FLOCCULATION OF Kloeckera apiculata mc1 FROM WINE

MARTA ELENA FARÍAS; OSCAR ANTONIO SOSA; MARIA CRISTINA MANCA DE NADRA

USA

Congreso; 101th GENERAL MEETING AMERICAN SOCIETY FOR MICROBIOLOGY; 2001

ASM

Flocculation is the term used to describe the property expressed by certain yeasts, when they spontaneously aggregate to form flocs with sediment in the culture. Yeast flocculation has for many years been associated solely with brewing strains of Saccharomyces cerevisiae and S. carlsbergensis. Recently flocculation has been found in several other yeast genera: Hansenula, Kluyveromyces, Schizosaccharomyces and Zigosaccharomyces. The purpose of this study was to analyze flocculation and deflocculation of the yeast Kloeckera apiculata mc1, isolated from Argentinean wine, with the aim to understand the cell-cell interaction pattern. Flocculent cells of Kloeckera apiculata mc1 showed to possess intense cell-cell interactions. This behavior resulted in the formation of a coherent layer on the bottom when the yeast was grown in MYPG medium (0.5% malt extract, 1% yeast extract, 2% glucose, 2% peptone) pH 5.5 and incubated by shaking at 25ºC. After growth, the yeast was treated with deflocculating buffer (50 mM Na3PO4 ¨C 50 mM EDTA pH 7.5) and flocculated again in acetate buffer. Optimum flocculation was observed at pH 4.5 in the presence of 3 mM Ca2+. Flocculation stability depended on the sugars presence. Kloeckera apiculata mc1 flocculation was reversed by 50 mM galactose or lactose. Cell surface hydrophobicity was determined by microbial adhesion to hydrocarbons (MATH). The degree of hydrophobicity was approximately 15% for the different solvent (xylene, toluene and hexadecane) indicating that cell-cell interaction was not due to a non-specific binding. A fast cell flocculation was observed because of ¦Á-amylase treatment. The flocculation was found highly susceptible to pronase, chymotrypsine and proteases types IV and XXVII and was partially resistant to trypsin. These results suggest an important role of cell wall proteins in flocculent cells. Thus the mechanism of flocculation of Kloeckera apiculata mc1 is mediated by protein-carbohydrate interaction stabilized by Ca2+.