FLOCCULATION ONSET, GROWTH-PHASE, AND GENEALOGICAL AGE IN SACCHAROMYCES-CEREVISIAE

Flocculation onset, the time during the fermentative cycle at which th e strains of Saccharomyces cerevisiae become flocculent, is an importa nt factor in the brewing industry. The flocculation ability of Flo1 ph enotype (strain NCYC 869) remained practically unchanged throughout th e growth and seems to be insensitive to the presence of nutrients of t he culture medium. On the contrary, the flocculation of NewFlo phenoty pe (strain NCYC 1195) exhibited a cyclic behaviour. It was found that the loss of flocculation in the early growth was the result of two com bined effects: the dismantling of the flocculation mechanism of the ce lls coming from the inoculum and the nonflocculent state of the new ce lls produced after growth has started. The onset of flocculation of st rain NCYC 1195 in the cultural conditions used in this work coincided with the end of the exponential growth, when the minimum glucose level in the culture medium was attained. It was demonstrated that it is po ssible to manipulate the flocculation onset by changing the initial gl ucose concentration in the culture medium.