Yeast strain Rhodotorula mucilaginosa F-1 was isolated from a biodiesel plant activated sludge tank.

The optimum pH and temperature for carotenoids synthesis were 5 and 25 °C, respectively.

The main components of produced carotenoids were β-carotene, torulene and torularhodin.

Metal ions supplementation improved the total amount of carotenoids and biomass growth.

Molasses might have potential as acceptable waste due to its low cost and natural carotenoids production ability.