Design of a horizontal-dual bladed bioreactor for low shear stress to improve hydrodynamic responses in cell cultures: A pilot study in Chlamydomonas reinhardtii

Emre Taylan Duman^a,b, Ayse Kose^a, Yunus Celik^a, Yunus Celik^a

Department of Bioengineering, Faculty of Engineering, University of Ege, 35100, Bornova, Izmir, Turkey.

Abstract

The aim of this study is to investigate the potential of a novel design considering low shear horizontal bioreactor (LSB-R) with counter rotation U-shape impellers. Bioreactors (LSB-R and STR) were compared under the same mixing time (23 ± 2 s) using Computational Fluid Dynamics analysis focusing on the shear stresses. The highest shear stress was around the impeller tips with an average shear stress found to reach up to 0.8 Pa for LSB-R a very small value compared to the 100-fold increase inside the STR. Cell wall deficient and motility impaired mutants of Chlamydomonas were used in the experiments to see the effects of shear stress on growth and morphology. Biomass productivities were almost doubled, and specific growth rates were increased by LSB-R. On the other hand, the motility impaired cells aligned as colonies to protect from shear forces in STR and a rapid death occurred in cells with flagella due to continuous deflagellation and cell damage. The results indicate that; LSB-R design has great advantage on lowering shear stress, eliminating excessive hydrodynamic forces, providing mild operation conditions.

Keywords: Bioreactor, Shear stress, Bioprocess, CFD, Chlamydomonas.