Mass transfer effects on the reaction rate for heterogeneously distributed immobilized yeast cells

Research output: Contribution to journalArticle


Here we examine the efficiency of different immobilized cell gradients applied to immobilized Saccharomyces cerevisiae fermenting glucose to ethanol. We developed a simulation model to fully study the competing effects of mass transfer hindrance and kinetics. It is based on a diffusion-reaction model and can be used to analyze the different cell concentration profiles inside an immobilized gel bead, in terms of effectiveness factors, productivity, and mass flux. The internal diffusion coefficient, which varies with the local cell concentration, as well as the external mass transfer, is taken into account when describing the efficiency. Although the diffusion hindrance is greater at higher cell concentrations, high cell concentration is still advantageous in the present case because the increase in reaction rate outweighs the diffusion hindrance. Thus, high cell concentrations contribute to increased productivity. The influence of the cell concentration gradient on the efficiency of the beads is negligible, Within the range of cell profiles studied it has been established that the location of the cells within the bead is of lesser importance. However, a steep cell gradient increases the importance of the external mass transfer. (C) 2002 Wiley Periodicals, Inc.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Chemical Engineering


  • cell concentration gradient, variable, simulation, immobilized yeast cells, diffusion, mass transfer
Original languageEnglish
Pages (from-to)664-673
JournalBiotechnology and Bioengineering
Issue number6
Publication statusPublished - 2002
Publication categoryResearch