Production of L Amino Acids

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CHM 3730 Production of L-amino acids. Student ID - 10254792 - Kelly Debono α-amino acids are important biological molecules, they are the building blocks of proteins and the 20 L-amino acids are ubiquitous to all living organisms on earth. α-amino acids can exist in D and L form, although the majority are naturally L-amino acids. Both the natural and non-natural amino acids have many uses in organic chemistry as chiral starting materials for natural product total synthesis, as chiral auxiliaries, catalysts or ligands. In protein engineering they can be incorporated into proteins in order to study protein structure and function. They may also be used as drugs that are not degraded as quickly as natural amino acids by protease enzymes. There are 4 methods to obtain amino acids for commercial use which include; extraction from natural sources, chemical synthesis, fermentation and enzymatic catalysis (Ault, 2004). Extraction from natural sources engages hydrolysis with aqueous acid as the standard procedure, followed by passage of the hydrolysate over a strongly acidic ion exchange resin to capture amino acids. After the resin is washed with water, elution with aqueous ammonia frees the amino acids collected in fractions (Ault, 2004). Chemical synthesis can be carried out on a very large scale, the significant disadvantage however is that it typically gives a racemic mixture of the enantiomeric forms of the amino acid. Therefore the product of chemical synthesis must be resolved into the R and S forms and recovered. (Ault, 2004), this increases the cost of production substantially. However, chemical synthesis is ideal for the preparation of (R,S) methionine as both isomers are metabolised by poultry and swine in contrast to the majority of amino acids, chemical synthesis is thus the predominant method for the industrial production of methionine. (Ault, 2004) All amino acids can be prepared via fermentation, whether they will or not depends on the costs of competing technologies (Ikeda, 2009). Bacterial strains that produce amino acids are mainly derived from Corynebacterium sp., Baccilus sp. or E.coli. Strains used in production are wild-type natural overproducers, auxotrophic or regulatory mutants that have altered feedback inhibition pathways, or derepressed enzyme synthesis, and/or genetically engineered organisms that have multiple copies of genes encoding rate-limiting enzymes (Ikeda, 2009). In enzymatic synthesis of amino acids pure enzymes are used rather than the enzyme systems of living organisms, as is the case with fermentation (Ault, 2004). The amino acid market has undergone rapid development since the 1980’s, due to cost effective production and isolation of amino acid products, specifically fermentation and enzymatic catalysis with their economic and ecological advantages responsible for the spectacular growth (Leuchtenberger 2005). Glutamine is the most abundant free amino acid in the human body and may be the main physiological nitrogen vehicle between different mammalian tissues (Mates, 2009); it is one of the few amino acids to cross the blood brain barrier. Glutamine is utilised by cells in a variety of ways including oxidation by the Krebs cycle to produce ATP, providing nitrogen for nucleotide synthesis and is a precursor for glutathione, the major non enzymatic cellular antioxidant (Yuneva, 2007). Although it is made by cells and thus classified non-essential there is a body of research suggesting that glutamine is ‘conditionally’ essential under stressful situations which causes rapid depletion of plasma glutamine levels (Mates 2009). This is significant in clinical trauma such as major surgery or

intense exercise (Mates, 2009). Intravenous glutamine supplementation is standard care when parenteral nutrition is given for critical illness and there is research supporting reduced mortality following administration to critically ill patients (Werneman, 2011).These findings support the hypothesis by...
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