Fermentation and metabolism

Ribereau-Gayon, P, Glories, Y, Maujean, A., Dubourdieu, D. (2000c) Biochemistry of alcoholic fermentation and metabolic pathways of wine yeasts. In P. Ribereau-Gayon (Ed.), Handbook ofEnology, Vol 1, (pp. 51-74). Chichester John Wiley sons. Ltd. 

Five chapters are devoted to brewer s yeast and they consider, in appropriate detail, their taxonomy and related areas such as identification and characterization. Wort fermentation and metabolism are discussed and, in particular, the metabolic engineering of these organisms. The fact that brewer s yeast cultures are normally recycled through a number of wort fermentations is emphasized and details of yeast management between fermentations are discussed. 

Details fermentation and metabolic pathways to microbial fuels, chemical intermediates, chemical specialties, and biopolymers... 

Biochemistry of Alcoholic Fermentation and Metabolic Pathways of Wine Yeasts... 

Oku, T. Nakamura, S. (2002). Digestion, absorption, fermentation, and metabolism of functional sugar substitutes and their available energy. Pure and Applied Chemistry, 74, 1253-1261. 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

Except as an index of respiration, carbon dioxide is seldom considered in fermentations but plays important roles. Its participation in carbonate equilibria affects pH removal of carbon dioxide by photosynthesis can force the pH above 10 in dense, well-illuminated algal cultures. Several biochemical reactions involve carbon dioxide, so their kinetics and equilibrium concentrations are dependent on gas concentrations, and metabolic rates of associated reactions may also change. Attempts to increase oxygen transfer rates by elevating pressure to get more driving force sometimes encounter poor process performance that might oe attributed to excessive dissolved carbon dioxide. 

Nitrogen is normally supplied as an ammonium compound in dtric acid fermentations and suffident has to be supplied to enable the effect of manganese deficiency (increased levels of ammonium in the metabolic pool) to occur. Remember that increased metabolic pool ammonium has the effect of releasing the allosteric controls exerted on phosphofructokinase. 

The bacterial culture converts a portion of the supplied nutrient into vegetative cells, spores, crystalline protein toxin, soluble toxins, exoenzymes, and metabolic excretion products by the time of complete sporulation of the population. Although synchronous growth is not necessary, nearly simultaneous sporulation of the entire population is desired in order to obtain a uniform product. Depending on the manner of recovery of active material for the product, it will contain the insolubles including bacterial spores, crystals, cellular debris, and residual medium ingredients plus any soluble materials which may be carried with the fluid constituents. Diluents, vehicles, stickers, and chemical protectants, as the individual formulation procedure may dictate, are then added to the harvested fermentation products. The materials are used experimentally and commercially as dusts, wettable powders, and sprayable liquid formulations. Thus, a... 

Kluge C, A Tschech, G Fuchs (1990) Anaerobic metabolism of resorcylic acids (m-dihydroxybenzoates) and resorcinol (1,3-benzenediol) in a fermenting and in a denitrifying bacterium. Arch Microbiol 155 68-74. 

In this chapter, we will introduce an exciting class of natural product biosynthetic enzymes, the modular synthases, as well as their associated enzyme partners. We will discuss the use of metabolic engineering as a tool for small-molecule discovery and development, both through directed fermentation and combinatorial biosynthesis. In addition, we will review six classes of partner enzymes involved in the modification of polyketide (PK) and nonribosomal peptide (NRP) natural products. We believe that these enzymatic transformations hold great opportunities for synthetic chemists and will serve as the foundation for a new trend in both discovery and process chemistry. 

Tyramine is an amino acid which is present in large quantities in protein rich, fermented and stored products like some cheeses, sausages, red wines, beers etcetera. Tyramine is metabolized into nor-adrenaline by the enzyme mono-amino-oxidase (MAO). If MAO is inhibited by drags nor-adrenaline is accumulated and can give hypertensive crises. 

J. L. Galazzo and J. E. Bailey, Fermentation pathway kinetics and metabolic flux control in suspended and immobilized Saccharomyces cerevisiae. Enzyme Microb. Technol. 12(3), 162 172 (1990). 

Hydrogenase isoenzymes are also common among the metabolically more versatile bacteria (see Chapter 2). For instance, H2 metabolism and isoenzyme composition in enteric bacteria, including Escherichia coli and Salmonella typhimurium, appear to be differentially regulated under the two modes of anaerobic life, fermentation and anaerobic respiration (Table 3.1). Furthermore, biosynthesis of the individual isoenzymes appears to be controlled at a global level by the quality of the carbon source. 

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