Succinic acid production by immobilized cultures using spent sulphite liquor as fermentation medium

Spent sulphite liquor (SSL) was used as carbon source for the production of succinic acid using immobilized cultures of Actinobacillus succinogenes and Basfia succiniciproducens on two different supports, delignified cellulosic material (DCM) and alginate beads. Fed-batch immobilized cultures with A. succinogenes in alginates resulted in higher sugar to succinic acid conversion yield (0.81g/g) than the respective yield achieved (0.65g/g) when DCM immobilized cultures were used. The final succinic acid concentration and yield achieved in fed-batch with immobilized cultures of B. succiniciproducens in alginates (45g/L and 0.66g/g) were higher than A. succinogenes immobilized cultures (35.4g/L and 0.61g/g) using nano-filtrated SSL as fermentation medium. Immobilized cultures of B. succiniciproducens in alginate beads were reused in four sequential fed-batch fermentations of nano-filtrated SSL leading to the production of 64.7g of succinic acid with a yield range of 0.42-0.67g/g and productivity range of 0.29-0.65g/L/h. The immobilized cultures improved the efficiency of succinic acid production as compared to free cell cultures.