Effective diffusion coefficients and bioconversion rates of inhibitory compounds in flocs of Saccharomyces cerevisiae

Abstract Background Fermentation strategies for bioethanol production which use flocculating Saccharomyces cerevisiae yeast need to account for the mechanism by which inhibitory compounds, generated in the hydrolysis of lignocellulosic materials, are tolerated and detoxified by a yeast floc. Results Diffusion coefficients and first-order kinetic bioconversion rate coefficients were measured for three fermentation inhibitory compounds (furfural, hydroxymethylfurfural and vanillin) in self-aggregated flocs of S. cerevisiae NRRL Y-265. Thiele-type moduli and internal effectiveness factors were obtained by simulating a simple steady-state spherical floc model. Conclusions The obtained values for the Thiele moduli and internal effectiveness factors showed that the bioconversion rate of the inhibitory compounds is the dominant phenomenon over the mass transfer inside the flocs.