Development of Bioreactor System for L-Tyrosine Synthesis Using Thermostable Tyrosine Phenol-Lyase

• Published in: Journal of microbiology and biotechnology Vol. 17; no. 1; pp. 116 - 122
• Main Authors: Kim, Do-Young, Rha, Eugene, Choi, Su-Lim, Song, Jae-Jun, Hong, Seung-Pyo, Sung, Moon-Hee, Lee, Seung-Goo
• Format: Journal Article
• Language: Korean
• Published: 한국미생물생명공학회 30.01.2007
• Subjects: bioconversion; fed-batch; L-tyrosine; Symbiobacterium toebii; Tyrosine phenol-Lyase; Symbiobacterium toebii; L-tyrosine; fed-batch; Tyrosine phenol-lyase; bioconversion
• ISSN: 1017-7825; 1738-8872

An efficient enzyme system for the synthesis of L-tyrosine was developed using a fed-batch reactor with continuous feeding of phenol, pyruvate, and ammonia. A thermo- and chemostable tyrosine phenol-lyase from Symbiobacterium toebii was employed as the biocatalyst in this work. The enzyme was produced using a constitutive expression system in Escherichia coli BL21, and prepared as a soluble extract by rapid clarification, involving treatment with 40% methanol in the presence of excess ammonium chloride. The stability of the enzyme was maintained for at least 18 h under the synthesis conditions, including 75 mM phenol at pH 8.5 and $40^{\circ}C$. The fed-batch system (working volume, 0.51) containing 1.0 kU of the enzyme preparation was continuously fed with two substrate preparations: one containing 2.2 M phenol and 2.4 M sodium pyruvate, and the other containing 0.4 mM pyridoxal-5-phosphate and 4M ammonium chloride (pH 8.5). The system produced 130g/I of L-tyrosine within 30h, mostly as precipitated particles, upon continuous feeding of the substrates for 22 h. The maximum conversion yield of L-tyrosine was 94% on the basis of the supplied phenol.