Biosynthesis Butanol

From the discussion above is it clear that both AG and LAM play paramount roles in the infection and smvival of mycobacteria in the host. Drugs that act by inhibiting the biosynthesis of these polysaccharides are expected to show antimycobacterial action. One of the commonly used antimberculosis agents, ethambutol [(S,S )-2,2 -(ethylenediimino)di-l-butanol, 22] (Fig. 7), has been used for the treatment of tuberculosis since 1961, when it was first reported to have antimycobacterial activity... 

Examples of the use of induced biosynthetic effects for the deduction of the processes involved include the use of puromycin and cyclohexi-mide. These compounds, according to experiments with other systems, inhibit protein synthesis. Thus the inhibition of biosynthesis of hyaluronic acid and dermatan sulfate in human fibroblast cultures (M13, M16), of hyaluronic acid in synovial cells (S31), and of chondroitin sulfate (HI) led to the conclusion that the synthesis of protein acceptor is necessary for the polysaccharide chain initiation. Comparison of the effects of 1-butanol on the biosynthesis of chick cartilage chondroitin sulfate and streptococcal hyaluronic acid led to the suggestion that binding of Mg + ions and the uridine diphosphate moiety results in stabilization of the spatial arrangement of the specific enzymes (S47, T4). 

Saponins Isolated from Plants Grown in the Field. The crude saponins (Fig. 3) were isolated from each part of the plant. For all of the data report on TLC, HPLC, MS, and bioassay the saponins were processed through the first stage of purification, which was extracted with 1-butanol. Leaf biosynthesis of crude saponins (Fig. 3) occurred in 3 bursts at approximately 30-50, 55-65, and 75-90 days, which corresponded to the initiation of flowers, leaf development, and maturity. The total saponins accumulated corresponds to 1.8 g saponins/plant however, in the purification with 1-butanol about 40% of the crude saponins were lost leaving about 1 g saponins/plant being produced during the life cycle. The stems were relatively constant at around 20-30 mg saponins/plant after 30-40 days of age the roots were similar in content to the leaves in that at 30-40 days of age they increased from 20 mg/plant to 70-80 mg/plant which corresponded with the second and third trifoliate leaf development. This burst of biosynthetic activity of saponins coincides with the onset of fungal root disease which was identified earlier as due to Rhizoctonia spp, Pythium spp, and Fusarium spp (8,9, 15-17). 

Methyl-butanol (2MB) is synthesized via the isoleucine pathway (Figure 15.4), which is similar to the valine biosynthesis pathway. One of the challenges for 2MB production is that it passes over the same cassette of genes as in isobutanol production. A recent study [106] indicated that enhancing the citramalate pathway to direct the carbon flux from pyruvate to a-ketobutyrate led 2MB production to about 200 mg 1" with minimum side products such as 1-propanol and isobutanol. 

Lan, E.L, Ro, S.Y., and Liao, J.C. (2013) Oxygen-tolerant coenzyme A-acylating aldehyde dehydrogenase facilitates efficient photosynthetic n-butanol biosynthesis in cyanobacteria. Energy Environ, ScL, 6 (9), 2672 —2681. 

First attempts for the production of 1-butanol by S. cerevisiae relied on the introduction of enzymes from native producers to convert acetoacetyl-CoA into 1-butanol. Acetoacetyl-CoA is a natural metabolite of yeast, derived from acetyl-CoA, which itself is a central metabohte that serves as a key precursor in the biosynthesis of various biomolecules [8]. Another approach makes use of the endogenous Ehrhch pathway for isobutanol synthesis. Significant improvements in butanol production were finally reached, eliminating competitive pathways, and particularly taking care to maintain cofactor balance in producing strains [8]. 

Yu MR, Du YM, Jiang WY, Chang WL, Yang ST, Tang IC. (2012). Effectsof differentreplicons in conjugative plasmids on transformation efficiency, plasmid stability, gene expression and n-butanol biosynthesis in Clostridium tyrobutyricum. Appl Microbiol Biotechnol, 93, 881-889. 

Atsumi S, Liao JC. (2008). Directed evolution of Methanococcus jannaschii citramalate synthase for biosynthesis of 1-propanol and 1-butanol by Escherichia coli. Appl Environ Microbiol, 74,7802-7808. 

Figure 19.1 CoA-dependent n-butanol biosynthesis pathways in C acetobutylicum (ABE fermentation) and its variations. The non-native enzymes are marked with underscores for differentiation. Enzyme abbreviations Pfor, pyruvate ferredoxin oxireduc-tase HydA, hydrogenase Fnor, ferredoxin ...

Butanol has been synthesized in various organisms through different pathways. The CoA-dependent pathway from Clostridium and its variations (Figure 19.1) are the best studied [65]. This pathway is chemically similar to the reversal of P-oxidization [66, 67]. The intrinsic iteration nature of reverse p-oxidization also enables the biosynthesis of longer chain alcohols, for example, -hexanol and n-octonol [66]. The citramalate and threonine pathways fall into the same broad group as the keto-acid pathway (Figure 19.2), which is more commonly utihzed for isobutanol production. 

Gulevich, A., Skorokhodova, A., Sukhozhenko, A., Shakulov, R., and Debabov, V. (2012) Metabolic engineering of Escherichia coli for 1-butanol biosynthesis through the inverted aerobic fatty acid P-oxidation pathway. Biotechnol. Lett, 34, 463-469. 

In this way, by only using two nmi-native steps, the amino acid synthesis pathway was diverted towards alcohol generatiOTi. Additionally, unlike native butanol formation pathways in Clostridia, the amino acid biosynthesis pathways avoid the requirement of involving CoA-dependent intermediates (Shen and Liao... 

The relatively high-level isobutanol production using the amino acid pathway shows the potential of this strategy and small stepwise optimisation. This versatile approach was used for production of 1-butanol (Atsumi et al. 2008a) over the norvaline biosynthesis pathway, which is a minor side reaction of leucine biosynthesis (Connor and Liao 2009). 

As stated above, clostridial species use a coenzyme-A-dependent biosynthesis pathway to produce 1-butanol (Jones and Woods 1986 Atsumi et al. 2008b). On the... 

The biosynthesis of fhe solvent 1-butanol involved ABE fermentation by the strictly anaerobic microorganism Clostridium (Liitke-Eversloh et al., 2011). This ABE fermentation, known as the oldest industrial fermentation, was first invented by Pasteur in 1861... 

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