Enzymatic synthesis of selected amino acid esters of sugars

Lohith, K. (2006) Enzymatic synthesis of selected amino acid esters of sugars. PhD thesis, University of Mysore.

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Abstract

The main scope of the present work is to use the lipases in esterification reactions to prepare commercially important esters. Amino acyl esters of carbohydrates, exhibit a large number of applications. They can be used as antibiotics,detergents, sweetening agents, microcapsules in pharmaceutical reagents, in delivery of biological active amino acid esters, anti tumor agents and antiviral nucleoside amino acid esters. Literature survey indicates that lipase catalysed synthesis of amino acyl esters of carbohydrates are very few (Park et al. 1999; 1996; Boyer et al. 2001; Maruyama et al. 2002; Vijyakumar et al. 2004; Lohith and Divakar 2004). The available literature deals with N-protected and carboxyl group activated amino acids and carbohydrates. The reported protocols exhibit some severe limitations. Most of researchers have employed proteases for their work (Boyer et al. 2001; Park et al. 1999; 1996; Riva et al. 1986). Protected and carboxyl group activated amino acids and carbohydrates have been employed (Park et al. 1999; 1996). Reactions were carried out with health hazardous solvents like dimethyl sulphoxide, pyridine and dimethylformamide. Most of the reports are from experiments carried out in shake flask levels with large amount of enzyme being employed in such reactions (Riva et al. 1986). Lipases have been reported to give insignificant results in preparing amino acyl esters of carbohydrates (Park et al. 1996). Commercially available lipases, which are also economically viable were employed in the present work. Use of unprotected and unactivated amino acids and carbohydrates have been employed for the reactions, which effectively reduce the number of acylation and deacylation steps. Low boiling solvents were employed for the reactions such that solvents can be recovered by distilling. The work out procedures were easy and the product recovery involved very few unit operations. Smaller amounts of enzyme and larger amounts substrates were employed to obtain high yields than the reported. All the reactions were carried out in presence of solvent mixtures using an experimental set up, which maintained a very low water activity, very much essential for high enzyme activity and for carrying out reactions in a large-scale level as well. The present work describes synthesis of L-phenylalanyl, L-tryptophanyl, Lhistidyl and L-prolyl esters of aldohexoses (D-glucose, D-galactose and D-mannose),ketohexose (D-fructose), pentoses (D-arabinose and D-ribose), disaccharides (lactose, maltose and sucrose) and sugar alcohols (D-sorbitol and D-mannitol) using lipases from Rhizomucor miehei, porcine pancreas and Candida rugosa in organic solvents. Various effects of enzyme, substrate and buffer concentrations, pH, enzyme reusability, kinetics, regio and stereo selectivity were investigated. The isolated product esters were also tested for probable pharmaceutical activity as well. Thus the full potentialities of lipases are brought out in this study which describes the synthesis of several amino acyl esters of carbohydrates for the first time using lipases from Rhizomucor miehei, porcine pancreas and Candida rugosa.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Candida rugosa Rhizomucor miehei Lipases Enzymes amino acid esters Enzymatic synthesis
Subjects:	500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 16 Enzyme Chemistry
Divisions:	Fermentation Technology and Bioengineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	03 Dec 2007 06:10
Last Modified:	28 Dec 2011 09:31
URI:	http://ir.cftri.res.in/id/eprint/1526

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