LAB metabolisms

During the fermentation process, LAB metabolism modifies the composition and the physico-chemical features of the foods, with acidification of the media being one of the most important changes. The lowering of pH impacts at different levels on BA formation it hampers the growth of contaminant microorganisms and modulates the activity of decarboxylases and proteolytic enzymes (Linares et al., 2012). 

Aside from potential sensory implications, acetic acid and associated products of LAB metabolism represent potent inhibitors to fermentatively growing Saccharomyces, delaying the onset of fermentation and potentially causing fermentation to stick (see previous discussion of Microbial Antagonism). At pH >3.5, bacterial carbohydrate metabolism (Peynaud and Domercq, 1968) or MLF (Giannakopoulis et al., 1984 Zeeman et al., 1982) yielded higher concentrations of acetic acid than parallel lots at a lower pH. 

LAB Metabolism in Light of Genomics, Comparative Genomics, and Metagenomics... 

Bergstrom, J. Hultman, E. (1967). A study of the glycogen metabolism during exercise in man. Scand. J. Clin. Lab. Invest. 19,218-228. 

The selective utilization of prebiotics by some, but not all, of the resident species alters the assemblages, densities and metabolic activities of the GIT bacteria. Of importance is the ability of prebiotics to increase the proportion of the resident bacteria represented by the lactic acid producing bacteria (LAB), resulting in changes of GIT and systemic functions (Swanson et al.. 

Heim K, 1 Schuphan, B Schmidt (1994) Behaviour of [ " C]-4-nitrophenol and [ " C]-3,4-dichloroaniline in lab sediment-water systems. 1. Metabolic fate and partitioning of radioactivity. Environ Toxicol Chem 13 879-888. 

Cross, C.E., Forte, T., Stocker, R., Louie, S., Yamamoto, Y., Ames, B.N. and Frei, B. (1990). Oxidative stress and abnormal cholesterol metabolism in patients with adult respiratory distress syndrome. J. Lab. Clin. Med. 115, 396-404. 

Battelle Pacific Northwest Labs. 1975. Effect of physico-chemical properties on metabolism of transuranium oxide aerosols inhaled by beagle dogs. Richland, WA Battelle Pacific Northwest Labs. BNWLSA5430. 

Meisel C, Roots I, Cascorbi I, Brink-mann U, Brockmoller J. How to manage individualized drug therapy application of pharmacogenetic knowledge of drug metabolism and transport. Clin Chem Lab Med 2000 38 869-876. 

Department of Pharmacokinetics, Pharmacodynamics, and Drug Metabolism, Pfizer Global Research and Development, Groton Labs, Groton, CT, USA... 

Consider one small molecule, phenylalanine. It is an essential amino acid in our diet and is important in protein synthesis (a component of protein), as well as a precursor to tyrosine and neurotransmitters. Phenylalanine is one of several amino acids that are measured in a variety of clinical methods, which include immunoassay, fluorometry, high performance liquid chromatography (HPLC see Section 4.1.2) and most recently MS/MS (see Chapter 3). Historically, screening labs utilized immunoassays or fluorimetric analysis. Diagnostic metabolic labs used the amino acid analyzer, which was a form of HPLC. Most recently, the tandem mass spectrometer has been used extensively in screening labs to analyze amino acids or in diagnostic labs as a universal detector for GC and LC techniques. Why did MS/MS replace older technological systems The answer to this question lies in the power of mass spectrometer. 

With one analysis, a few dozen diseases can be tested and, with less than 2 minutes a test, many hundreds of samples per day per instrument can be tested. This technique has been validated manyfold by its use in numerous screening and metabolic labs and is testimony to its power. Many new assays are being developed that follow a similar approach. 

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