Characterization of free and alginate-polylysine-alginate microencapsulated Erwinia herbicola for the conversion of ammonia, pyruvate, and phenol into L-tyrosine.
The whole cell tyrosine phenol-lyase (TPL, E.C. 4.1.99.2) activity of Erwinia herbicola (ATCC 21434) was microen-capsulated. We studied the use of this for the conversion of ammonia and pyruvate along with phenol or catechol, respectively, into L-tyrosine or dihydroxyphenyl-L-alanine (L-dopa). The reactions are relevant to the development of new methods for the production of L-tyrosine and L-dopa. The growth of E. herbicola at temperatures from 22 degrees C to 32 degrees C is stable, since at these temperatures the cells grow up to the stationary phase and remain there for at least 10 h. At 37 degrees C the cells grow rapidly, but they also enter the death phase rapidly. There is only limited growth of E. herbicola at 42 degrees C. Whole cells of E. herbicola were encapsulated within alginate-polylysine-alginate microcapsules (916 +/- 100 mum, mean +/- std. dev.). The TPL activity of the cells catalyzed the production of L-tyrosine or dihydroxyphenyl-L-alanine (L-dopa) from ammonia, pyruvate, and phenol or catechol, respectively. In the production of tyrosine, an integrated equation based on an ordered ter-uni rapid equilibrium mechanism can be used to find the kinetic parameters of TPL. In an adequately stirred system, the apparent values of-the kinetic parameters of whole cell TPL are equal whether the cells are free or encapsulated. The apparent K(M) of tyrosine varies with the amount of whole cells in the system, ranging from 0.2 to 0.3 mM. The apparent K(M) for phenol is 0.5 mM. The apparent K(M) values for pyruvate and ammonia are an order of magnitude greater for whole cells than they are for the cell free enzyme. (c) 1995 John Wiley & Sons, Inc.
Lloyd-George
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Artificial Cells and Organs Research Centre, Faculty of Medicine and Department of Chemical Engineering, McGill University, Montreal, Quebec, H3G IY6, Canada.
Chang
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