Optimization of culture conditions for enhanced L-DOPA biotransformation in Solanum tuberosum L.

The present study investigates the production of L-3,4-dihydroxyphenylalanine (L-DOPA) using callus and cell suspension cultures of Solanum tuberosum L. Leaf explants cultured on half-strength Murashige and Skoog (MS) medium supplemented with plant growth regulators showed efficient callus induction, with the highest response observed in medium containing NAA (2.0 mg L⁻¹), kinetin (2.0 mg L⁻¹), and 2,4-D (1.0 mg L⁻¹). The resulting friable callus was successfully used to establish cell suspension cultures, which exhibited significantly higher tyrosinase activity compared to solid callus cultures.
Biotransformation studies demonstrated that L-DOPA production increased with incubation time, reaching a maximum at 36 hours. Optimization experiments revealed that substrate concentration significantly influenced production, with 5 mM L-tyrosine identified as optimal for achieving a balance between yield and conversion efficiency. Higher substrate concentrations increased total L-DOPA production but reduced conversion efficiency, likely due to enzyme saturation. Additionally, 2,4-D concentration was found to play a critical role in regulating callus growth, enzyme activity, and metabolite production.
Statistical analysis confirmed significant differences among treatments, and a strong positive correlation was observed between tyrosinase activity and L-DOPA production. The study demonstrates that Solanum tuberosum cell suspension cultures represent a promising and sustainable system for L-DOPA production. Further work on downstream processing, including isolation and purification, is recommended for potential industrial application.