State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
Biotechnol Biofuels. 2014 Jan 8;7(1):5. doi: 10.1186/1754-6834-7-5.
Clostridium acetobutylicum can propagate on fibrous matrices and form biofilms that have improved butanol tolerance and a high fermentation rate and can be repeatedly used. Previously, a novel macroporous resin, KA-I, was synthesized in our laboratory and was demonstrated to be a good adsorbent with high selectivity and capacity for butanol recovery from a model solution. Based on these results, we aimed to develop a process integrating a biofilm reactor with simultaneous product recovery using the KA-I resin to maximize the production efficiency of biobutanol.
KA-I showed great affinity for butanol and butyrate and could selectively enhance acetoin production at the expense of acetone during the fermentation. The biofilm reactor exhibited high productivity with considerably low broth turbidity during repeated batch fermentations. By maintaining the butanol level above 6.5 g/L in the biofilm reactor, butyrate adsorption by the KA-I resin was effectively reduced. Co-adsorption of acetone by the resin improved the fermentation performance. By redox modulation with methyl viologen (MV), the butanol-acetone ratio and the total product yield increased. An equivalent solvent titer of 96.5 to 130.7 g/L was achieved with a productivity of 1.0 to 1.5 g · L-1 · h-1. The solvent concentration and productivity increased by 4 to 6-fold and 3 to 5-fold, respectively, compared to traditional batch fermentation using planktonic culture.
Compared to the conventional process, the integrated process dramatically improved the productivity and reduced the energy consumption as well as water usage in biobutanol production. While genetic engineering focuses on strain improvement to enhance butanol production, process development can fully exploit the productivity of a strain and maximize the production efficiency.
丙酮丁醇梭菌可以在纤维基质上繁殖并形成生物膜，从而提高丁醇耐受性、发酵速率，并可重复使用。此前，我们实验室合成了一种新型大孔树脂 KA-I，该树脂对丁醇具有良好的吸附选择性和容量，可从模型溶液中回收丁醇。基于这些结果，我们旨在开发一种工艺，将生物膜反应器与同时使用 KA-I 树脂从发酵液中回收产物相结合，以最大限度地提高生物丁醇的生产效率。
KA-I 对丁醇和丁酸具有很大的亲和力，在发酵过程中可以选择性地提高乙酰丁醇的产量，而降低丙酮的产量。在重复分批发酵过程中，生物膜反应器表现出较高的生产力，同时发酵液的浊度较低。通过将生物膜反应器中的丁醇水平维持在 6.5g/L 以上，可以有效减少 KA-I 树脂对丁酸的吸附。树脂对丙酮的共吸附提高了发酵性能。通过使用甲紫精（MV）进行氧化还原调节，提高了丁醇-丙酮比和总产物得率。通过氧化还原调节，丁醇-丙酮比和总产物得率分别提高到 1.0 到 1.5g/L/h 和 96.5 到 130.7g/L。与使用浮游培养的传统分批发酵相比，溶剂浓度和生产力分别提高了 4 到 6 倍和 3 到 5 倍。
与传统工艺相比，该集成工艺大大提高了生产力，降低了生物丁醇生产中的能耗和用水量。虽然基因工程专注于通过遗传改造提高菌株的丁醇产量，但工艺开发可以充分利用菌株的生产力，最大限度地提高生产效率。
