Activation of torularhodin production by Rhodotorula glutinis using weak white light irradiation

The effects of the irradiation of weak white light on the growth of the red yeast Rhodotorula glutinis and its production of carotenoids were investig ated. The ability of beta -carotene and torularhodin, which are final produ cts of carotenoid biosynthesis in R. glutinis, to quench singlet oxygen has also been investigated. Weak white light irradiation that has no effect on the growth of Saccharomyces cerevisiae inhibited the growth of R. glutinis . Simultaneously, the production of torularhodin by R. glutinis markedly in creased. In a mutant of R. glutinis, which exhibited increased production o f torularhodin, an increase in torularhodin production was shown as a resul t of light irradiation during the logarithmic growth phase. An experiment u sing 3-(1,4-epidioxyl-4-methyl-1,4-dehydro-1-naphtyl) propionic acid clarif ied that torularhodin inhibited 2,5-diphenyl-3,4-benzofran decomposition by singlet oxygen quenching more strongly than did beta -carotene. This resul t is consistent with the report that carotenoids having a longer polyene ch ain may exhibit a more potent ability to quench singlet oxygen. These resul ts suggest that the biosynthesis of carotenoids in R. glutinis may play an important role in protecting against oxidative damage caused by light irrad iation, and in particular, torularhodin which has a potent singlet oxygen q uenching ability may be important. We suggest that acquisition of the abili ty to produce torularhodin may be an important property for this yeast to p romote its wider distribution in the natural world.