Effects of Hydrodynamic and Interfacial Forces on Plant Cell Suspension Systems

Shake flasks are widely used in biotechnological process research. Bioprocesses for which hydromechanical stress may become the rate controlling parameter include those where oils are applied as carbon sources, biotransformation of compounds with low solubility in the aqueous phase, or processes employing animal, plant, or filamentous microorganisms. In this study, the maximum local energy dissipation rate as the measure for hydromechanical stress is characterized in shake flasks by measuring the maximum stable drop size. The theoretical basis for the method is that the maximum stable drop diameter in a coalescence inhibited liquid/liquid dispersion is only a function of the maximum local energy dissipation rate and not of the dispersing apparatus. The maximum local energy dissipation rate is obtained by comparing the drop diameters in shake flasks to those in a stirred tank reactor. At the same volumetric power consumption, the maximum energy dissipation rate in shake flasks is about 10 times lower than in stirred tank reactors explaining the common observation of considerable differences in the morphology of hydromechanically sensitive cells between these two reactor types. At the same volumetric power consumption, the maximum local energy dissipation rate in baffled and in unbaffled shake flasks is very similar. A correlation is presented to quantify the maximum local energy dissipation rate in shake flasks as a function of the operating conditions. Non-negligible drop viscosity may be considered by known literature correlations. Further, from dispersion experiments a critical Reynolds number of about 60,000 is proposed for turbulent flow in unbaffled shake flasks.

Section: Introductionmentioning

confidence: 99%

Hydromechanical stress in shake flasks: Correlation for the maximum local energy dissipation rate

Peter

Suzuki

Büchs

2006

“…Shear stress effects on undifferentiated plant cells have been studied in different bioreactor types (Kieran et al, 2000). Various approaches to measure the effect of shear stress on cell growth have been used; notably the viability of cells (Hooker et al, 1989;Zhong et al, 1994), and the production of secondary metabolites (Takeda et al, 1998;Zhong et al, 1994).…”

mentioning

confidence: 99%

Effects from shear stress on morphology and growth of early stages of Norway spruce somatic embryos

Sun

Aidun

Egertsdotter

2009

The shear stress effect on directional expansion of pro embryogenic masses (PEMs) and suspensor cell development of somatic embryos of Norway spruce (Picea abies) at the proliferation stage was studied by a direct and quantitative image analysis system. The experimental system allowed for detailed observations of the effect of hydrodynamic shear stress in rotating and deforming liquid cultures of proliferating Norway spruce somatic embryos. Briefly, somatic embryos at an early development stage comprised only of clusters of meristematic cells without suspensor cells were fixed on an alginate film. The alginate film was affixed on the bottom of a flow cell and the somatic embryos were subjected to laminar flow through the chamber of the flow cell. Magnified images of the cell clusters were collected every 24 h. The image data was processed based on a normalized cross-correlation method, capable of measuring morphological and size features of individual cell clusters in both temporal and spatial domains. No suspensor cells developed in the cell clusters under shear stress of 140 s(-1) for the duration of the experiments. Cell clusters in the control cultured in stationary liquid conditions developed suspensor cells after 5-9 days in culture. Furthermore, the radial growth of meristematic cell clusters was inhibited by shear rates of 86 and 140 s(-1), corresponding to shear stress of 0.086 and 0.14 N/m(2), compared to growth under stationary conditions. The shear rate showed a significant negative correlation to growth rate. Control group showed no preference for direction during growth under static conditions.

“…Based on previous work on the impact of turbulence on biomaterials (Yim and Ayazi Shamlou, 2000;Henzler, 2000;Kieran et al, 2000), it was hypothesised that the physical properties of the precipitated flocs at the end of the ageing process were determined primarily by the total fluid stress, E f , acting on the flocs during the conditioning stage. Assuming that fluid stress is equal, or directly proportional to, the fluid energy dissipated in the liquid by the impeller, then E f was defined as the product of the power input by the impeller, P, per unit volume of suspension, V, and the ageing (conditioning) time, t. Thus, E f ‫ס‬ v t ‫ס‬ [(P/V)t].…”

Section: Precipitationmentioning

confidence: 99%

Ultra scale‐down approach for the prediction of full‐scale recovery of ovine polycolonal immunoglobulins used in the manufacture of snake venom‐specific Fab fragment

Neal

Christie²,

Keshavarz-Moore

et al. 2002

In this article, we describe a new approach that allows the prediction of the performance of a large-scale integrated process for the primary recovery of a therapeutic antibody from an analysis of the individual unit operations and their interactions in an ultra scale-down mimic of the process. The recovery process consisted of four distinct unit operations. Using the new approach we defined the important engineering parameters in each operation that impacted the overall recovery process and in each case verified its effect by a combination of modelling and experimentation. Immunoglobulins were precipitated from large volumes of dilute blood plasma and the precipitated flocs were recovered by centrifugal separation from the liquor containing contaminating proteins, including albumin. The fluid mechanical forces acting on the precipitate and the time of exposure to these forces were used to define a time-integrated fluid stress. This was used as a scaling factor to predict the properties of the precipitated flocs at large scale. In the case of centrifugation, the performance of a full-scale disc stack centrifuge was predicted. This was achieved from a computational fluid dynamics (CFD) analysis of the flow field in the centrifuge coupled with experimental data obtained from the precipitated immunoglobulin flocs using the scale-down precipitation tank, a rotating shear device, and a standard swing-out rotor centrifuge operating under defined conditions. In this way, the performance of the individual unit operations, and their linkage, was successfully analysed from a combination of modelling and experiments. These experiments required only millilitre quantities of the process material. The overall performance of the large-scale process was predicted by tracking the changes in physical and biological properties of the key components in the system, including the size distribution of the antibody precipitates and antibody activity through the individual unit operations in the ultra scale-down process flowsheet.