Aims: To study the mechanism of production of brown pigments from tyrosine in the yeast Yarrowia lipolytica.
Methods and results: Pigment formation was followed during growth in tyrosine medium, and the presence of the pigment precursor in the medium was assessed by evaluating pigment formation after removing the cells at different times of incubation. It was observed that the pigment precursor accumulated outside the cells during the exponential phase of growth, but pigment formation only occurred during the stationary phase of growth and resulted from the oxidation of the precursor. Pigment formation was repressed by glucose and L-glutamine, and promoted by lactic acid, L-asparagine and glycine. Spectra of 1H and 13C-NMR revealed that the brown pigment was derived from tyrosine and was a polymer composed of a core of aromatic residues.
Conclusion: The results indicate that pigments result from the extracellular accumulation and auto-oxidation of an intermediate of tyrosine catabolism.
Significance and impact of the study: This is the first report on the mechanism of pigment production from tyrosine in a yeast species.