EFFECT OF SOME PHYSICOCHEMICAL TREATMENTS ON THE KINETICS OF AUTOLYSED-YEAST EXTRACT PRODUCTION FROM WHEY

In this work, the effects of salt and mechanical cell breaking on the overall activity of the endogenous enzymes of Kluyveromyces fragilis g rown on whey-based media were studied at the optimal values of tempera ture (54 degrees C) and initial concentration of yeast and whey protei n (100 g dm(-3)) previously selected. An unstructured kinetic model of first order was found to be capable of simulating quite satisfactoril y the time course of residual suspended solids (Y) in the slurry, as w ell as Kjeldahl (KP) and Lowry (LP) protein and total carbohydrates (G ) accumulation in the clear extract. The autolysis kinetic rate consta nt (k(a)), and yield factors for Kjeldahl and Lowry protein and reduci ng sugars on total solids hydrolysed were found to be insensitive to t he salt level and preliminary mechanical disruption of cells. Neverthe less, maximum production of yeast-whey protein extracts was achieved w hen the endogenous enzymes of ground cells are induced by 5% w/v salt addition. Except for their respective salt contents, both autolysates exhibited no apparent difference in chemical composition.