Ethanol production from crude whey by Kluyveromyces marxianus

Kluyveromyces marxianus strain MTCC 1288 was employed to study the batch kinetics of ethanol and biomass production from crude whey. The yeast was able to metabolize most of the lactose within 22 h to give 2.10 g L−1 ethanol and 8.9 g L−1 biomass. The growth rate reached the peak value of 0.157 h−1 during the exponential phase but decreased significantly after the fermentation time of 12 h, presumably due to product inhibition. The specific ethanol formation rate attained the maximum value of 0.046 h−1 between 6 and 8 h of batch fermentation. The relationship between ethanol concentration and specific growth rate suggested a strong inhibitory effect of ethanol on the specific culture growth rate.