Departments of Chemical and Agricultural Engineering, Purdue University West Lafayette, Indiana 47907, USA.
Biotechnol Bioeng. 1990 Jun 20;36(2):207-17. doi: 10.1002/bit.260360213.
Acetone-butanol-ethanol (ABE) fermentation was performed continuously in an immobilized cell, trickle bed reactor for 54 days without, degeneration by maintaining the pH above 4.3. Column clogging was minimized by structured packing of immobilization matrix. The reactor contained two serial glass columns packed with Clostridium acetobutylicum adsorbed on 12- and 20-in.-long polyester sponge strips at total flow rates between 38 and 98.7 mL/h. Cells were initially grown at 20 g/L glucose resulting in low butanol (1.15 g/L) production encouraging cell growth. After the initial cell growth phase a higher glucose concentration (38.7 g/L) improved solvent yield from 13.2 to 24.1 wt%, and butanol production rate was the best. Further improvement in solvent yield and butanol production rate was not observed with 60 g/L of glucose. However, when the fresh nutrient supply was limited to only the first column, solvent yield increased to 27.3 wt% and butanol selectivity was improved to 0.592 as compared to 0.541 when fresh feed was fed to both columns. The highest butanol concentration of 5.2 g/L occurred at 55% conversion of the feed with 60 g/L glucose. Liquid product yield of immobilized cells approached the theoretical value reported in the literature. Glucose and product concentration profiles along the column showed that the columns can be divided into production and inhibition regions. The length of each zone was dependent upon the feed glucose concentration and feed pattern. Unlike batch fermentation, there was no clear distinction between acid and solvent production regions. The pH dropped, from 6.18-6.43 to 4.50-4.90 in the first inch of the reactor. The pH dropped further to 4.36-4.65 by the exit of the column. The results indicate that the strategy for long term stable operation with high solvent yield requires a structured packing of biologically stable porous matrix such as polyester sponge, a pH maintenance above 4.3, glucose concentrations up to 60 g/L and nutrient supply only to the inlet of the reactor.
丙酮-丁醇-乙醇（ABE）发酵在固定化细胞滴流床反应器中连续进行了 54 天，通过将 pH 值维持在 4.3 以上，细胞没有退化。通过固定化基质的结构化填充，最大限度地减少了柱堵塞。该反应器包含两个串联的玻璃柱，柱内填充有吸附在 12 英寸和 20 英寸长聚酯海绵条上的丙酮丁醇梭菌，总流速在 38 到 98.7 毫升/小时之间。细胞最初在 20 克/升葡萄糖的条件下生长，导致丁醇产量较低（1.15 克/升），但促进了细胞生长。在初始细胞生长阶段后，提高葡萄糖浓度（38.7 克/升）将溶剂得率从 13.2%提高到 24.1%，丁醇生产速率最佳。用 60 克/升葡萄糖时，溶剂得率和丁醇生产速率没有进一步提高。然而，当新鲜养分供应仅限于第一根柱子时，溶剂得率提高到 27.3%，丁醇选择性提高到 0.592，而当新鲜进料同时供应给两个柱子时，丁醇选择性为 0.541。在 60 克/升葡萄糖的进料转化率为 55%时，出现了 5.2 克/升的最高丁醇浓度。固定化细胞的液体产物得率接近文献报道的理论值。沿柱的葡萄糖和产物浓度分布表明，柱子可以分为生产区和抑制区。每个区域的长度取决于进料葡萄糖浓度和进料方式。与分批发酵不同，酸和溶剂生产区之间没有明显区别。pH 值从 6.18-6.43 降至 4.50-4.90，在反应器的第一英寸处。pH 值进一步降至 4.36-4.65，在柱的出口处。结果表明，实现高产率、长期稳定运行的策略需要使用聚酯海绵等生物稳定多孔基质进行结构化填充、将 pH 值维持在 4.3 以上、葡萄糖浓度高达 60 克/升以及仅向反应器入口供应养分。
