Effect of culture conditions of Kluyveromyces marxianus on its autolysis, and process optimization

Abstract

Cultivation of the lactose-metabolizing yeast Kluyveromyces marxianus var. marxianus (formerly K.␣fragilis) on supplemented whey permeate resulted in cellular yield little affected by culture conditions in the ranges pH = 2.3–5 and T = 30–40 °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 °C. On the contrary, the process was under tight control of culture conditions; when autolysis was carried out at 50 °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 °C. So the critical step of the autolytic process consisted in biosynthesis of lytic enzymes (during cell growth) rather than enzymatic progress (during autolysis).

These results were compatible with a model previously proposed for Saccharomyces cerevisiae [1].