Optimized fed-batch cultivation of Rhodotorula toruloides in a bubble column bioreactor progressed the β-carotene production from corn steep liquor.

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 .