Process development for efficient biosynthesis of L-DOPA with recombinant Escherichia coli harboring tyrosine phenol lyase from Fusobacterium nucleatum.

The tyrosine phenol lyase (TPL) catalyzed synthesis of L-DOPA was regarded as one of the most economic route for L-DOPA synthesis. In our previous study, a novel TPL from Fusobacterium nucleatum (Fn-TPL) was exploited for efficient biosynthesis of L-DOPA. However, the catalytic efficiency decreased when the reaction system expanded from 100 mL to 1 L. As such, the bioprocess for scale-up production of L-DOPA was developed in this study. To increase the stability of substrate and product, as well as decrease the by-product formation, the optimum temperature and pH were determined to be 15 °C and pH 8.0, respectively. The initial concentration of pyrocatechol, pyruvate and ammonium acetate was fixed at 8, 5 and 77 g/L and a fed-batch approach was applied with sodium pyruvate, pyrocatechol and ammonium acetate fed in a concentration of 5, 5 and 3.5 g/L, respectively. In addition, L-DOPA crystals were exogenously added to inhibit cell encapsulation by the precipitated product. The final L-DOPA concentration reached higher than 120 g/L with pyrocatechol conversion more than 96% in a 15-L stirred tank, demonstrating the great potential of Fn-TPL for industrial production of L-DOPA.

Optimization of process parameters for the production of tyrosine phenol lyase by Citrobacterfreundii MTCC 2424.

The process optimization using technological combinations for the production of tyrosine phenol lyase by Citrobacter freundii MTCC 2424 has been carried out in this study. The maximum production of tyrosine phenol lyase (0.15 U) was obtained by culturing C. freundii MTCC 2424 in a medium containing (g/l) meat extract 5.0, yeast extract 5.0, peptone 2.5, and l-tyrosine 1.0 at 25 degrees C for 16 h in a temperature controlled orbital shaker. A 2.5-fold increase in enzyme activity with 1.3-fold decrease in the cost of enzyme production (in terms of media components) was achieved by using different technological combinations. The process optimization using technological combinations allowed quick optimization of large number of variables, which helps in designing of suitable fermentation conditions for the cost-effective production of tyrosine phenol lyase. Moreover, this also provides information for balancing the nutrient concentration with minimum experimentation.

A novel microbial interaction: obligate commensalism between a new gram-negative thermophile and a thermophilic Bacillus strain.

Obligately commensal interaction between a new gram-negative thermophile and a thermophilic Bacillus strain was investigated. From compost samples, a mixed culture showing tyrosine phenol-lyase activity was enriched at 60 degrees C. The mixed culture consisted of a thermophilic gram-negative strain, SC-1, and a gram-positive spore-forming strain, SK-1. In mixed cultures, strain SC-1 started to grow only when strain SK-1 entered the stationary phase. Although strain SC-1 showed tyrosine phenol lyase activity, we could not isolate a colony with any nutrient medium. For the isolation and cultivation of strain SC-1, we added culture supernatant and cell extract of the mixed culture to the basal medium. The supernatant and cell extract of the mixed culture contained heat-stable and heat-labile factors, respectively, that are essential to the growth of strain SC-1. During pure cultures of strain SK-1, the heat-stable growth factors were released during the growth phase and the heat-labile growth factors were produced intracellularly at the early stationary phase. Strain SC-1 was gram-negative and microaerophilic, and grows optimally at 60 degrees C. Based on these results, we propose a novel commensal interaction between a new gram-negative thermophile, strain SC-1, and Bacillus sp. strain SK-1.

Transcriptional regulation of tyrosine phenol-lyase gene of Erwinia herbicola AJ2985.

Induction and repression of tyrosine phenol-lyase (TPL; EC 4.1.99.2) of Erwinia herbicola AJ2985 were examined on the transcriptional level and it was shown that transcription of tpl was increased by the addition of tyrosine and decreased by the addition of glucose in the medium. The 5' flanking region of its gene, tpl, was analyzed and its transcriptional start point was determined. A presumed -35, -10 promoter region, TyrR box, and operator-like region were also found in this region.

Thermostable tyrosine phenol-lyase of Symbiobacterium sp. SC-1: gene cloning, sequence determination, and overproduction in Escherichia coli.

During the screening for tyrosine phenol-lyase-producing thermophiles, we isolated an obligatory symbiotic thermophile, Symbiobacterium sp. SC-1, which grew only in coculture with Bacillus sp. SK-1. A gene encoding thermostable tyrosine phenol-lyase (TPL) was cloned from the genomic DNA of the Symbiobacterium sp. SC-1 and the nucleotide sequence of the TPL structural gene was determined. The gene consists of 1374 base pairs encoding a polypeptide of 458 amino acid residues; the molecular mass of the enzyme subunit is estimated to be 52,196 Da. The structural gene of TPL was amplified by PCR, blunt-ended, and ligated into the NcoI-HindIII site of plasmid pTrc99A to construct an expression vector for the overproduction of the thermostable TPL. The level of thermostable TPL production was about 15% of the total soluble proteins of Escherichia coli extract. The enzyme was purified to homogeneity from the E. coli extract with an overall yield of 48%.