Extraction of phenolic compounds and succinic acid production from spent sulphite liquor

BACKGROUND Spent sulphite liquor (SSL), the by-product stream of the acidic sulphite pulping process, contains fermentable sugars (derived from hemicellulose degradation) and various phenolic compounds. RESULTS SSL has been evaluated for the production of an antioxidant-rich fraction via liquid–liquid extraction with ethyl acetate. Design of experiments was employed in order to determine the optimum initial pH value (2.22) and solvent-to-SSL ratio (3.67:1) leading to the highest extraction of phenolic compounds (7.5 g gallic acid equivalents per L SSL). The extract showed strong antioxidant activity based on an antioxidant activity index of 3.64. The main phenolic compounds identified were ellagic and gallic acids. The removal of phenolic compounds from SSL led to higher succinic acid production efficiency by both Actinobacillus succinogenes and Basfia succiniciproducens than in the case that untreated SSL was used. CONCLUSIONS The effective removal of the phenolic compounds could result in a value-added product and at the same time this process could lead to a detoxified medium, suitable for fermentative production of succinic acid. © 2016 Society of Chemical Industry