Fermentative syntheses requirements

Specifications. The specifications for ethyl alcohol are designed with sufficient latitude to allow for the two principal means of production, synthesis from ethylene and fermentation. The requirements given by the U.S. Pharmacopeia (USP) and the American Chemical Society (ACS) generally form the foundation for the most widely used specifications (255,256). A tabulation of the specifications from the major alcohol producers, with consideration for the USP and ACS requirements, is shown in Table 5. 

All the micro-organisms working in fermentation processes require the fundamental building blocks for their synthesis a source of carbon, a source of nitrogen, salts and co-factors. 

In this process, sugars, obtained from biomass, are fermented at low pH into cis-muconic acid. The process of microbial muconic adic formation was already described by Frost and coworkers, who developed E. coli WNl/pWN2.248 that synthesized 36.8 g/L of c/s,ci>muconic acid in 22% (mol/mol) yield from glucose after 48 h of culturing under fed-batch fermentation conditions [147]. This strain did not possess the aroE encoded shikamate dehydrogenase preventing the cells to convert 3-dehydroshikimic acid into shikimic acid which is available for production of cis,cis-muconic acid. Optimization of microbial cis.m-muconic acid synthesis required expression of three enzymes not typically found in E. coli. A recent patent application by Bui et al. describes a productivity of 59 g/L cis muconic acid from 248 g/L glucose by a modified E. coli. in a 20 L fermenter in 88 h. 

Since (A) does not contain any other functional group in addition to the formyl group, one may predict that suitable reaction conditions could be found for all conversions into (A). Many other alternative target molecules can, of course, be formulated. The reduction of (H), for example, may require introduction of a protecting group, e.g. acetal formation. The industrial synthesis of (A) is based upon the oxidation of (E) since 3-methylbutanol (isoamyl alcohol) is a cheap distillation product from alcoholic fermentation ( fusel oils ). The second step of our simple antithetic analysis — systematic disconnection — will now be exemplified with all target molecules of the scheme above. For the sake of brevity we shall omit the syn-thons and indicate only the reagents and reaction conditions. 

A fermentation route to 1-butanol based on carbon monoxide employing the anaerobic bacterium, Butyribacterium methjlotrophicum has been reported (14,15). In contrast to other commercial catalytic processes for converting synthesis gas to alcohols, the new process is insensitive to sulfur contaminants. Current productivities to butanol are 1 g/L, about 10% of that required for commercial viabiUty. Researchers hope to learn enough about the bacteria s control mechanisms to be able to use recombinant DNA to make the cells produce more butanol. 

Biotransformations are carried out by either whole cells (microbial, plant, or animal) or by isolated enzymes. Both methods have advantages and disadvantages. In general, multistep transformations, such as hydroxylations of steroids, or the synthesis of amino acids, riboflavin, vitamins, and alkaloids that require the presence of several enzymes and cofactors are carried out by whole cells. Simple one- or two-step transformations, on the other hand, are usually carried out by isolated enzymes. Compared to fermentations, enzymatic reactions have a number of advantages including simple instmmentation reduced side reactions, easy control, and product isolation. 

The first direct approach requires a long stand of the reaction mixture under high temperature. In the crystal form the product could be receive only after the fermentative splitting of un-reacted glucose. In the further studies [4-6] the direct method was somewhere improved and applied to other mono- and disaccharides, however, there were no principal changes in the synthesis methods. 

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