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KMID : 0545120070170010116
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Journal of Microbiology and Biotechnology
2007 Volume.17 No. 1 p.116 ~ p.122
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Development of Bioreactor System for L-Tyrosine Synthesis Using Thermostable Tyrosine Phenol-Lyase
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Kim Do-Young
Rha Eu-Gene
Choi Su-Lim
Song Jae-Jun
Hong Seung-Pyo
Sung Moon-Hee
Lee Seung-Goo
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Abstract
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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 Eschericha 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 40oC. The fed-batch system (working volume, 0.5 l) 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 130 g/l of L-tyrosine within 30 h, 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.
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KEYWORD
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Tyrosine phenol-lyase, Symbiobacterium toebii, fed-batch, bioconversion, L-tyrosine
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