PHYSIOLOGICAL CONSEQUENCES OF POLYPLOIDY IN YEASTS - III. Influence of Alcohol on the Glucose Metabolism of the Diploid and Autotetraploid Brewery Yeasts

Abstract

1. The  interesting  discovery  in  this  laboratory  that  the  tetraploid  yeast  shows  an  accelerated  rate  of  fermentation  though  producing  only  the  same  percentage  of  alcohol  as  the  diploid  necessitated  a  series  of  investigations  on  the  effect  of  alcohol  in  the  medium  on  glucose  utilisation  under  comparable  conditions.
2. An  analysis  of  the  results  indicates  that  the  quality  of  the  pitch  influences  the  performance  of  both  the  diploid  and  the  autotetraploid.  The  actual  percentage  of  sugar  metabolized  at  any  given  level  of  alcohol  is  higher  in  the  case  of  the  tetraploid  but  this  does  not  necessarily  imply  that  it  has  a  higher  alcohol  tolerance  than  the  diploid.  This  difference  in  the  actual  glucose  consumed  is  demonstrated  to  be  due  only  to  the  differing  fermenting  abilities  of  the  two  strains.
3. The  necessity  for  a  redefinition  of  alcohol  tolerance  is  discussed.  The  only  reliable  method  of  ascertaining  the  alcohol  tolerance  is  to  study  the  performance  of  the  yeast  in  regular  fermentation  trials.
4. The  relative  alcohol  tolerance  of  the  two  strains  depends  on  the  physiological  condition  of  the  cells.  Storage  for  different  periods  produces  different  effects  on  the  diploid  and  the  autoletraploid.