Enzymatic Production of Tryptophan Coupled to Pyruvic Acid Fermentation

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Enzymatic production of tryptophan coupled to pyruvic acid fermentation was established. Enterobacter aerogenes AHU 1540 was selected as a high tryptophanase strain, and reaction conditions for tryptophan synthesis from pyruvic acid, indole and ammonia were examined. When the reaction mixture of pH 9.0 (6N KOH) containing pyruvic acid 1.5%, indole 0.5%, NH_4Cl 1.8%, pyridoxal 5'-phosphate (PLP) 0.1 mM, Triton X-100 2.3% (v/v), CaCO_3 3%, Polypepton 1%, mineral salts and tryptophanase-induced cells of E. aerogenes 1.2mg/ml (as dry weight) in a total volume of 67 ml was incubated with shaking at 37℃, tryptophan synthesis was completed within 1 day and the final yield was 6-7 g/l. Agaricus campestris AHU 9382,which can produce pyruvic acid in amounts of 20 g/l from 5% glucose, was cultured on a reciprocal shaker at 27℃ for 3 days, then cells of E. aerogenes induced for tryptophanase were added directly to the culture broth, together with indole, NH_4Cl, PLP and a surfactant. After pH had been adjusted to 9.0 with 6 N KOH, the reaction mixture was incubated with shaking at 37℃ for 1 day. As a result, pyruvic acid was rapidly converted to tryptophan, and a yield of 6 g/l was obtained.
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