Bradfield Michael F A, Nicol Willie
Department of Chemical Engineering, University of Pretoria, Lynnwood Road, Hatfield, Pretoria, 0002, South Africa.
Bioprocess Biosyst Eng. 2016 Feb;39(2):233-44. doi: 10.1007/s00449-015-1507-3. Epub 2015 Nov 26.
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.
琥珀酸放线杆菌130Z在定制的生物膜反应器中，以0.05、0.10和0.30 h⁻¹的稀释率对D-木糖进行连续厌氧发酵。木糖上的琥珀酸产量（0.55 - 0.68 g g⁻¹）、滴度（10.9 - 29.4 g L⁻¹）和生产率（1.5 - 3.4 g L⁻¹ h⁻¹）低于先前关于葡萄糖的研究，但产物比率（琥珀酸/乙酸 = 3.0 - 5.0 g g⁻¹）和碳水化合物消耗率相似。此外，木糖的质量平衡闭合率比葡萄糖低18.2%。一种改进的高效液相色谱法显示丙酮酸以可观的浓度（1.2 - 1.9 g L⁻¹）排泄，这使质量平衡闭合率提高了16.8%。此外，基于消耗的木糖和排泄的代谢物的氧化还原平衡表明还原力过量产生。氧化戊糖磷酸途径被证明是额外还原力的一个合理来源。
