Biofluidization

Although NMR spectrometers of operating frequencies > 400 MHz are cosdy and require specialist technical support staff, the technique provides a broad picture of the chemical modifications arising from the reactions of free radicals or related oxidants in complex, multicomponent systems such as intact biofluids, tissue sample... 

The detection and quantification of one or more of the above lipid peroxidation produas (primary and/or secondary) in appropriate biofluids and tissue samples serves to provide indices of lipid peroxidation both in ntro and in vivo. However, it must be stressed that it is absolutely essential to ensure that the products monitored do not arise artifactually, a very difiScult task since parameters such as the availability of catalytic trace metal ions and O2, temperature and exposure to light are all capable of promoting the oxidative deterioration of PUFAs. Indeed, one sensible precaution involves the treatment of samples for analysis with sufficient levels of a chainbreaking antioxidant [for example, butylated hydroxy-toluene (BHT)] immediately after collection to retard or prevent peroxidation occurring during periods of storage or preparation. 

Herz, H., Blake, D.R and Grootveld, M. (1994). Multicomponent investigations of the hydrogen peroxide- and hydroxyl radical-scavenging antioxidant capacities of biofluids the roles of endogenous pyruvate and lactate. Free Rad. Res. Commun. (in press). 

Silica-based restricted access materials (RAM) have been developed for cleanup in bioanalysis, first for low molecular weight compounds in biofluids (Rbeida et al., 2005) and subsequently for biopolymers such as peptides (Wagner et al., 2002). A classification of different types of RAM has been given by Boos and Rudolphi (1997). Novel RAMs with strong cation-exchange functionality have been synthesized and implemented in the sample cleanup of biofluids. Racaityte et al. (2000) have shown that this type of RAM is highly suitable for the online extraction and analysis of... 

Tseng H-M, Li Y, Barrett DA (2007) Profiling of amine metabolites in human biofluids by micellar electrokinetic chromatography with laser-induced fluorescence detection. Anal Bioanal Chem 388 433-439... 

Keywords Biofluids Chemosensors Emission spectroscopy Mechanosensors Optical properties Polarity Rheology Twisted intramolecular charge transfer Viscosity... 

Akers W, Haidekker MA (2005) Precision assessment of biofluid viscosity measurements using molecular rotors. J Biomech Eng 127(3)450-454... 

This section of the current chapter goes beyond a simple listing of current three-phase biofluidization applications to consider the differences in conventional three-phase fluidization and biofluidization from the aspect of reactor design and operation. Past research into three-phase biofluidization has been summarized in several excellent reviews (Andrews, 1988 Fan, 1989 Heijnen et al., 1989 Schiigerl, 1989 Siegel and Robinson, 1992), and this chapter will concentrate on the main research themes and advances of the last few years. Though gas continuous three-phase fluidized bioreactors exist (Fan, 1989), we consider here only those bioreactors in which the liquid phase is the continuous phase. 

Table 14a. Recent Three-Phase Biofluidization Research on Treatment of Municipal Wastewater...

Several areas are receiving much of the research attention. Approaches that integrate product recovery with the fermentation in a three-phase fluidized bed bioreactor reflect general research trends in biochemical engineering (Yabannavar and Wang, 1991 Davison and Thompson, 1992). The successful use of three-phase biofluidization has also been demonstrated for recombinant protein systems, where it may have some benefit in improving plasmid stability (Shu and Yang, 1996). 

Table 15. Recent Applications of Three-Phase Biofluidization to Fermentation Processes...

Biofilm Effects. Particle size and density are especially important in determining the success of biofluidization. Bioparticle size and density are determined by the initial particle properties, the extent of biomass growth, and biofilm density. For a biofilm covered support, the apparent particle density is determined by Eq. (7) (Fan, 1989). 

In a study of the effect of electrolyte concentration on gas holdup, Bly and Worden (1990) found a strong effect. A salt solution resulted in twice the gas holdup that distilled water did under otherwise identical operating conditions, because the salt solution suppressed bubble coalescence. Investigation of this phenomenon is important in biofluidization, because biological media commonly have high electrolyte concentrations. 

The above is true for nonbiological fluidization as well as for biofluidization. An important difference is the changing nature of solids mixing and stratification in biofluidization as a result of biofilm formation, as was discussed in Sec. 5.3. 

Mass transfer considerations are critical in any bioprocess. In typical, aerobic, suspended cell fermentations, the major concern is the oxygen transfer rate, determined by the overall mass transfer coefficient, kft, and the driving force. In three-phase biofluidization, in which the cells are immobilized as a biofilm or within carrier particles, the situation is further complicated by possible intraparticle diffusion limitations. Numerous recent studies have addressed these issues. 

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