乙、丁酸添加条件下丁醇发酵图论模型的构建

Model Construction for Butanol Fermentations with Acetate/Butyrate Added by Graph Theory

有机酸代谢途径在丁醇发酵过程中具有重要的作用,对细胞内碳流的分配和产物的合成影响显著。在7 L厌氧发酵罐中,进行了间歇添加乙酸或丁酸的发酵实验。结果表明,乙、丁酸的添加显著提高了总溶剂的生产效率,分别提高了47.1%和39.2%;此外,丁醇/丙酮比在添加丁酸的批次中提高了21.7%,在添加乙酸的批次中降低了16.2%;厌氧瓶中的发酵实验也证实了以上结果。有机酸代谢计算的结果表明,乙、丁酸的添加基本上阻断了相应有机酸闭环的吸收途径。基于相关报道和代谢计算结果,构建了针对乙、丁酸添加批次的图论模型,并利用该模型对不同发酵条件下的溶剂浓度和丁醇/丙酮比进行了计算。结果表明,该模型很好地预测了实验结果,合理地构建了乙、丁酸添加批次的信号传递线图。

Acetate/butyrate metabolic pathways play an important role in ABE fermentation and their changes will influence entire carbon fluxes distribution. Several fermentations with intermittent feeding of acetate/butyrate were conducted in a 7 L fermentor and the results indicated that exogenous acetate/butyrate enhanced solvents productivities by 47.1% and 39.2% respectively, and butanol/acetone ratios were improved by 21.7% for butyrate added batch and decreased by 16.2% for acetate added batch. A nonlinear constraint was utilized for acids rates calculation and the results revealed that acetate/butyrate formation pathways were almost blocked by corresponding acids feeding. Then a metabolic model constructed by graph theory was utilized to dispose those cases with acetate/ butyrate added and to predict solvents production, in which some improvements were adopted based on the calculation results and related references. The model predicted solvents production, butanol/acetone ratios accurately and constructed the directed signal flow diagrams of ABE network under different conditions correctly.