PELLICLE FORMATION AND ESTER PRODUCTION BY HANSENULA ANOMALA

Abstract

Three strains of Hansenula anomala, with different morphological and colony characteristics, were studied with respect to pellicle formation and ester production. Approximately the same amount of top cells was produced by each strain. The use of inhibitors of pellicle formation showed that, in the presence of the inhibitor, still cultures possessing no pellicle formed no ester, but that ester was produced in shaken cultures.With increased aeration, obtained by varying the surface–volume ratio, the peak of ester production occurred progressively earlier, but the maximum ester values attained in the various flasks did not vary much with the different degrees of aeration. In the 'train' fermentations, which assured almost complete ester recovery, one yeast strain produced equal amounts of ester in shaken and in still flasks as well as in 'foil-covered' flasks, whereas another strain gave lower ester values in the shaken flasks, probably because of stronger esterase activity. The results obtained indicated that as much, if not more, ester is produced with increasing aeration.