Xu Jian, Bao Jia-Wei, Su Xian-Feng, Zhang Hong-Jian, Zeng Xin, Tang Lei, Wang Ke, Zhang Jian-Hua, Chen Xu-Sheng, Mao Zhong-Gui
The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.
Bioprocess Biosyst Eng. 2016 Mar;39(3):391-400. doi: 10.1007/s00449-015-1522-4. Epub 2015 Dec 12.
In this study, an integrated citric acid-methane fermentation process was established to solve the problem of wastewater treatment in citric acid production. Citric acid wastewater was treated through anaerobic digestion and then the anaerobic digestion effluent (ADE) was further treated and recycled for the next batch citric acid fermentation. This process could eliminate wastewater discharge and reduce water resource consumption. Propionic acid was found in the ADE and its concentration continually increased in recycling. Effect of propionic acid on citric acid fermentation was investigated, and results indicated that influence of propionic acid on citric acid fermentation was contributed to the undissociated form. Citric acid fermentation was inhibited when the concentration of propionic acid was above 2, 4, and 6 mM in initial pH 4.0, 4.5 and, 5.0, respectively. However, low concentration of propionic acid could promote isomaltase activity which converted more isomaltose to available sugar, thereby increasing citric acid production. High concentration of propionic acid could influence the vitality of cell and prolong the lag phase, causing large amount of glucose still remaining in medium at the end of fermentation and decreasing citric acid production.
在本研究中，建立了一种柠檬酸 - 甲烷综合发酵工艺，以解决柠檬酸生产中的废水处理问题。柠檬酸废水通过厌氧消化进行处理，然后对厌氧消化出水（ADE）进行进一步处理并循环用于下一批柠檬酸发酵。该工艺可以消除废水排放并减少水资源消耗。在ADE中发现了丙酸，并且其浓度在循环过程中持续增加。研究了丙酸对柠檬酸发酵的影响，结果表明丙酸对柠檬酸发酵的影响主要归因于未解离形式。当丙酸浓度在初始pH值为4.0、4.5和5.0时分别高于2 mM、4 mM和6 mM时，柠檬酸发酵受到抑制。然而，低浓度的丙酸可以促进异麦芽糖酶的活性，将更多的异麦芽糖转化为可利用的糖，从而增加柠檬酸的产量。高浓度的丙酸会影响细胞活力并延长延迟期，导致发酵结束时培养基中仍残留大量葡萄糖，从而降低柠檬酸产量。
