The photoregulation of carotenoid biosynthesis in Aspergillus giganteus mut. alba.

Aspergillus giganteus mut. alba grown in darkness produced no carotenoids, but illuminated shake cultures accumulated 170 μg·g(-1) dry weight of β-carotene. Maximum carotenoid production occurred in white light of energy fluence rate of 50 W·m(-2). Blue light, but not red light, induced β-carotene formation. A light induction period of 10 h was required for maximum β-carotene synthesis, and this was attained 48 h after illumination. 5-Fluorouracil, actinomycin D and cycloheximide prevented photoinduction of carotenogenesis, indicating that photoregulation is at the transcriptional level. Comparisons of carotenogenic enzyme activities of light- and dark-grown cultures showed that phytoene synthetase, phytoene dehydrogenase and lycopene cyclase were totally photoinduced. Photoinduction of all three carotenogenic enzymes occurred after 12 h illumination. Squalene formation increased some four-fold upon illumination.