Effect of aeration rate on the alcoholic fermentation of whey by Kluyveromyces fragilis.

In this paper, the influence of aeration rate on the alcoholic batch fermentation of whey by Kluyveromyces fragilis NRRL Y-2415 was investigated. Assays in 1.5-L fermentor using concentrated whey permeate containing 100 g/L of lactose were carried out at different oxygen supply rate (KLaC*) from 0 to 82 mmol/Lh. Optimum response was obtained at 14 mmol/Lh: ethanol production rate reached was 3.4 g/Lh yielding 0.46 g of product per gram of initial lactose. An increase of KLaC* from 0 to 14 mmol/Lh improved the ethanol production: maximum specific ethanol production rate (qpm) increased 3.3 times from 0.3 to 1.0 g/gh. For higher aeration levels, ethanol production diminished and biomass formation was stimulated. The declination of qpm and the increase of microns at higher aeration level lead to conclude the importance of a controlled oxygen supply in order to obtain the required balance between yeast biosynthetic needs and ethanol production.