title: Continuous succinic acid production from xylose by Actinobacillus succinogenes.
abstract: Continuous, anaerobic fermentations of D-xylose were performed by Actinobacillus succinogenes 130Z in a custom, biofilm reactor at dilution rates of 0.05, 0.10 and 0.30 h(-1). Succinic acid yields on xylose (0.55-0.68 g g(-1)), titres (10.9-29.4 g L(-1)) and productivities (1.5-3.4 g L(-1) h(-1)) were lower than those of a previous study on glucose, but product ratios (succinic acid/acetic acid = 3.0-5.0 g g(-1)) and carbohydrate consumption rates were similar. Also, mass balance closures on xylose were up to 18.2 % lower than those on glucose. A modified HPLC method revealed pyruvic acid excretion at appreciable concentrations (1.2-1.9 g L(-1)) which improved the mass balance closure by up to 16.8 %. Furthermore, redox balances based on the accounted xylose consumed and the excreted metabolites, indicated an overproduction of reducing power. The oxidative pentose phosphate pathway was shown to be a plausible source of the additional reducing power.
authors.affiliation: Department of Chemical Engineering, University of Pretoria, Lynnwood Road, Hatfield, Pretoria, 0002, South Africa. michael.bradfield@tuks.co.za.
authors.forename: Michael F A
authors.initials: MF
authors.lastname: Bradfield
authors.affiliation: Department of Chemical Engineering, University of Pretoria, Lynnwood Road, Hatfield, Pretoria, 0002, South Africa. willie.nicol@gmail.com.
authors.forename: Willie
authors.initials: W
authors.lastname: Nicol
mesh_terms: D000188:Actinobacillus / Q000254:growth & development*; D000693:Anaerobiosis / Q000502:physiology; D019802:Succinic Acid / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D014994:Xylose; D019802:Succinic Acid
keywords: Actinobacillus succinogenes; Biofilm; Continuous fermentation; Redox balance; Succinic acid; Xylose