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New concepts for rapid yeast settling. II. pH switching with an inert powder
Author(s) -
Weeks M. G.,
Munro P. A.,
Spedding P. L.
Publication year - 1983
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260250307
Subject(s) - flocculation , settling , yeast , inert , fermentation , chemistry , suspension (topology) , saccharomyces cerevisiae , chemical engineering , settling time , chromatography , food science , biochemistry , environmental engineering , organic chemistry , environmental science , mathematics , control engineering , homotopy , step response , pure mathematics , engineering
A new technique is outlined for the rapid settling of yeast cells in fermentation media. The technique involved the addition of dense, inert particles (nickel powder) to a yeast suspension ( Saccharomyces cerevisiae ) at pH 4.5 and a rapid change of pH to 8.0–9.0. When the pH was changed large flocs formed immediately and settled rapidly, leaving a clear supernatant. On returning the pH to 4.5 the flocs were destroyed. This technique gave larger flocs and higher settling rates than the constant pH method, and much lower nickel/yeast ratios were required. Good flocculation also occurred in a fermentation medium. The technique was used to recycle yeast cells to a semicontinuous ethanol fermentation. Application of the technique to this and similar systems is discussed. The factors affecting yeast/inert powder flocculation are also discussed and a model is proposed to explain the observed experimental behavior for flocculation with a rapid change in pH.