Catalytic resolution of dl-tryptophan amides using the resting cells of Flavobacterium aquatile ZJB-09211 in a two-phase system

•Ethyl acetate enhanced the activity of amidase and facilitated product separation.•Space-time yield of the bioprocess was improved in this two-phase reaction system.•This methodology may play a pivot role in large scale production of L-tryptophan.

The catalytic activity of Flavobacterium aquatile ZJB-09211 towards the kinetic resolution of DL-tryptophan amides was significantly enhanced by ethyl acetate. A maximum enzyme activity of 5118.62 U/g was obtained under the optimized conditions consisting of a mixture of ethyl acetate and Tris–HCl buffer (30:70). In a scale-up reaction, the tryptophan amide concentration was improved to 200 mM, with 49.85% (e.e. > 99.95%) of the substrate being converted to l-tryptophan. The addition of an organic solvent to the process therefore provided an effective approach for improving the activity of the amidase that could be applied to other amidase-catalyzed bioprocesses.

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