EFFECT OF CULTURE CONDITIONS OF KLUYVEROMYCES-MARXIANUS ON ITS AUTOLYSIS, AND PROCESS OPTIMIZATION

Cultivation of the lactose-metabolizing yeast Kluyveromyces marxianus var. marxianus (formerly K. fragilis) on supplemented whey permeate re sulted in cellular yield little affected by culture conditions in the ranges pH = 2.3-5 and T = 30-40 degrees C. When autolysis was induced only by energy source deficiency and thermal shock, cellular material solubilization depended slightly on autolysis temperature in the range T = 45-60 degrees C. On the contrary, the process was under tight con trol of culture conditions; when autolysis was carried out at 50 degre es C with an initial dry cellular concentration of 50 g l(-1), a clear optimum was observed for cells cultivated at pH = 4.5 and T = 35 degr ees C. So the critical step of the autolytic process consisted in bios ynthesis of lytic enzymes (during cell growth) rather than enzymatic p rogress (during autolysis). These results were compatible with a model previously proposed for Saccharomyces cerevisiae [1].