FERMENTATION OF SULPHITE WASTE LIQUOR TO PRODUCE ORGANIC ACIDS

Abstract

Continuous fermentation of sulphite waste liquor by Propionibacterium arabinosum was accomplished in a system with bacterial population maintained in suspension (3.0 × 108 cells per ml) in circulating liquor, and partially as visible colonies on lump limestone. The limestone served to maintain optimum pH in the fermenting waste liquor. When the population was established, no growth substances were necessary in waste liquor feed. Recycling a portion of the fermented liquor was beneficial in obtaining rapid adjustment of pH through reaction of calcium salts of organic acids with acidic components of fresh waste liquor. The calcium lactate present in recycle liquid stimulated rate of conversion of fermentable sugar to volatile acids and aided in pH control. Conversion of fermentable sugars to volatile acids was obtained at 83.0 to 86.5% efficiency in 55 hours retention time. The volatile acids were propionic and acetic acids in 2:1 mole ratio.