Organic acids are an important class of building block chemicals that can be produced via microbial processes and subsequently converted into high-value chemicals and materials (Sauer et al., 2008). The wider implementation of these processes is mainly restrained by their cost. Downstream processing alone can represent up to 70% of the overall production costs (Li et al., 2016). This way, the development of economically competitive recovery processes is critical to enable the biobased production of organic acids (López-Garzón & Straathof, 2014). Additionally, the ecological footprints of the established separation techniques are far from the principles of sustainable engineering (Anastas & Zimmerman, 2003). These processes are energy demanding, consume large amounts of chemicals and generate significant loads of waste by-products (López-Garzón & Straathof, 2014). Membranes present the potential to address the energetic and environmental challenges faced by other separation techniques commonly used for the primary recovery of organic acids. In recent years, nanomembranes (molecularly thin separation layers) have become increasingly attractive and their ability to improve the efficiency of membrane processes has been demonstrated several times (Karan et al., 2015; Ling et al., 2016; Zhu et al., 2017). Due to their nanoscale thickness, nanomembranes can provide fast and high-resolution separations (Zhu et al., 2017). Additionally, the ultra-high permeance of nanomembranes can reduce both the energy consumption and other operating costs (Cheng et al., 2018).

We propose the use of ultrathin polymeric nanomembranes for the recovery of organic acids. In small-scale laboratory experiments, our research group has previously demonstrated that dense epoxy ultrathin films, with tuneable mass transfer properties, present high selectivity for organic acids (Rodler et al. 2018). To complement this preliminary study, the mass transport of small organic molecules across the ultrathin films will be analysed in detail. To ensure the membranes can be operated in crossflow filtration mode and integrated into a bioreactor, a support layer will be developed. Finally, a custom-made filtration cell will be fabricated resorting to 3D printing and connected to the small-scale bioreactor for continuous removal of organic acids.


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Cheng, X. Q., Wang, Z. X., Jiang, X., Li, T., Lau, C. H., Guo, Z., Ma, J., & Shao, L. (2018). Towards sustainable ultrafast molecular-separation membranes: From conventional polymers to emerging materials. Progress in Materials Science, 92, 258–283.

Karan, S., Jiang, Z., & Livingston, A. G. (2015). Sub–10 nm polyamide nanofilms with ultrafast solvent transport for molecular separation. Science, 348(6241), 1347–1351.

Li, Q.-Z., Feng, X.-J., Zhang, H.-B., Liu, H.-Z., Xian, M., Sun, C., Wang, J.-M., & Jiang, X.-L. (2016). Recovery Processes of Organic Acids from Fermentation Broths in the Biomass-Based Industry. Journal of Microbiology and Biotechnology, 26(1), 1–8.

Ling, S., Jin, K., Kaplan, D. L., & Buehler, M. J. (2016). Ultrathin free-standing bombyx mori silk nanofibril membranes. Nano Letters, 16(6), 3795–3800.

López-Garzón, C. S., & Straathof, A. J. J. (2014). Recovery of carboxylic acids produced by fermentation. Biotechnology Advances, 32(5), 873–904.

Rodler, A., Schuster, C., Berger, E., Tscheließnig, R., & Jungbauer, A. (2018). Freestanding ultrathin films for separation of small molecules in an aqueous environment. Journal of Biotechnology, 288(May), 48–54.

Sauer, M., Porro, D., Mattanovich, D., & Branduardi, P. (2008). Microbial production of organic acids: expanding the markets. Trends in Biotechnology, 26(2), 100–108.

Zhu, J., Qin, L., Uliana, A., Hou, J., Wang, J., Zhang, Y., Li, X., Yuan, S., Li, J., Tian, M., Lin, J., & van der Bruggen, B. (2017). Elevated performance of thin film nanocomposite membranes enabled by modified hydrophilic MOFs for nanofiltration. ACS Applied Materials and Interfaces, 9(2), 1975–1986.