Lactic acid conversion

The reasons for the confusion surrounding the mechanism of the malo-lactic fermentation are now apparent. In the malate system from Lactobaccillus plantarum, Korkes et al. (14) demonstrated carbon dioxide and lactic acid production from malic acid, but they were unable to show a large amount of pyruvic acid production. However, the cofactor requirement for the system indicated the need for an intermediate between malic acid and lactic acid, and pyruvic acid was the logical choice. At this time, the occurrence of enzymes requiring NAD in a function other than reduction-oxidation was not realized, so it was logical to conclude that the malic acid to lactic acid conversion involved a redox reaction. The later information, however, indicates that this is probably not the case. 

Yoghurt formation from milk by lactose to lactic acid conversion Lactobacillus... 

Ethyl acetate is the most likely ester to form, because of the relatively higher concentrations of ethanol and acetic acid than other ester forming constituents present. It is also the most important for the progress of maturation. Malic to lactic acid conversion is also an important part of the aging process, particularly for red wines (Eq. 16.14). 

Fig. 3 Atom economy vs F C for lactic acid conversion routes...

Tam MS, Craciun R, MIUct DJ, Jackson JE (1998) Reactirm and kinetic studies of lactic acid conversion over alkali-metal salts. Ind Eng Chem Res 37(6) 2360-2366... 

Moldes AB, Bustos G,Torrado A, Dominguez JM. Comparison between different hydrolysis processes of vine-trimming waste to obtain hemiceUulosic sugars for further lactic acid conversion. Appl Biochem Biotechnol 2007 143 244-56. 

Oxidation of lactic acid (conversion into pyruvate) Formation of additional acetic acid, carbon dioxide, and acetoin... 

Another reactive separation processes studied is the reactive distillation (see Figure 20.4.6). This concept is based on an integration of an esterification reactor and a reactive distillation column in the same unit. Gao et studied the effect of several operation parameters on ethyl lactate yield flow rate of feed lactic acid, ethanol/ lactic acid ratio and the effect of different feed points through the column. At studied conditions, only 52% of ethyl lactate yield was achieved. On the other hand, Asthana et al. using concentrated lactic acid solutions (88 wt%), achieved a lactic acid conversion of 93% and an ethyl lactate yield of 70%, with an ethyl lactate purity of 71% (mol%), avoiding the presence of water in the column bottom stream. 

The catalyst used (Amberlyst 15 - wet resin) acted also as water-absorbing resin. Experimental results were well predicted by a mathematical model developed by the authors, leading to an ethyl lactate productivity value of 31.7 kggL/Lresin day, 95% of purity and a lactic acid conversion of 100%, under optimal conditions. 

Wadley, D.C., Tam, M.S., Kokitkar, P.B., et al., 1997. Lactic acid conversion to 2,3-pentanedione and acrylic add over silica-supported sodium nitrate reaction optimization and identification of sodium lactate as the active catalyst. 

In the first step, propylene is introduced at 10—40°C into nitric acid, the concentration of which is kept at 50—75 wt % and molar ratio to propylene at 0.01—0.5, and converted into a-nitratolactic acid and lactic acid. a-Nitratolactic acid is oxidized by oxygen in the second step in the presence of a catalyst at 45—100°C to produce oxahc acid dihydrate. The overall yield based on propylene is greater than 90% and the conversion of propylene, 77.5%. The outhne of the process is shown in Figure 2. The RhcJ)ne-Poulenc process can be characterized by the coproduction of lactic acid. 

For some years, this type of vehicle was used in anionic electro deposition primers. However for automobiles cationic electro deposition primers are now preferred. The vehicles for cationic primers are proprietary but probably consist of the reaction product of epoxy resins and polyfunctional amines solubilized by the conversion of amine groups into salts using an acid such as lactic acid (2-hydroxypropanoic acid) [50-21-5] Alcohol-blocked... 

Glycolysis Metabolic pathway involving the conversion of glucose to lactic acid or ethanol. 

Phenyl-ethyl alcohol can be prepared by numerous methods, several of which are the subject-matter of patents. It may be prepared, for example, by the conversion of phenyl-bromo-lactic acid into phenyl-acetaldehyde, and then reducing this body with sodium. Or it may be prepared by reducing phenyl-acetic esters with sodium and absolute alcohol in the folio-wing manner —... 

Conversion at the chiral center if the mechanism is known. Thus, the Sn2 mechanism proceeds with inversion of configuration at an asymmetric carbon (see p. 390) It was by a series of such transformations that lactic acid was related to alanine ... 

Catalyst Glyceraldehyde Conversion Lactic Acid Yield Pyruvaldehyde Yield 1,3-Dihydroxyacetone Yield Other... 

As a model esterification reaction, the formation of ethyl lactate has been studied and its complete kinetic and thermodynamic analysis has been performed. The formation rate of ethyl lactate has been examined as a function of temperature and catalyst loading. In early experiments, it was determined that lactic acid itself catalyzes esterification, so that there is significant conversion even without ion exchange resin present. The Arrhenius plot for both resin-catalyzed and uncatalyzed reactions indicates that the uncatalyzed... 

Therefore, the overall kinetic rate expression for ethyl lactate conversion from lactic acid and ethanol can be given by ... 

The equilibrium conversion of lactic acid was measured by allowing reaction to proceed until no further changes were observed. We then used the data to calculate the equilibrium constant for the esterification reaction as a function of temperature. The final form of the equilibrium constant is given by the following equation. 

Fig. 7.4 Reaction scheme for the conversion of lactic acid to acrylic acid, propionic acid and...

A range of tetradentate Schiff-base ligands have also been employed to prepare discrete aluminum alkoxides. The most widely studied system is the unsubstituted parent system (256), which initiates the controlled ROP of rac-LA at 70 °C in toluene. The polymerization displays certain features characteristic of a living process (e.g., narrow Mw/M ), but is only well behaved to approximately 60-70% conversion thereafter transesterification causes the polydispersity to broaden.788 MALDI-TOF mass spectroscopy has been used to show that even at low conversions the polymer chains contain both even and odd numbers of lactic acid repeat units, implying that transesterification occurs in parallel with polymerization in this system.789... 

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