Wang Xiao-Li, Sun Ya-Qin, Pan Duo-Tao, Xiu Zhi-Long
MOE Key Laboratory of Bio-Intelligent Manufacturing, School of Bioengineering, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi District, Dalian, 116024, Liaoning, People's Republic of China.
Institute of Information and Engineering, Shenyang University of Chemical Technology, Shenyang, 110142, Liaoning, People's Republic of China.
Biotechnol Biofuels Bioprod. 2024 Mar 7;17(1):38. doi: 10.1186/s13068-024-02486-5.
Glycerol, as a by-product, mainly derives from the conversion of many crops to biodiesel, ethanol, and fatty ester. Its bioconversion to 1,3-propanediol (1,3-PDO) is an environmentally friendly method. Continuous fermentation has many striking merits over fed-batch and batch fermentation, such as high product concentration with easy feeding operation, long-term high productivity without frequent seed culture, and energy-intensive sterilization. However, it is usually difficult to harvest high product concentrations.
In this study, a three-stage continuous fermentation was firstly designed to produce 1,3-PDO from crude glycerol by Clostridium butyricum, in which the first stage fermentation was responsible for providing the excellent cells in a robust growth state, the second stage focused on promoting 1,3-PDO production, and the third stage aimed to further boost the 1,3-PDO concentration and reduce the residual glycerol concentration as much as possible. Through the three-stage continuous fermentation, 80.05 g/L 1,3-PDO as the maximum concentration was produced while maintaining residual glycerol of 5.87 g/L, achieving a yield of 0.48 g/g and a productivity of 3.67 g/(L·h). Based on the 14 sets of experimental data from the first stage, a kinetic model was developed to describe the intricate relationships among the concentrations of 1,3-PDO, substrate, biomass, and butyrate. Subsequently, this kinetic model was used to optimize and predict the highest 1,3-PDO productivity of 11.26 g/(L·h) in the first stage fermentation, while the glycerol feeding concentration and dilution rate were determined to be 92 g/L and 0.341 h, separately. Additionally, to achieve a target 1,3-PDO production of 80 g/L without the third stage fermentation, the predicted minimum volume ratio of the second fermenter to the first one was 11.9. The kinetics-based two-stage continuous fermentation was experimentally verified well with the predicted results.
A novel three-stage continuous fermentation and a kinetic model were reported. Then a simpler two-stage continuous fermentation was developed based on the optimization of the kinetic model. This kinetics-based development of two-stage continuous fermentation could achieve high-level production of 1,3-PDO. Meanwhile, it provides a reference for other bio-chemicals production by applying kinetics to optimize multi-stage continuous fermentation.
甘油作为一种副产品，主要来源于多种作物转化为生物柴油、乙醇和脂肪酸酯的过程。将其生物转化为1,3 - 丙二醇（1,3 - PDO）是一种环保方法。连续发酵相对于分批补料发酵和分批发酵具有许多显著优点，如产品浓度高且进料操作简便、无需频繁接种培养即可长期保持高生产率以及避免耗能大的灭菌操作。然而，通常难以获得高产品浓度。
在本研究中，首次设计了一种三段连续发酵工艺，利用丁酸梭菌从粗甘油生产1,3 - PDO，其中第一阶段发酵负责提供处于强劲生长状态的优良细胞，第二阶段着重促进1,3 - PDO的生产，第三阶段旨在进一步提高1,3 - PDO浓度并尽可能降低残余甘油浓度。通过三段连续发酵，最高生产出80.05 g/L的1,3 - PDO，同时残余甘油为5.87 g/L，产率达到0.48 g/g，生产率为3.67 g/(L·h)。基于第一阶段的14组实验数据，建立了动力学模型以描述1,3 - PDO、底物、生物质和丁酸盐浓度之间的复杂关系。随后，该动力学模型用于优化和预测第一阶段发酵中最高1,3 - PDO生产率为11.26 g/(L·h)，同时确定甘油进料浓度和稀释率分别为92 g/L和0.341 h⁻¹。此外，为了在不进行第三阶段发酵的情况下实现80 g/L的目标1,3 - PDO产量，预测第二发酵罐与第一发酵罐的最小体积比为11.9。基于动力学的两段连续发酵在实验上得到了很好的验证，与预测结果相符。
报道了一种新型三段连续发酵工艺和一个动力学模型。然后基于动力学模型的优化开发了一种更简单的两段连续发酵工艺。这种基于动力学的两段连续发酵工艺开发能够实现1,3 - PDO的高水平生产。同时，它为通过应用动力学优化多阶段连续发酵生产其他生物化学品提供了参考。
