Strain, solvent-tolerant

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

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. 

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... 

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... 

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). 

Usami, R., Fukushima, T., Mizuki, T., Yoshida, Y., Inoue, A., Horikoshi, K. (2005). Organic solvent tolerance of halophilic archae, Haloarcula strains Effect of NaCl concentration on the tolerance and polar lipid composition. Journal of Bioscience and Bioengineering 99 169-174. 

The optimal pH of isomerases is 7-8. The cis-trans isomerase in the solvent-tolerant bacterium Pseudomonas putida S12 mainly works for the transformation of palmitoleic acid (9-ds-C16 l) to its geometrical isomer 9-trans-C16 l. For example, in case of the addition of 3-nitrotoluene, it gives a final cis/trans ratio of 32 68 [25], The cis-trans isomerase isolated from Pseudomonas sp. strain E-3 is flexible enough to convert the double bonds at positions 9,10, or 11, but not those at positions 6 or 7, of ds-monounsaturated fatty acids having a chain length of 14, 15, 16, or 17 carbon atoms. CTI is 400- to 450-fold more efficient than the reverse reaction [22], and occurs on fatty acids in the free form. However, in the presence of... 

Noar, J, Makwana, S.T., and Bruno-Barcena, J.M. (2014) Complete genome sequence of solvent-tolerant Clostridium beijerinckii strain SA-1. 

Organic solvents cause a shift in the ratio of saturated to unsaturated fatty acids. " In a solvent-tolerant strain, an increase in the saturation degree has been observed during adaptation to the presence of toluene. Solvent-tolerant strains also have the ability to synthesize tran -unsaturated fatty acids from the m-form in response to the presence of organic sol-vents. Increases in the saturation degree and the ratio of trans-(orm change the fluidity of the membrane and the swelling effects caused by solvents are depressed. 

The metabolism of organic solvents in solvent-tolerant strains contributes to solvent tolerance by degradation of the toxic compounds. This contribution, however, is considered to be limited because many solvent-tolerant strains show non-specific tolerance against various organic compounds. 

Speelmans et al. reported on the bioconversion of limonene to perillic acid by a solvent-tolerant Pseudomonas putida. The microbial toxicity of limonene is known to be very high. It is a major component of citrus essential oil and is a cheap and readily available base material. By using a solvent-tolerant strain perillic acid was obtained at a high concentration. This finding brings commercial production nearer. 

The applications of solvent-tolerant strains in microbial production processes are at present limited, but two strategic options are currently available to use such bacteria. Relevant genes can be introduced into solvent-tolerant organisms in order to produce the required product. This approach has been followed successfully by J. Wery in our laboratory who employed an 1-octanol-aqueous system. Methylcatechol was produced from toluene by solvent tolerant P. putida S12. Alternatively, the efflux pump can be expressed in a suitable solvent-sensitive host which would then be more tolerant for a particular solvent. 

Other benefits may arrive from solvent-resistant bacteria. Ogino et al. isolated Pseudomonas aeruginosa LST-03 whieh ean grow in organic solvents with logPo/w >2.4 and secrets organic solvent-stable lipolytic enzymes. They were able to purify an organic solvent-stable protease which was more stable than the commercially available proteases. Hence, solvent-tolerant strains have become a source for new enzymes. 

In the near future, the use of solvent-tolerant strains will make the application of organic solvents in biotransformations by whole cells a more realistic option. 

It is obvious that solvent tolerance is caused by a combination of the mechanisms described above. Figure 14.4.1.4 shows a schematic picture of toluene penetration and efflux in the solvent tolerant strain P. putida S12. Toluene enters the cell through the outer membrane. At present, it is unclear whether toluene passes through porins or through the phospholipid part of the cell. The efflux piunp recognizes and interacts with toluene in the cytoplasmic membrane. Toluene is then pxunped into the extracellular medium. 

One of the earliest applications of omics analysis to ethanol production was the use of DNA arrays to compare transcript abundance in E. coli KOll and its evolved derivative LYOl, which has improved ethanol tolerance and production relative to KOll [146]. This comparison showed that several pathways involved in the production of osmoprotectants, such as glycine and betaine, had increased expression in the evolved strain. Provision of these osmoprotectants to the parent strain improved growth in the presence of ethanol [146] and ethanol production [147]. This finding inspired later engineering efforts to improve organic solvent tolerance in E. coli [148]. 

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