Spent sulphite liquor (SSL), a by-product stream produced by the pulp and paper industry, contains significant quantities of hemicellulose sugars (mainly xylose) and lignosulphonate calcium salts. Lignosulphonates are currently isolated from the SSL and used in various applications including concrete production. However, during the isolation of lignosulphonates the sugars are destroyed. The conventional pulp and paper industry could be restructured into a novel biorefinery through the exploitation of SSL for the production of lignosulphonates and fermentation products by exploiting the C5 and C6 sugar content of SSL. In order to achieve this, the development of efficient pre-treatment of SSL is necessary. This study evaluates the application of membrane fractionation of SSL via ultrafiltration using three membranes (Merck Millipore) with 10 kDa, 5 kDa and 3 kDa molecular weight cut-offs, respectively. Sugars, acetic acid, lignosulphonates and phenolics were quantitated in both permeate and retentate streams. The membrane with 5 kDa molecular weight cut-off leads to significant reduction of lignosulphonate concentration in the permeate stream.  The permeate stream was used as a source of sugars for the production of succinic acid. Two bacterial strains, Actinobacillus succinogenes and Basfia succiniciproducens, were employed in both batch and fed-batch cultivations using either SSL or permeate streams produced via ultrafiltration with different molecular weight cut-offs. Fed-batch fermentations were also carried out using pure mixed sugars in order to verify the succinic acid production efficiency of the two strains in the absence of inhibitors. Ultrafiltration of SSL provided an efficient pre-treatment process for the production of both lignosulphonates and succinic acids.

Pretreatment of pulp and paper industry by-product stream for the production of lignosulphonates and succinic acid

247th National Meeting (2014)

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