Lactic acids isolation

Fig. 4.1 Chromatogram of (9-acetylated menthyl esters of organic acids separated on a WCOT glass capillary column (25 mxO.3 mm i.d.) coated with SP-1000, under isothermal conditions (temperatures in parentheses) (a) synthetic / 5-lactic acid (150°C) (b) synthetic / 5-glyceric acid (200°C) (c) / -lactic acid isolated from urine (150°C) and (d) / -glyceric acid isolated from urine (200°C). (Redrawn with modifications from Kamerling etal.y 1977)...

An example of a chiral compound is lactic acid. Two different forms of lactic acid that are mirror images of each other can be defined (Figure 2-69). These two different molecules are called enantiomers. They can be separated, isolated, and characterized experimentally. They are different chemical entities, and some of their properties arc different (c.g., their optical rotation),... 

Medium Boiling Esters. Esterificatioa of ethyl and propyl alcohols, ethylene glycol, and glycerol with various acids, eg, chloro- or bromoacetic, or pymvic, by the use of a third component such as bensene, toluene, hexane, cyclohexane, or carbon tetrachloride to remove the water produced is quite common. Bensene has been used as a co-solvent ia the preparatioa of methyl pymvate from pymvic acid (101). The preparatioa of ethyl lactate is described as an example of the general procedure (102). A mixture of 1 mol 80% lactic acid and 2.3 mol 95% ethyl alcohol is added to a volume of benzene equal to half that of the alcohol (ca 43 mL), and the resulting mixture is refluxed for several hours. When distilled, the overhead condensate separates iato layers. The lower layer is extracted to recover the benzene and alcohol, and the water is discarded. The upper layer is returned to the column for reflux. After all the water is removed from the reaction mixture, the excess of alcohol and benzene is removed by distillation, and the ester is fractionated to isolate the pure ester. 

Many carboxylic acids were first isolated from natural sources and were given names based on their origin. Fonnic acid (Latin formica, meaning ant ) was obtained by distilling ants. Since ancient times acetic acid (Latin acetum, for vinegar ) has been known to be present in wine that has turned sour. Butyric acid (Latin butyrum, meaning butter ) contributes to the odor of both rancid butter and ginkgo benies, and lactic acid (Latin lac, for milk ) has been isolated from sour milk. 

A mixture of 100 g of 5,5-dimethylacridan, 20 g of pulyerized sodium amide and 6.5 g of 1 -chloro-3-dimethylaminopropane in 50 ml of xylene is heated at reflux with stirring for one hour. To the cooled reaction mixture is added one yolume of water. The organic layer is separated and extracted several times with diluted lactic acid. The acidic extracts are combined, washed with ether and neutralized by alkali. The crude 10-(3 -dimethylaminopropvl)-5,5-dimethylacridan is isolated by ether extraction and purified by distillation in a high vacuum. The yield is 6,4 g BP 170°-1 B0°C/0.005 mm. n = 1.5990. 

The solution to this problem has been to isolate the lactide and to polymerize this directly using a tin(ii) 2-(ethyl)hexanoate catalyst at temperatures between 140 and 160 °C. By controlling the amounts of water and lactic acid in the polymerization reactor the molecular weight of the polymer can be controlled. Since lactic acid exists as d and L-optical isomers, three lactides are produced, d, l and meso (Scheme 6.11). The properties of the final polymer do not depend simply on the molecular weight but vary significantly with the optical ratios of the lactides used. In order to get specific polymers for medical use the crude lactide mix is extensively recrystallized, to remove the meso isomer leaving the required D, L mix. This recrystallization process results in considerable waste, with only a small fraction of the lactide produced being used in the final polymerization step. Hence PLA has been too costly to use as a commodity polymer. 

An alternative possibility is that of the biorefinery. In this concept a few key chemicals would be isolated from a small number of process steps. Whilst there are many possibilities for this, in one example the raw material, say com, could be cmshed to release oil (the first key product). The resulting mass could then be fermented to give several key platform chemicals such as ethanol, lactic acid and acetic acid. This attractive concept would be more viable if all the cellulose and lignin components could be efficiently used in the fermentation process. 

