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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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14.4.1 Organic solvents in microbial production 859<br />

some solutions have been already found in this area, further progress is expected in the near<br />

future. A key problem is the selection <strong>of</strong> useful solvents in combination with a suitable microbe.<br />

Many solvents may be considered with their specific process properties, and many<br />

microorganisms may be considered also with their specific advantages or disadvantages.<br />

Only on the basis <strong>of</strong> a detailed understanding <strong>of</strong> the functioning <strong>of</strong> a microbial cell in the<br />

presence <strong>of</strong> solvents will it be possible to make a rational selection for a good combination<br />

solvent/organism. In the following section we will discuss these key questions. We will also<br />

describe recently found solvent-tolerant bacteria and will provide some examples <strong>of</strong><br />

biotransformation using solvent-tolerant bacteria.<br />

14.4.1.2 Toxicity <strong>of</strong> organic solvents<br />

The toxicity <strong>of</strong> an organic solvent is closely related to its hydrophobicity, as expressed by<br />

the log PO/W values, 12-16 the logarithm <strong>of</strong> the partition coefficient <strong>of</strong> the solvent between<br />

1-octanol and water (Table 14.4.1). In general, the Gram-negative bacteria show relatively<br />

higher solvent tolerances than the Gram-positive bacteria. 12,14 This may be caused by the<br />

difference in the composition <strong>of</strong> the cell envelope. <strong>Solvents</strong> with a high log PO/W resulted in<br />

the highest activities, but the range <strong>of</strong> log PO/W tolerated by an organism is dependent on the<br />

type <strong>of</strong> microorganism. In the following section we will describe what happens in the cell in<br />

the presence <strong>of</strong> solvents.<br />

Table 14.4.1. Relationship between the growth <strong>of</strong> a cell exposed to an organic solvent<br />

and the value <strong>of</strong> log P O/W <strong>of</strong> the solvent. [After reference 14]<br />

Solvent<br />

log P O/W<br />

Pseudomonas putida<br />

IH-2000<br />

Pseudomonas putida<br />

IFO3738<br />

Pseudomonas<br />

fluorescens IFO3507<br />

Escherichia coli IFO3806<br />

Achromobacter<br />

delicatulus LAM1433<br />

Alcaligenes faecalis<br />

JCM1474<br />

Agrobacterium<br />

tumefaciens IFO3058<br />

dodecane 7.0 + + + + + + + + +<br />

decane 6.0 + + + + + + + + -<br />

nonane 5.5 + + + + + + + + -<br />

n-hexyl ether 5.1 + + + + + + + + -<br />

octane 4.9 + + + + + + + + -<br />

isooctane 4.8 + + + + + + + - -<br />

cyclooctane 4.5 + + + + + + - - -<br />

diphenyl ether 4.2 + + + + + - - - -<br />

n-hexane 3.9 + + + + + - - - -<br />

propylbenzene 3.7 + + + + - - - - -<br />

o-dichlorobenzene 3.5 + + + - - - - - -<br />

cyclohexane 3.4 + + + - - - - - -<br />

ethylbenzene 3.2 + + - - - - - - -<br />

Bacillus subtilis<br />

AHU1219<br />

Saccharomyces uvarum<br />

ATCC26602

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