Continuous-flow fermentation of sugar into ethanol using immobilized yeast
1985
Del Rosario, E.J. | Elegado, F.B. | Pamatong, F.V. (Philippines Univ., Los Banos, College, Laguna (Philippines). National Inst. of Biotechnology and Applied Microbiology)
Ipil-ipil (Leucaena leucocephala) wood sawdust and shavings and kappa-carragienan gel were used separately or in a mixture for immobilizing Saccharomyces cerevisiae BB 1945 and the immobilized yeast was utilized for the continuous-flow ethanol fermentation of sugarcane molasses. Kappa-carragienan was the best carrier; at a yeast loading of 30 g/l gel a volumetric productivity of 11.5-16.6 g ethanol per liter per hour was obtained during 67 days of continuous culture. Average values of fermentation efficiency and alcohol concentration in the 'beer' were 92% and 7.7% (w/v), respectively, at a fermenter residence time of six hours. Non-pasteurization of the molasses feed and the use of fertilizer grade ammonium phosphate as the only nutrient supplement reduced the ethanol productivity by less than 1 g/1-hr. Banana pulp juice from ripe Cavendish banana fruits was extracted by either manual or mechanical pressing. The juice had a pH of 4.9-5.0 and contained 12.4-12.8% (w/v) total sugars. After supplementation with ammonium sulfate, sodium phosphate and magnesium sulfate, the juice was fermented into ethanol using yeast immobilized on kappa-carragienan gel. The volumetric productivity and fermentation efficiency were about 15 g/l-h and 94%, respectively. The concentrations of alcohol and residual sugar in the 'beer' were 54 g/l and 12.8-14.5 g/l, respectively.
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