In this paper, we assess molecular strategies to optimize the flocculation behavior of S. cerevisiae. For this purpose, the chromosomal copies of three dominant flocculation genes, FLO1, FLO5, and FLO11, of the haploid nonflocculent, noninvasive, and non-flor-forming S. cerevisiae FY23 strain were placed under the transcriptional control of the promoters of the ADH2 and HSP30 genes. All six promoter-gene combinations resulted in specific flocculation behaviors in terms of timing and intensity. The strategy resulted in stable expression patterns providing a platform for the direct comparison and assessment of the specific impact of the expression of individual dominant FLO genes with regard to cell wall characteristics, such as hydrophobicity, biofilm formation, and substrate adhesion properties. The data also clearly demonstrate that the flocculation behavior of yeast strains can be tightly controlled and fine-tuned to satisfy specific industrial requirements.
Govender
Patrick
P
Department of Biochemistry, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa.
Domingo
Jody L
JL
Bester
Michael C
MC
Pretorius
Isak S
IS
Bauer
Florian F
FF
D000426:Alcohol Dehydrogenase / Q000235:genetics; D018441:Biofilms / Q000254:growth & development; D002473:Cell Wall / Q000737:chemistry; D005427:Flocculation; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D050890:HSP30 Heat-Shock Proteins / Q000235:genetics; D057927:Hydrophobic and Hydrophilic Interactions; D007218:Industrial Microbiology / Q000379:methods; D037102:Lectins; D008358:Mannose / Q000378:metabolism; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis* / Q000235:genetics
C087578:FLO1 protein, S cerevisiae; C110690:FLO11 protein, S cerevisiae; C103472:FLO5 protein, S cerevisiae; D050890:HSP30 Heat-Shock Proteins; C494390:HSP30 protein, S cerevisiae; D037102:Lectins; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C509911:ADH2 protein, S cerevisiae; D000426:Alcohol Dehydrogenase; D005947:Glucose; D008358:Mannose