Yeast lactone production

For example, the two carbonyl groups in methyl l-methyl-2,5-dioxocyclopentane acetate are enantiotopic and the two faces of each carbonyl group are diastereotopic. Yeast reduction furnished 1 (albeit in low chemical yield), by attack of the pro-R carbonyl group from its sterically less hindered Re-face. The immediate lactone formation indicates the relative configuration at the two stereogenic centers, while the absolute configuration of the yeast reduction product had to be determined (see p 437)133. 

The closely related 5-decanolide (5-decalactone), not only found in many fruits but also found in dairy products, exhibits a creamy-coconut, peach-like aroma [49] and can be synthesised from the corresponding a,(3-unsaturated lactone 2-decen-5-olide found in concentrations of up to 80% in Massoi bark oil using basidiomycetes or baker s yeast [229]. After about 16 h of fermentation, 1.2 g 5-decanolide was obtained. At the same time, the minor lactone in... 

Reduction of 2,2-dimethyl-cyclohexane-1,3-dione (50) with Baker s yeast gave alcohol (ee 98.3%) whose tetrahydropyranyl derivative on methoxycarbonylation produced (51) quantitatively. Michael addition of (51) with methyl vinyl ketone followed by heating the adduct under reflux with pyrrolidine in benzene yielded (52) in 85% yield as stereoisomeric mixture whose separation presented problems. In order to eliminate the complexity due to a chiral center in tetrahydropyranyl protective group, deprotection of (52) was achieved by treatment with p-toluenesulphonic acid in methanol. The product obtained was a mixture of the lactone (53) and hydroxy ester (54). Probably the stereoisomer of... 

Lactone. Various fungi, including Bakers yeast and Geotrichum candi-dum, have been shown to produce optically active lactones, useful chiral synthon, via the stereoselective reduction of suitable unsaturated precursors (42). Figure 15 shows the production scheme for a chiral, substituted diketone, a synthon for optically active carotenoids. 

Other aldehydes/alcohols can be produced following the same principles. For production of Cio-lactone, however, a different strategy has to be followed after the formation of the hydroperoxide. It involves the fermentative -oxidation of the hydroperoxide intermediate by the yeast Pichia etchellsii, and the subsequent cyclization of 5-hydroxydecanoic add to the corresponding S(-)-8-decalactone. TTae routes to (Z3)-hexenol and S(-)-6-decalactone are depicted in Fig. 7.11. 

Traditional fermentation using microbial activity is commonly used for the production of nonvolatile flavor compounds such as acidulants, amino acids, and nucleotides. The formation of volatile flavor compounds via microbial fermentation on an industrial scale is still in its infancy. Although more than 100 aroma compounds may be generated microbially, only a few of them are produced on an industrial scale. The reason is probably due to the transformation efficiency, cost of the processes used, and our ignorance to their biosynthetic pathways. Nevertheless, the exploitation of microbial production of food flavors has proved to be successful in some cases. For example, the production of y-decalactone by microbial biosynthetic pathways lead to a price decrease from 20,000/kg to l,200/kg U.S. Generally, the production of lactone could be performed from a precursor of hydroxy fatty acids, followed by p-oxidation from yeast bioconversion (Benedetti et al., 2001). Most of the hydroxy fatty acids are found in very small amounts in natural sources, and the only inexpensive natural precursor is ricinoleic acid, the major fatty acid of castor oil. Due to the few natural sources of these fatty acid precursors, the most common processes have been developed from fatty acids by microbial biotransformation (Hou, 1995). Another way to obtain hydroxy fatty acid is from the action of LOX. However, there has been only limited research on using LOX to produce lactone (Gill and Valivety, 1997). 

Similar to the reduction of 3-oxo acids, 4- and 5-oxo acids and Iheir corresponding esters are reduced by baker s yeast to the (/ -configurated alcohols, often in high enantiomeric excess. In general, the reduced products are isolated as the corresponding y- and d-lactones (Table 6) which have an alkyl substituent of 2 to 13 carbon atoms in length171,172,174. 

In another paper by Albrecht et aL, [48] the biosynthetic pathway involved in the production of aliphatic lactones was studied. In particular, the study was focused on the mechanism of the biotransformation of Sy and (7 yS)-13-hydroxy-(Z,A)-9,ll-octadecadienoic acid into the optically pure (/ )- -decalactone by the yeast Sporobolomyces odorus. For this purpose, deuterium-containing derivatives of coriolic acid needed to be synthesized. Figure 10 shows the synthetic approach chosen by the authors to produce 13-HSA-13-J and 13-HSA-9,10,11,12- 4 starting from linoleic acid. 

Since fatty acid and aromatic synthetases have many properties in common, it is interesting to consider the effect of omitting NADPH from incubations catalyzed by these enzymes and to examine the consequences. In all cases studied from animal (Bressler and Wakil, 1%2 Nixon et al., 1%8), yeast (Yalpani et al., 1969), and bacterial origin (Brock and Bloch, 1966), fatty acid synthesis is naturally abolished, but a Q compound, triacetic acid lactone (4-hydroxy-6-methyl-2-pyrone) (VII), is formed instead. This product is also made when the NADPH-requiring 6-methylsalicylate synthetase is deprived of this nucleotide (Dimroth et al., 1972), but the relative rate of synthesis is considerably greater than that produced by fatty acid synthetase in P. patulum (Yalpani et al., 1%9). However, Scott et al. (1971) have reported that triacetic acid lactone is also formed by 6-methylsalicylate synthetase, albeit at a reduced rate, even in the presence of NADPH. 

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