PHOTO-REGULATED ASTAXANTHIN PRODUCTION BY PHAFFIA-RHODOZYMA MUTANTS

Astaxanthin production by Phaffia rhodozyma mutants was photo-inducible. The intracellular astaxanthin concentration during cultivation in the dark was almost constant in the different mutants and did not reflect the concentrations reached in cells grown in the light, which differed considerably among these mutants. The final astaxanthin concentration obtained was determined by the total time of illumination, the growth phase subjected to illumination and the light intensity. Higher astaxanthin levels were obtained when cells were illuminated during the exponential growth phase. Subjecting cells to a 15 min light pulse greatly enhanced pigment production, but the stimulation was of a transient nature and a reduction in total pigment content was observed when the cultures were returned to the dark. The maximum astaxanthin production was obtained when cultures were continuously illuminated at moderate light intensities (5 to 100 muE.m-2.s-1). Blue light was primarily responsible for photo-induced astaxanthin production in P. rhodozyma.