Blesken Christian C, Strümpfler Tessa, Tiso Till, Blank Lars M
iAMB-Institute of Applied Microbiology, ABBt-Aachen Biology and Biotechnology, RWTH Aachen University, 52074 Aachen, Germany.
Microorganisms. 2020 Dec 18;8(12):2029. doi: 10.3390/microorganisms8122029.
The production of biosurfactants is often hampered by excessive foaming in the bioreactor, impacting system scale-up and downstream processing. Foam fractionation was proposed to tackle this challenge by combining in situ product removal with a pre-purification step. In previous studies, foam fractionation was coupled to bioreactor operation, hence it was operated at suboptimal parameters. Here, we use an external fractionation column to decouple biosurfactant production from foam fractionation, enabling continuous surfactant separation, which is especially suited for system scale-up. As a subsequent product recovery step, continuous foam adsorption was integrated into the process. The configuration is evaluated for rhamnolipid (RL) or 3-(3-hydroxyalkanoyloxy)alkanoic acid (HAA, i.e., RL precursor) production by recombinant non-pathogenic KT2440. Surfactant concentrations of 7.5 g/L and 2.0 g/L were obtained in the fractionated foam. 4.7 g RLs and 2.8 g HAAs could be separated in the 2-stage recovery process within 36 h from a 2 L culture volume. With a culture volume scale-up to 9 L, 16 g RLs were adsorbed, and the space-time yield (STY) increased by 31% to 0.21 gRL/L·h. We demonstrate a well-performing process design for biosurfactant production and recovery as a contribution to a vital bioeconomy.
生物反应器中过度起泡常常会阻碍生物表面活性剂的生产，影响系统放大和下游加工。有人提出采用泡沫分离法来应对这一挑战，即将原位产物去除与预纯化步骤相结合。在先前的研究中，泡沫分离与生物反应器操作耦合，因此其运行参数并非最优。在此，我们使用一个外部分离柱将生物表面活性剂的生产与泡沫分离解耦，实现表面活性剂的连续分离，这特别适合系统放大。作为后续的产物回收步骤，连续泡沫吸附被整合到该过程中。对重组非致病性KT2440生产鼠李糖脂（RL）或3-(3-羟基链烷酰氧基)链烷酸（HAA，即RL前体）的配置进行了评估。在分馏泡沫中获得了7.5 g/L和2.0 g/L的表面活性剂浓度。在36小时内，从2 L培养体积中，通过两阶段回收过程可分离出4.7 g RL和2.8 g HAA。随着培养体积扩大到9 L，吸附了16 g RL，时空产率（STY）提高了31%，达到0.21 gRL/L·h。我们展示了一种用于生物表面活性剂生产和回收的性能良好的工艺设计，为重要的生物经济做出了贡献。
