Comparative study of d-xylose conversion to ethanol by immobilized growing or non-growing cells of the yeast Pachysolen tannophilus |
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Authors: | G Amin G Khallafalla H W Doelle |
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Institution: | (1) Biotechnology Unit, Department of Microbiology, University of Queensland, 4067 St. Lucia, Q., Australia;(2) Present address: Department of Microbiology, University of Maryland, 20783 College Park, MD, USA |
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Abstract: | Summary The direct conversion of d-xylose to ethanol was investigated using immobilized growing and non-growing cells of the yeast Pachysolen tannophilus. Both preparations produced ethanol from d-xylose, however the d-xylose conversion to ethanol was much better with immobilized growing cells. Ethanol concentration up to 22.9 g/l and ethanol yield of 0.351 g/g of d-xylose were obtained in batch fermentation by immobilized growing cells whereas only 17.0 g/l and 0.308 g/g of d-xylose were obtained by immobilized non-growing cells. With continuous systems, immobilized growing cells were necessary for the long-term operation, since a steady state ethanol concentration of 17.7 g/l was maintained for only one week by immobilized non-growing cell reactor. With simultaneous control of aeration rate and concentrations of nitrogen sources in feed medium, immobilized growing cells of P. tannophilus showed excellent performance. At a residence time of 25 h, the immobilized cell reactor produced 26.9 g/l of ethanol from 65 g/l of d-xylose in feed medium. |
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