In the present studies, Yarrowia lipolytica strain NRRL-143 was exploited for L-dopa production. The addition of 2.0 mg/ml diatomite (2:1 clay mineral) markedly improved the microbiological transformation of L-tyrosine to L-dopa. Diatomite addition 15 min after the start of reaction produced a 35% higher substrate conversion rate compared to the control (p ≤ 0.05). A biomass concentration of 2.5 mg/ml and reaction time of 30 min were also optimized. Because production of L-dopa is a high cost, low yield process, scaled up studies are a pre-requisite for commercial exploitation.