Wilderdyke, M.R., Smith, D.A. and Brashears, M.M. (2004) Isolation, identification, and selection of lactic acid bacteria from alfalfa sprouts for competitive inhibition of foodbome pathogens. Journal of Food Protection, 67, 947-951. 

Roushdi, M., Fahmy, A.A., and Mostafa, M. 1981a. Role of lactic acid in com steeping and its relation with starch isolation. Starch/Stdrke 33, 426-428. 

Glyoxalase, the glutathione-dependent enzyme which catalyzed the conversion of methyl glyoxal to lactic acid, was isolated by Neuberg and by Dakin and Dudley. 

Lonvaud-Funel, A. and Joyeux, A. (1994). Histamine production by wine lactic acid bacteria isolation of a histamine-producing strain of Leuconostoc oenos, J. Appl. Bacterial., 11, 401. 

Catalases catalyze the conversion of hydrogen peroxide to dioxygen and water. Two families of catalases are known, one having a heme cofactor and the second a structurally distinct family, found in thermophilic and lactic acid bacteria. The manganese enzymes contain a binuclear active site and the functional form of the enzyme cycles between the (Mn )2 and the (Mn )2 oxidation states. When isolated, the enzyme is in a mixture of oxidation states including the Mn /Mn superoxidized state and this form of the enzyme has been extensively studied using XAS, UV-visible, EPR, and ESEEM spectroscopies. Multifrequency EPR and microwave polarization studies of the (Mn )2 catalytically active enzyme from L. plantarum have also been reported. ... 

Bacterial strains were isolated that could grow on R-CPA [(R)-2-chloropropanoic acid], but not on S-CPA, because although both isomers were dehalogenated by different R and S specific dehalogenase isozymes, the -lactic acid formed from the S-CPA could not be metabolised. 

Isolation of product from the lactic acid occurs by solvent extraction. 

In the case of lactic acid and trimethylacetaldehyde the crude product is a ca. 4 1 mixture of the cis- and the trans-isomers, 4 and 5 (R = /-Bu). respectively75,77 from which pure 4 can be isolated with d.r. 98 2 after one recrystallization at — 78 °C11. Similarly, with 2-/er/-butyl-5-phenyl-1,3-dioxolan-4-one (1, Rl = C6H5 Rz = f-Bu) the crude product is already formed with a d.r. >99 1 75 77 in favor of the m-isomer, giving the pure cw-compound after recrystallization77,79. 

From the base-catalyzed degradation of D-fructose (pH 8.0), Shaw and coworkers147 identified 18 compounds, none of which was (a) isomeric with the starting material, or (b) a simple dehydration product. Among the products, the hydroxy-2-butanones and 1-hydroxy-2-propanone (acetol) were shown to participate in forming the carbo-cyclic products identified, but the mechanism of their formation was not elucidated. Several furan derivatives were isolated, but no lactic acid was isolated. In a similar study but with weak acid,41 most of the products were formed by a combination of enolization and dehydration steps, with little fragmentation. 

The o-carboxy anhydride of (d,l) lactic acid (4.0 mmol) was dissolved in 1.7 ml CH2CI2 and then treated with 4-dimethylamine pyridine (0.018 mmol) at an [anhydride]/[amine] ratio of 220. The mixture was reacted for 30 minutes at 25 °C and then concentrated. The product was isolated in 98% yield having an Mn of 30,400 Da with a polydispersity of 1.18. Duplicate and triplicate polymerizations were also performed and M s and polydispersities were found to be 30,300 and 34,900 Da with polydispersities of 1.18 and 1.13, respectively. 

Lactic acid bacteria isolated from wine may use residual sugars or alcohol, or decompose organic acids as a source of carbon for growth and energy. Malic, citric, and tartaric acids may be metabolized, depending on conditions. 

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