Influence of mixing and shear stress on Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii

Photosynthetic activity (PA) and growth of different microalgae species (Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii) depends in addition to other factors on mixing (tip speed) and shear stress (friction velocity) and was studied in a stirring tank (microcosm). In order to detect cause–effect relationships for an increase in photosynthetic activity, experiments were conducted under different pH values (6.0–8.5) and CO2 concentrations (0.038 and 4 % (v/v)). The PA was determined as the effective quantum yield by pulse amplitude modulation during a stepwise increase of the tip speed from 0 to 589 cm s−1 (friction velocity: 0–6.05 cm s−1) in short-term experiments. The increase caused a distinctive pattern of PA of each species. Compared to 0 cm s−1, C. vulgaris and S. obliquus showed a 4.0 and 4.8 % higher PA at the optimum tip speed of 126 cm s−1 (friction velocity of 2.09 cm s−1) and a 48 and 71 % higher growth, respectively. At 203 cm s−1, the PA dropped to the value of the unstirred control, while at 589 cm s−1, the PA decreased of up to 7 and 8 %. In contrast, C. reinhardtii showed 7 % stronger growth at 126 cm s−1, while the PA decreased about 15 % at an increase of tip speed to 589 cm s−1. For all investigated microalgae, the pattern of PA and higher growth was not only explained by the main contributing factors like light supply, nutrient supply, and overcoming diffusion gradients. The results indicate that hydrodynamic forces have a stimulating effect on the physiological processes within the cells.

[1]  Carl H. Gibson,et al.  Effects of small-scale turbulence on microalgae , 1990, Journal of Applied Phycology.

[2]  Y. Chisti,et al.  Shear rate in stirred tank and bubble column bioreactors , 2006 .

[3]  F. Colijn,et al.  In-line recording of PAM fluorescence of phytoplankton cultures as a new tool for studying effects of fluctuating nutrient supply on photosynthesis , 2001 .

[4]  Y. Chisti,et al.  Hydrodynamic Damage to Animal Cells , 2001, Critical reviews in biotechnology.

[5]  O. Björkman,et al.  Photon yield of O2 evolution and chlorophyll fluorescence characteristics at 77 K among vascular plants of diverse origins , 1987, Planta.

[6]  Pascal Jaouen,et al.  The shear stress of microalgal cell suspensions (Tetraselmis suecica) in tangential flow filtration systems: the role of pumps , 1999 .

[7]  Virendra S. Bisaria,et al.  Plant cell reactors—A perspective , 1989 .

[8]  Yusuf Chisti,et al.  Shear stress tolerance and biochemical characterization of Phaeodactylum tricornutum in quasi steady-state continuous culture in outdoor photobioreactors. , 2003 .

[9]  D. Wethey,et al.  Water flow influences oxygen transport and photosynthetic efficiency in corals , 2006, Coral Reefs.

[10]  K. Tanishita,et al.  Augmentation of microalgae growth due to hydrodynamic activation , 1995 .

[11]  H. Märkl,et al.  Hydrodynamic stress capacity of microorganisms , 1982, Biotechnology and bioengineering.

[12]  G. Gust,et al.  Solute release mechanisms from confined sediment cores in stirred benthic chambers and flume flows , 1992 .

[13]  E. Koch.  Hydrodynamics, diffusion-boundary layers and photosynthesis of the seagrasses Thalassia testudinum and Cymodocea nodosa , 1994 .

[14]  Daniel Chaumont,et al.  Cell fragility — The key problem of microalgae mass production in closed photobioreactors , 1991 .

[15]  René H. Wijffels,et al.  Effects of shear stress on the microalgae Chaetoceros muelleri , 2010, Bioprocess and biosystems engineering.

[16]  G. Gust,et al.  Phosphorus Entrainment Due to Resuspension in a Lowland River, Spree, NE Germany – A Laboratory Microcosm Study , 2007 .

[17]  J. Gavis,et al.  Transport limited nutrient uptake rates in Ditylum brightwellii1 , 1975 .

[18]  L. Thomsen,et al.  Sediment erosion thresholds and characteristics of resuspended aggregates on the western European continental margin , 2000 .

[19]  Contreras,et al.  Interaction between CO2-mass transfer, light availability, and hydrodynamic stress in the growth of phaeodactylum tricornutum in a concentric tube airlift photobioreactor , 1998, Biotechnology and bioengineering.

[20]  K. Tanishita,et al.  Effects of shear flow on photosynthesis in a dilute suspension of microalgae , 2004, Applied Microbiology and Biotechnology.

[21]  J. Merchuk,et al.  Shear effects on suspended cells. , 1991, Advances in biochemical engineering/biotechnology.

[22]  A. Carvalho,et al.  Microalgal Reactors: A Review of Enclosed System Designs and Performances , 2006, Biotechnology progress.

[23]  J. Briantais,et al.  The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence , 1989 .

[24]  J. Lumley,et al.  A First Course in Turbulence , 1972 .

[25]  Michael A. Borowitzka,et al.  Micro-algal biotechnology. , 1988 .

[26]  H. Schlichting.  Boundary Layer Theory , 1955 .

[27]  Yusuf Chisti,et al.  Effects of agitation on the microalgae Phaeodactylum tricornutum and Porphyridium cruentum , 2006, Bioprocess and biosystems engineering.

[28]  M. Borowitzka.  Commercial production of microalgae: ponds, tanks, tubes and fermenters , 1999 .