Biochemistry and Biotechnology
Wiley InterScience Backfile Collection 1832-2000
Process Engineering, Biotechnology, Nutrition Technology
Accumulation of volatile acids produced during anaerobic fermentation of distillery-spent liquor decreased the activity of Desulphovibrio desulphuricans employed in previously communicated studies; this caused a decrease in the reduction of sulphates to sulphides. An enriched strain of Desulphovibrio rubentschikii made in a synthetic mineral medium (NH4Cl, 1·0 g; MgSO4·7H2O, 2·0 g; NaCl, 10·0 g; CaSO4, 1·0 g; calcium acetate, 1·0 g; K2HPO4, 0·5 g; Mohrs' salt, trace in 1 l.) using calcium acetate as the substrate and carbon from the tap-water was gradually built up to a 3-1. volume. The amount of hydrogen sulphide in this medium was found to be 225 mg/l. The fermentation was next carried out in a synthetic medium containing volatile acids from distillery-spent liquor as the only substrate. A 3-1. fermentation set up with diluted distillery-spent liquor (300 ml or raw liquor in 3,000 ml of water), neutralized with NaOH to pH 7·2 and supplemented with calcium sulphate and 0·1 per cent urea, showed sulphide productions (calculated as milligrams of hydrogen sulphide per litre of raw distillery-spent liquid) of 2,000, 4,000 and 6,000 with 0·1, 1·0 and 2·0 per cent calcium sulphate in the charge respectively. The volatile acid content, expressed as acetic acid, was 18,564 mg/litre of raw distillery-spent liquor on an average throughout the study. The ratio of hydrogen sulphide produced per litre of raw distillery-spent liquor to the amount of volatile acids developed expressed in milliequivalents per litre of raw liquor during fermentation increased gradually from 0·1367 to 0·5567 in the presence of 0·1 to 2·0 per cent of calcium sulphate in the charge.
Type of Medium: