A novel process of ethanol production accompanied by extraction of sugar in cane chips

Abstract

By connecting a rhomboid unit for fermentation and an exchangeable tubular unit for extraction, a novel bioreactor was designed to produce high concentration of ethanol solution from non-peeled sugar cane chips by means of a cyclic system for exchanging old chips with new ones. The rhomboid and tubular units were packed with 1.0–1.5 mm biocatalyst entrapped yeast-cells with Al alginateand cane chips of 2.0–3.0 mm in width, respectively. The volume ratio of the two units was 1.0. At the start of the first cycle, 2 g/l of Al₂(SO₄)₃ 14–18 H₂O solution was added to the bioreactor, where the ratio of the solution to the working volume was 0.85. Both sugar extraction and fermentation were anaerobically performed at pH 2.5 and a temperature of 30°C by circulating the solution through the two units. After each cycle, the tubular unit was exchanged for a new unit packed with new chips. The combined solution of free ethanol and the ethanol obtained by pressing the old chips was re-used as the circulating solution.

When the volume ratio of the biocatalyst to the total working volume was 0.1 and the amount of dried cane chips in the tubular unit was 200 g/l, 16% (w/v) ethanol was produced after 7 cycles. Each cycle was established at about 20 h. The number of free cells in the circulating solution was only 2×10⁷/ml after 7 cycles.