High performance microbiological transformation of L-tyrosine to L-dopa by Yarrowia lipolytica NRRL-143
Sikander Ali1, Jeffry L Shultz2 and Ikram-ul-Haq1
1Institute of Industrial Biotechnology (IIB), GC University Lahore, Katchehry Road, Lahore-54000, Pakistan
2USDA-ARS, Crop Genetics and Production Research Unit, Stoneville, MS 38776, USA
The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disease, controlling changes in energy metabolism enzymes of the myocardium following neurogenic injury. Aspergillus oryzae is commonly used for L-dopa production; however, potential improvements in ease of handling, growth rate and environmental impact have led to an interest in exploiting alternative yeasts. The two important elements required for L-dopa production are intracellular tyrosinases (thus pre-grown yeast cells are required for the transformation of L-tyrosine to L-dopa) and L-ascorbate, which acts as a reducing agent.
Pre-grown cells of Yarrowia lipolytica NRRL-143 were used for the microbiological transformation of L-tyrosine to L-dopa. Different diatomite concentrations (0.5–3.0 mg/ml) were added to the acidic (pH 3.5) reaction mixture. Maximum L-dopa biosynthesis (2.96 mg/ml L-dopa from 2.68 mg/ml L-tyrosine) was obtained when 2.0 mg/ml diatomite was added 15 min after the start of the reaction. After optimizing reaction time (30 min), and yeast cell concentration (2.5 mg/ml), an overall 12.5 fold higher L-dopa production rate was observed when compared to the control. Significant enhancements in Yp/s, Qs and qs over the control were observed.
Diatomite (2.0 mg/ml) addition 15 min after reaction commencement improved microbiological transformation of L-tyrosine to L-dopa (3.48 mg/ml; p ≤ 0.05) by Y. lipolytica NRRL-143. A 35% higher substrate conversion rate was achieved when compared to the control.
BMC Biotechnology 2007, 7:50doi:10.1186/1472-6750-7-50. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0.