Solvent tolerance

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

Kieboom, J, JJ Dennis, JAM de Bont, GJ Zylstra (1998) Identification and molecular characterization of an efflux pump involved in Pseudomonas putida S12 solvent tolerance. J Biol Chem 273 85-91. 

Li X-Z, L Zhang, K Poole (1998) Role of multidrug efflux systems of Pseudomonas aeruginosa in organic solvent tolerance. J Bacterial 180 2987-2991. 

Pinkart HC, DC White (1997) Phospholipid biosynthesis and solvent tolerance in Pseudomonas putida strains. J Bacteriol 179 4219 226. 

Ramos JL, E Duque, J-J Rodrlguez-Herva, P Godoy, A Haidour, F Reyes, A Fernandez-Barrero (1997) Mechanisms for solvent tolerance in bacteria. J Biol Chem 272 3887-3890. 

Ramos-Gonzalez M-I, A Ben-Bassat, M-J Campos, JL Ramos (2003) Genetic engineering of a highly solvent-tolerant Pseudomonas putida strain for biotransformation of toluene to p-hydroxybenzoate. Appl Environ Microbiol 69 5120-5127. 

One of the main obstacles for whole-cell microbial transformation in an organic solvent is its biocompatibility, which has led to screening for organic-solvent-tolerant microorganisms. Numerous organic-solvent-tolerant microorganisms have been found and their tolerance mechanisms have been reviewed [14,33,34]. Two-phase biotransformation systems have been successfully implemented for the production of pharmaceutically relevant metabolites. 

Heipieper, H.J., Neumann, G., Cornelissen, S. and Meinhardt, F. (2007) Solvent-tolerant bacteria for biotransformations in two-phase fermentation systems. Applied Microbiology and Biotechnology, 74, 961-973. 

Sardessai, Y.N. and Bhosle, S. (2004) Industrial potential of organic solvent tolerant bacteria. Biotechnology... 

In addition to desulfurization activity, several other parameters are important in selecting the right biocatalyst for a commercial BDS application. These include solvent tolerance, substrate specificity, complete conversion to a desulfurized product (as opposed to initial consumption/removal of a sulfur substrate), catalyst stability, biosurfactant production, cell growth rate (for biocatalyst production), impact of final desulfurized oil product on separation, biocatalyst separation from oil phase (for recycle), and finally, ability to regenerate the biocatalyst. Very few studies have addressed these issues and their impact on a process in detail [155,160], even though these seem to be very important from a commercialization point of view. While parameters such as activity in solvent or oil phase and substrate specificity have been studied for biocatalysts, these have not been used as screening criteria for identifying better biocatalysts. 

Further work at EniTecnologies was conducted with Rhodococcus strains. Rhodococ-cus was selected for its metabolical versatility, easy availability in soils and water, and remarkable solvent tolerance. Its capabilities for catalyzing diverse transformation reactions of crude oils, such as sulfur removal, alkanes and aromatics oxidation and catabolism caught their attention. Hence, genetic tools for the engineering of Rhodococcus strains have been applied to improve its biotransformation performance and its tolerance to certain common contaminants of the crude oil, such as cadmium. The development of active biomolecules led to the isolation and characterization of plasmid vectors and promoters. Strains have been constructed in which the careful over-expression of selected components of the desulfurization pathway leads to the enhancement of the sulfur removal activity in model systems. Rhodococcus, Gordona, and Nocardia were transformed in this way trying to improve their catalytic performance in BDS. In a... 

Since the isolation of IGTS8, many other Rhodococcus as well as Mycobacterium strains capable of sulfur-specific desulfurization via the 4S pathway have been isolated. Genetic analysis of some of these strains has shown that the dsz genes are almost identical in all these strains however, the strains still differ in their rate of desulfurization. It has been realized that this is due to the difference in non-desulfurizing traits of the strains. These traits are mostly physiological differences between the strains. These parameters play a secondary role in determining the rate of desulfurization in these strains. These include the ability to emulsify the oil phase, solvent tolerance and resistance to various... 

Unfortunately, the low aqueous solubility of the DCL components precluded templating studies with the intended target microtubulin. As proof of principle, the proteins albumin and subtilisin were substituted as organic solvent tolerant alternatives. Starting from the homodimeric compounds 45 and 48, the amount of heterodimer 51 formed was shown to be influenced by the presence of the proteins. 

Immobilisation of microorganisms Two-phase bioprocess with an organic solvent as the precursor reservoir Resting cells instead of growing ones Precursor-tolerant (solvent-tolerant) strains Fungal spores instead of mycelia... 

Recently, organic solvent tolerant bacteria, a novel group of extremophilic microorganisms that combat these destructive effects and thrive in the presence of high concentrations of organic solvents as a result of various adaptations, are being explored for their potential in industrial and environmental biotechnology [29],... 

Chem. Soc., 126, 14411-14418 Skander, M., Malan, C., Ivanova, A. and Ward, TR. (2005) Chemical optimization of artificial metaUoenzymes based on the biotin-avidin technology (S)-selective and solvent-tolerant hydrogenation catalysts via the introduction of chiral amino acid spacers. Chem. Commun., 4815-4817 Ward, TR. (2005) Artificial metallo-enzymes for enantioselective catalysis based on the noncovalent incorporation of organometallic moieties in a host protein. Chem.-Eur. J., 11, 3798-3804 Letondor, C. and Ward, TR. (2006) Artificial metaUoenzymes for enantioselective catalysis Recent advances. Chem. Bio. Chem., 7, 1845-1852. 

Pinkart, H. C., J. W. Wolfram, R. Rogers, and D. C. White, Cell envelope changes in solvent-tolerant and solvent-sensitive Pseudomonasputida strains following exposure to o-xylene , Appl. Environ. Microbiol., 62, 1129-1132 (1996). 

Ramos, J. L., E. Duque, J.-J. Rodriguez-Herva, P. Godoy, A. Haidour, F. Reyes, and A. Fernandez-Barrero, Mechanisms for solvent tolerance in bacteria , J. Biol. Chem., 272, 3887-3890 (1997). 

The cross-sectional flow velocity through the resin columns was maintained at 10 cm/min. The columns were each rinsed with 2.5 bed volumes of 1 M HC1 followed by 2.5 bed volumes of distilled water to remove metallic oxides and other inorganic constituents. Finally, the organic components were eluted with 2.5 bed volumes of 95 ethanol. Ethanol was selected as the eluent because it seemed to be the best choice as a solvent tolerated by animals used in proposed biological tests. 

A fluoroelastomer manufactured by Du Pont called Kalrez, has mechanical properties and resistance to oxidants which are similar to those of Viton. In contrast with Viton, Kalrez has good resistance to polar molecules such as amines, ethers, ketones, and esters. Kalrez is unique among the elastomers in its tolerance to both polar and nonpolar solvents. The cost of O-rings made from Kalrez is very high, but for certain critical applications this cost can be justified because of the outstanding range of solvent tolerance. 

Finally, recombination has the advantage of allowing parallel processing in screening. Several screens could be processed simultaneously for searching a variety of different criteria. Mutations which provide enhanced activity could be examined in one screen, while other screens could examine improvements in stability, solvent tolerance, expression levels or other properties. Positives could then be recombined to search for variants improved in several properties at... 

Feng J-Y, Liu J-Z, Ji L-N (2008) Thermostability, solvent tolerance, catalytic activity and conformation of cofactor modified horseradish peroxidases. Biochimie 90 1337-1346... 

Immobilized HRP on poly(ethylene matrix, the enzyme showed enhanced conformational and thermal stabilities, and higher solvent tolerance The temperature profile of the free HRP and [76]... 

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