Enhanced productivity of nucleoside synthesis by using whole cell immobilized biocatalysts

TRELLES, JORGE, SCHOIJET, ALEJANDRA, LEWKOWICZ, ELIZABETH AND IRIBARREN, ADOLFO M.

Villa Carlos Paz, Córdoba

Congreso; XXXVIII Reunión anual SAIBBM; 2002

saibbm

Biotransformations have been successfully applied to nucleoside synthesis using free enzymes such as lipases or glycosyltransferases. These last enzymes are very attractive since particular purine or pyrimidine nucleosides can be obtained from other cheaper precursors. As in this synthesis two intracellular enzymes are necessary, the process can be improved by using whole cells. In previous reports we have demonstrated the efficiency of Escherichia coli in the synthesis of adenosine and hypoxanthine ribo-, deoxyribo-, dideoxyribo- and arabino-nuleosides, but some other microorganisms have also displayed high activity in these reaction, as we describe in this work. In view to industrial applications, it is mandatory to simplify scale up processes and therefore, the reuse of the biocatalyst becomes necessary. In order to achieve efficiently this goal, we describe here in the use of immobilised microbial whole cells in different supports as biocatalysts. In all experiments, similar yields of purine nucleosides were afforded using both free or immobilised cells, though in the last case longer times were required. Escherichia coli, Enterobacter gergoviae and Citrobacter amalonaticus entrapped on 2% agar, 2% agarose and 8% polyacrylamide were reused in repeated cycles of 2 hours. In the best case the reactions were carried out subsequently 26 times observing that formation ratios of nucleosides were maintained.