Dynamics of yeast immobilized-cell fluidized-bed bioreactors systems in ethanol fermentation from lactose-hydrolyzed whey and whey permeate

We studied the dynamics of ethanol production on lactose-hydrolyzed whey (LHW) and lactose-hydrolyzed whey permeate (LHWP) in batch fluidized-bed bioreactors using single and co-cultures of immobilized cells of industrial strains of Saccharomyces cerevisiae and non-industrial strains of Kluyveromyces marxianus. Although the co-culture of S. cerevisiae CAT-1 and K. marxianus CCT 4086 produced two- to fourfold the ethanol productivity of single cultures of S. cerevisiae, the single cultures of the K. marxianus CCT 4086 produced the best results in both media (YEtOH/S = 0.47–0.49 g g−1 and QP = 1.39–1.68 g L−1 h−1, in LHW and LHWP, respectively). Ethanol production on concentrated LHWP (180 g L−1) reached 79.1 g L−1, with yields of 0.46 g g−1 for K. marxianus CCT 4086 cultures. Repeated batches of fluidized-bed bioreactor on concentrated LHWP led to increased ethanol productivity, reaching 2.8 g L−1 h−1.