Lactic acid, biochemistry

The chemical engineering approach began with an analysis of the biochemistry of platelet metabolism. Like many cells, platelets consume glucose by two pathways, an oxidative pathway and an anaerobic pathway. The oxidative pathway produces carbon dioxide, which makes the solution containing the platelets more acidic (lower pH) and promotes anaerobic metabolism. This second metabolic pathway produces large amounts of lactic acid, further lowering pH. The drop in pH from both pathways kills the platelets. 

The contribution of these agents, individually or in various combinations, has been assessed in model cheese systems from which one or more of the agents was excluded or eliminated, e.g. by using an acidogen rather than starter for acidification or manufacturing cheese in a sterile environment to eliminate non-starter lactic acid bacteria (NSLAB). Such model systems have given very useful information on the biochemistry of ripening. 

Fermentation of lactic acid with Rhizopus arrhizus in a stirred tank reactor with a periodical bleed and feed operation. Process Biochemistry, 38, 1573. 

For a proper appreciation of the underlying biochemistry of dry skin we should consider this common condition as a dysfunction of one or more of the vital processes that generate and protect the water-holding capacity of the SC. With this concept in mind, in this chapter we will focus initially on the generation and critical importance of the NMF to SC function. Second, we will consider the effects of topically applied NMF components, and in particular the effects of lactic acid and its isomers, on the alleviation of dry skin symptoms. Finally, we will consider briefly the technologies that can influence NMF generation through stimulation of the synthesis of the NMF-precursor molecules. 

Wang CJ, Bajpai RK, and lannotti EL, Nondispersive extraction for recovering lactic acid. Applied Biochemistry and Biotechnology 1991, 589-603. 

Altaf, M., Naveena, B.J., Venkateshwar, M., Kumar, E.V., and Reddy, G. 2006. Single step fermentation of starch to 1(+) lactic acid by Lactobacillus amylophi-lus GV6 in SSF using inexpensive nitrogen sources to replace peptone and yeast extract—Optimization by RSM. Proceedings in Biochemistry 41 465-472. 

Chen, R. and Lee, Y.Y. 1997. Membrane-mediated extractive fermentation for lactic acid production from cellulosic biomass. Applied Biochemistry and Biotechnology 63 435-448. 

FIGURE 3.2 Anaerobic conversion of pymvic acid or pyruvate to lactic acid or lactate with enzyme and supportive reaction shown. (Based on information in Voet and Voet, Biochemistry, p. 464 Harris, in Textbook of Biochemistry, p. 334.)... 

Kok J, Holo H, van Belkum MJ, Haandrikman AJ, Nes IF (1993) Non-nisin bacteriocins in lactococci biochemistry, genetics and mode of action. In Hoover D, Steenson L (eds) Bacteriocins of Lactic Acid Bacteria. Academic Press, New York, pp 121-150... 

The biochemistry of the lactic acid bacteria has received attention [4, 17-20]. Homofermentative strains such as the Pediococci use the glycolytic pathway for the dissimilation of carbohydrates, such as glucose, to yield pyruvic acid. Pyruvic acid acts as a hydrogen acceptor and is converted to lactic acid by means of an NADH-dependent lactic dehydrogenase. It is believed that the homofermentative strains use in addition the hexose monophosphate pathway and possibly a phosphoketolase pathway (Fig. 21.2) when pentoses are degraded. The heterofermentative strains on the other hand lack both aldolase and hexose isomerase, essential for the operation of the glycolytic pathway, while pyruvic acid will not readily function as a... 

Tsai, J. S., Lin, Y. S., Pan, B. S., Chen, T. J. (2006). Antihypertensive peptides and y-aminobutyric acid from prozyme 6 facilitated lactic acid bacteria fermentation of soymiUc. Process Biochemistry, 41, 1282-1288. 

Botes, A., Todorov, S. D., von Mollendorff, J. W., Botha, A., Dicks, L. M. T. (2006). Identification of lactic acid bacteria and yeast from boza. Process Biochemistry, 42, 267-270. 

The uniformity in this biochemistry is in sharp contrast with the degrees of freedom one has in choosing the microbes, the acid-neutralizing agent, nutrients, and carbohydrates needed for industrial lactic acid fermentation. Only delicate weighing of the pros and cons of every possibility leads to an economically feasible fermentation. 

D-Lactide can be obtained if one has the appropriate biochemistry to produce the D-enantiomer of lactic acid by fermentation of carbohydrates. Copolymeiization of controlled mixtures of l- and D-lactides subsequently offers the advantage of precise control over PLA properties. Moreover, D-lactide is the monomer for the production of poly(D-lac-tide), which is able to form high-melting stereocomplex PLA via 1 1 racemic cocrystallization with P(L)LA, as will be discussed in Chapter 5 [89]. 

With such thoughts in mind, I have tried my hand at a little history of biochemistry and have chosen lactic acid as a theme. Ochoa himself has contributed much to this subject. Some of his early work was on enzymatic lactate formation in heart muscle and brain and on the role of DPN and diphosphothiamin as coenzymes, all published between 1937 and 1942. 

Taroncher-Oldenburg G, Nishia K, Stephanopoulos G (2000) Identification and analysis of polyhydroxyalkanoate-specific P-ketothiola e and acetoacetyl coenzyme A reductase genes in cyanobacterium Synechocystis p. strain PCC6803. Appl Environ Microbiol 66 4440-4448 Thauer RK (1989) Biochemistry of acetic acid metabolism in anaerobic chemotropic bacteria. Ann Rev Microbiol 43 43-67 Toda K, Park YS, Asakura T, Cheng CY, Ohtake H (1989) High rate acetic acid production in a shallow flow bioreactor. Appl Microbiol Biotechnol 30 559-563 Tsai SP, Moon S-H (1998) An integrated bioconversion process for the production of L-lactic acid from starchy potato feed stocks. Appl Biochem Biotechnol 70-72 417-428... 

Poolman B, Kunji E, Hagting A, Juillard V, Konings W (1995) The proteolytic pathway of Lactococcus lactis. J Appl Bacteriol 79 65S-75S Pritchard GG, Coolbear T (1993) The physiology and biochemistry of the proteolytic system in lactic acid bacteria. FEMS Microbiol Rev 12 179-206 Rafter JJ (1995) The role oflactic acid bacteria in colon cancer prevention. Scand J Gastroenterol 30 497-502... 

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