Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
Enzyme Microb Technol. 2011 Jan 5;48(1):39-47. doi: 10.1016/j.enzmictec.2010.09.001. Epub 2010 Sep 9.
Dicarboxylic acids that are produced from renewable resources are becoming attractive building blocks for the polymers industry. In this respect, fumaric acid is very interesting. Its low aqueous solubility facilitates product recovery. To avoid excessive waste salt production during downstream processing, a low pH for fumaric acid fermentation will be beneficial. Studying the influence of pH, working volume and shaking frequency on cell cultivation helped us to identify the best conditions to obtain appropriate pellet morphologies of a wild type strain of Rhizopus oryzae. Using these pellets, the effects of pH and CO(2) addition were studied to determine the best conditions to produce fumaric acid in batch fermentations under nitrogen-limited conditions with glucose as carbon source. Decreasing either the fermentation pH below 5 or increasing the CO(2) content of the inlet air above 10% was unfavourable for the cell-specific productivity, fumaric acid yield, and fumaric acid titer. However, switching off the pH control late in the batch phase did not affect these performance parameters and allowed achieving pH of 3.6. A concentration of 20 gL(-1) of fumaric acid was obtained at pH 3.6 while the average cell mass specific productivity and fumaric acid yield were the same as at pH 5.0. Consequently, relatively modest amounts of inorganic base were required for pH control, while recovery of the acid should be relatively easy at pH 3.6.
从可再生资源中生产的二羧酸正在成为聚合物工业有吸引力的构建块。在这方面，富马酸非常有趣。其低水溶解度有利于产品回收。为了避免下游处理过程中产生过多的废盐，富马酸发酵的低 pH 值将是有益的。研究 pH 值、工作体积和摇床频率对细胞培养的影响有助于我们确定获得合适的米根霉野生型菌球形态的最佳条件。使用这些颗粒，研究了 pH 值和 CO(2)添加的影响，以确定在氮限制条件下，以葡萄糖为碳源进行分批发酵生产富马酸的最佳条件。将发酵 pH 值降低到 5 以下或将进气中 CO(2)含量增加到 10%以上，都会对细胞比产率、富马酸产率和富马酸浓度不利。然而，在分批阶段后期关闭 pH 控制不会影响这些性能参数，并允许达到 pH 值 3.6。在 pH 值为 3.6 时可获得 20 g/L 的富马酸浓度，而平均细胞质量比产率和富马酸产率与 pH 值为 5.0 时相同。因此，需要相对少量的无机碱进行 pH 控制，而在 pH 值为 3.6 时，酸的回收应该相对容易。
