ETHANOL-PRODUCTION FROM NON-STERILIZED BEET MOLASSES BY FREE AND IMMOBILIZED SACCHAROMYCES-CEREVISIAE CELLS USING FED-BATCH CULTURE

The production of ethanol from non-sterilized beet molasses by free an d immobilized S. cerevisiae cells in batch and fed-batch culture was i nvestigated. Fed-batch culture proved to be a better fermentation syst em for the production of ethanol than batch culture. In fed-batch cult ure, both free and immobilized S. cerevisiae cells gave the same maxim um ethanol concentration (53 g/litre) at an initial sugar concentratio n of 250 g/litre and F=250 ml/h. In the free cells system the maximum ethanol productivity (3.8 g/litre h) was obtained at a substrate conce ntration of 250 g/litre and F=500 ml/h with 30.6% ethanol yield and 81 % sugars utilization. In the immobilized cells system, a maximum ethan ol productivity of 3.5 g/litre h was achieved at an initial sugar conc entration of 250 g/litre and F=500 ml/h with 31.2% ethanol yield and 7 3.3% sugars utilization. In repeated fed-batch culture, immobilized S. cerevisiae cells gave higher overall ethanol concentration compared t o the free cells. In this case, the immobilized S. cerevisiae cells in Ca-alginate beads retained their ability to produce ethanol for 8 day s.