초록
<P><B>Abstract</B></P><P><B>BACKGROUND:</B> The bioconversion of whey into ethanol by immobilized <I>Kluyveromyces marxianus</I> in packed‐bed and fluidized bioreactors is described. Both batch and continuous cultures were analyzed using three different strains of <I>K. marxianus</I> and the effect of the operating mode, temperature, and dilution rates (D) were investigated.</P><P><B>RESULTS:</B> All immobilized strains of <I>K. marxianus</I> (CBS 6556, CCT 4086, and CCT 2653) produced similar high yields of ethanol (0.44 ± 0.01 g EtOH g<SUP>−1</SUP> sugar). Significant variations of conversion efficiencies (66.1 to 83.3%) and ethanol productivities (0.78 to 0.96 g L<SUP>−1</SUP> h<SUP>−1</SUP>) were observed in the experiments with strain <I>K. marxianus</I> CBS 6556 at different temperatures. High yields of ethanol were obtained in fluidized and packed‐bed bioreactors continuous cultures at different D (0.1 to 0.3 h<SUP>−1</SUP>), with the highest productivity (3.5 g L<SUP>−1</SUP> h<SUP>−1</SUP>) observed for D = 0.3 h<SUP>−1</SUP> in the fluidized bioreactor (87% of the maximal theoretical conversion), whereas the highest ethanol concentration in the streaming effluent (28 g L<SUP>−1</SUP>) was obtained for D = 0.1 h<SUP>−1</SUP>. Electronic micrographs of the gel beads showed efficient cell immobilization.</P><P><B>CONCLUSION:</B> Batch and continuous cultivations of immobilized <I>K. marxianus</I> in fluidized and packed‐bed bioreactors enable high yields and productivities of ethanol from whey. Copyright © 2012 Society of Chemical Industry</P>