Amino acids alcoholic fermentation

H2N-CH2 [CH2j3.CH(NH2) COOH. Colourless needles, m.p. 224 C (decomp.), very soluble in water, insoluble in alcohol. L-(-H)-Lysine is one of the basic amino-acids occurring in particularly large quantities in the protamine and histone classes of proteins. It is an essential amino-acid, which cannot be synthesized by the body and must be present in the food for proper growth. It can be manufactured by various fermentation processes or by synthesis. 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

The elucidation of the genetics and regulations of the Ehrlich pathway leading from amino acids to alcohols and the corresponding acids and esters—a pivotal metabolic route to flavours generated by traditional food fermentation processes—has attracted much research interest in the past. More recent inves-... 

The next step of the biotechnical sequence, yeast fermentation, is of the utmost importance to the chemistry of winemaking as well as to the formation of flavor substances. We have investigated this previously using 14C-tagged compounds (16). Amino acids, for example, enter the yeast fermentation with a quasi biochemical valence with regard to the formation of metabolic side products like alcohols and esters. In that respect, the composition of the fermentation substrate, the grape must, is highly important to the formation of aroma substances by yeasts. 

Deamination 17 Examples of deamination and decarboxylation include conversion of amino acids to fusel oil (leucine to isoamyl alcohol, isoleucine to amyl alcohol, and phenylalanine to phenyl ethanol). Fusel oil formation is a normal function of all yeast fermentations (in alcoholic beverages, levels range from trace to 2200 parts per million). Deamination Glutamic acid to gamma-OH-butyric acid (S. cerevisiae). 

Many useful compounds such as amino acids, nucleic acids, alcohols, vitamins, antibiotics, foods, etc. are produced in fermentation industries. Furthermore, many organic and inorganic compounds are present in waste waters. The determination of these compounds is required for control of fermentation and environment. Analysis of these compounds can be done by spectrophotometric methods. However, complicated procedures and long reaction times are required. 

Biogenic amines in wine and fermented foods are formed primarily via the microbial decarboxylation of amino acids. Examples, such as histamine, tyramine, and phenylethylamine are toxic, especially in alcoholic beverages. Ethanol can inhibit the monoamino oxidase responsible for amine detoxification (Maynard and Schenker, 1996). Histamine can induce allergenic reactions in humans, such as rashes, edema, headaches, hypotension. Tyramine and phenylethylamine can cause hypertension and other symptoms related to the release of noradrenaline. 

Together with proteins and peptides, amino acids constitute the main components of the nitrogenous fraction of musts and wines. They are also the most studied and best known nitrogenated components in wines. Free amino acids in musts are of paramount importance. They constitute a source of nitrogen for yeasts in alcoholic fermentation, for lactic acid bacteria in malolactic fermentation, and can also be a source of aromatic compounds (Kosir and Kidric, 2001). In certain cases, some amino acids... 

Solvent extraction has long been established as a basic unit operation for chemical separations. Chapter 7 summarizes the effects of temperature, pH, ion pairs, and solvent selection on solvent extraction for biomolecules. Solvent extraction of fermentation products such as alcohols, aliphatic carboxylic acids, amino acids, and antibiotics are discussed. Enhanced solvent extraction using reversed micelles and electrical fields are also discussed. Solvent-extraction equipment and operational considerations are adequately covered in this chapter. 

Since the discovery of fermentative activity of microorganisms in the eighteenth century and its proof by the French scientist Louis Pasteur, fermentative production of alcohols, amino acids, enzymes (biocatalysts), organic... 

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