Influence of the dilution rate on the bioproductivity of lactose-utilizing yeasts: fuzzy logic modeling

The studied problem is of commercial interest because whey, the cultivation substrate, is a waste by-product from the transformation of milk into cheese and casein. Investigations on the influence of the dilution rate (D) on the bioproductivity of lactose-utilizing yeasts were carried out with two model strains--the oxidative strain Candida blankii 35 and the fermentative strain Candida pseudotropicalis 11. The increase of D led to the different changes in productivity. The best synthesizing ability of both continuously cultivated strains is established at D = 0.4 h-1] despite the different type of metabolism. The oxidative strain C. blankii 35 is more effective in comparison with the fermentative strain C. pseudotropicalis 11 because of its ability to synthesize 1.5 fold higher biomass and protein yields. These experimental facts were proved also by simulative research with a Fuzzy Knowledge-Based System (FKBS) developed for modeling the influence of D on several process variables.