Continuous Ethanol Fermentation From Molasses Using Self-flocculating Yeast Cells

Fermentation using sugarcane molasses as medium is influenced by complex components such as caramel, metal ions etc. The mono-factor effects of 4 major metal ions in YNB medium were investigated.The results show that Fe³⁺, Ca²⁺ promote ethanol ferment rate and adding moderate Cu²⁺,Zn²⁺ increase the ethanol yield. Nitrogen and phosphorus, the most important nutrient elements, were also observed to obtain the optimal growth medium composed of (NH₄)₂SO₄ 0.424g/L and KH₂PO₄ 0.342g/L. This report provides reference in order to develop the molasses fermentation in airlift suspended-bed bioreactors.Bio-ethanol, both renewable and environmentally friendly, is believed to be one of the best alternatives to petroleum-based liquid fuels. In this report, Continuous ethanol fermentation using a self-flocculating yeast strain SPSC01 was examined in a four-stage airlift bioreactors in series fermentation system with a total working volume of 4800ml. Culture substrate containing cane molasses were fed into the fermentor with four stages at the dilution rate of 0.033 h-1, 30℃. Air was supplied at a flow-rate of 0.037vvm. The average levels of 91.82 g·l^-1 for ethanol, 6.58 g·l^-1 for residual total sugar were achieved in the third stage during 50 days running when feeding 220 g·l^-1 medium mixed by molasses and brown sugar at the rate of 3:7.