Optimized fed-batch cultivation of Rhodotorula toruloides in a bubble column bioreactor progressed the β-carotene...

In this work, a new isolate yeast, namely Rhodotorula toruloides KP324973, was examined for β-carotene production from corn steep liquor (CSL) as a sole carbon source because CSL as the by-product of corn wet-milling process mainly enriched from the water-soluble carbohydrates. The studies were preliminary performed at the shaken flasks, and then developed at batch and fed-batch modes in a bubble column reactor (BCR). Application of the BCR improved the carotenogenesis of the cells in comparison with shaken flasks and the specific β-carotene production rate (R_p) and the yield of β-carotene production from the total reducing sugars (Y_P/TRS) reached 2.23 mg g_cell^-1 h^-1 and 36.82 mg g_TRS^-1, respectively. Further studies were carried out to optimize the operational factors of the BCR for a fed-batch production by the response surface methodology. An optimal condition at a feed flow rate of 2.5 mL h^-1, temperature 11.7°C, and initial pH of 6.1 obtained the highest R_p = 12.31 mg g_cell^-1 h^-1 and Y_P/TRS = 97.18 mg g_TRS^-1.