Controlled shear filtration: A novel technique for animal cell separation

Abstract

A novel rotary microfiltration technique specifically suited for the separation of animal cells has been developed. The concept allows the independent adjustment of wall shear stress, transmembrane pressure, and residence time, allowing straightforward optimization of the microfiltration process. By using a smooth, conically shaped rotor, it is possible to establish a controlled shear field in which animal cells experience a significant hydrodynamic lift away from the membrane surface. It is shown in preliminary experiments that shear‐induced cell‐rupture speeds up membrane clogging and that cell debris poses the most significant problem in harvesting of BHK cell cultures by dynamic microfiltration. However, a threshold value of shear stability exists which depends on the frequency of passing the shear field, the residence time in the shear field, as well as on cell status. By operating close to this threshold value, cell viability can be maintained while concentration polarization is efficiently minimized. By applying this concept, it is possible to attain flux rates several times higher compared to conventional crossflow filtration. Controlled shear filtration (CSF) can be used for batch harvesting as well as for cell retention in high cell density systems. In batch harvesting of hIL‐2 from rBHK cell culture, a constant flux rate of 290 L h−1 m−2 has been adjusted without indication of membrane clogging or fouling. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 663–674, 1999.

ALGINATE PRODUCTION BY Azotobacter vinelandii AS A VIRTUAL SENSOR TO ESTIMATE EFFECTIVE SHEAR RATE ON STIRRED TANK FERMENTERS

“…The amount of oxygen supplied varies from 1.68 gO2 (Calderbank and Moo-Young correlation) from 2.9 gO2 (Witchterle correlation). According to our virtual sensor, the correlations that model best the growth of A. vinelandii were those proposed by Withchterle et al (1984) and Vogel and Kroner (1999). This same tendency was observed in the cultures carried out at 200 rpm ( Fig.…”

“…Figur e 2c shows the apparent visc osit y of the cultur es c arried out at 340 rpm and it corresponds to t he s hear rat e obt ained i n figure 2a. W ith the c orrelati ons proposed b y Calderbank and Moo-Young ( 1959), Metzner and Ot to (1957), and B owen (1986) the apparent visc osit y is higher, w hile the l ower value of apparent viscosit y w as obt ained wit h correlations of W itcht erle et al (1984) and Vogel and Kroner (1999), therefor e, high k L a values c ould be exp ect ed when c ompared with t he other c orrelati ons.…”

“…The MMW of the alginate produced by the bacteria increased as OTRmax (at the beginning of the culture) decreased. For the cultures carried out at 340 rpm, the OTR max was 8.0 mmolO2h -1 L -1 , but when the alginate concentration was increased the OTR profiles likely followed the Witchterle et al (1984) correlation or the proposition made by Vogel and Kroner (1999). In this case, the maximum MMW of the alginate was obtained at 1.0 mmolO2h -1 L -1 and the MMW obtained was 1.08 x 10 6 g/gmol.…”

“…At 140 rpm, the total oxygen supplied to the culture through 80 hours of cultivations varies according to the shear rate correlation used, for example, wi th Calderbank and Moo-Young proposal (Calderbank and MooYoung, 1959), 1.3 gO2 are provided to the cultures, while the correlation proposed by Witchterle et al (1984) are supplied 3.63 gO 2. Figure 3a shows all the trial simulations of the virtual sensor and indicate that the Witchterle et al (1984) and Vogel and Kroner (1999) correlations could model better the growth of the bacteria. Figure 3b shows the results achieved with the virtual sensor in the cultures performed at 180 rpm after about 60 hours of cultivation.…”

Applications of membrane techniques for purification of natural products

“…Earlier work towards this objective includes the adoption of conical-shaped rotors (Vogel and Kroner 1999), cylindrical Taylor vortex systems (Parnham and Davis 1995), rotating disk filters (Lee et al 1995) and helical coiled Dean vortex devices (Luque et al 1999;Gehlert et al 1998). Recently, Auddy et al (2004) developed a stainless steel rectangular cross-flow cell that worked as a turbulence promoter to enhance the permeate flux in a nanofiltration system.…”