An investigation of ethanol inhibition and other limitations occurring during the fermentation of concentrated whey permeate by Kluyveromyces fragilis

Based on the well-known fact that K. fragilis strains show suboptimal performance when grown in concd. whey permeate, previously optimized medium was investigated for possible limitations appearing at high concns. Shaken flask cultures showed that no addnl. vitamin or mineral sources were required when the optimized amt. of yeast ext. was added to the concd. permeate. Several aspects of the EtOH [64-17-5] inhibition of the growth of K. fragilis NRRL 665 were investigated in continuous culture. The max. EtOH concn. tolerated by this yeast, i.e. 45 g/L, was much lower than commonly reported for other strains. EtOH and biomass prodn. were also influenced by the increased EtOH concn. of the medium. At 31 g/L of alc. product yield was reduced to 0.23 g/g whereas biomass yield was 0.05 g/g. Some evidence suggested that residence time and residual lactose concn. played a significant role in modulating the toxic effect of EtOH. [on SciFinder (R)]