Immobilizing cells is a promising approach to creating efficient photosynthetic cell factories for sustainable chemical production. Here we show a novel design of a photosynthetic solid-state cell factory for sustainable biocatalytic ethylene production. We enclosed cyanobacteria in never-dried hydrogel films made from TEMPO-oxidized cellulose nanofibers (TCNF) that are cross-linked with polyvinyl alcohol (PVA) to create a self-contained matrix architecture. The matrix is ​​ready for operation under difficult underwater conditions and outperforms existing alginate-based solutions in terms of wet strength, long-term cell suitability and stability. Based on rheological investigations, the critical strength of moist TCNF matrices is three times higher than that of the existing immobilization matrices of alginate cross-linked with Ca2+. This is due to the rigid nature of the colloidal nanofiber network and the strong cross-linking with PVA as opposed to polymeric alginate with reversible ionic Ca2+ Tie up. The porous and hygroscopic nanofiber network also protects the cyanobacterial cells from environmental stress and maintains photosynthetic activity during the partial drying of films and when immersed in the nutrient medium for long-term cultivation. Finally, TCNF matrices enable the production of ethylene Synechocystis sp. PCC 6803 cells operate under submerged conditions with high inorganic carbon loads (200 mM NaHCO)3), where approx.2+-Alginate matrices fail. The latter already show severe cell leakage within 20 minutes after NaHCO due to the disintegration of the matrix3 Complement. In contrast, TCNF-based matrices prevent cells from leaking into the medium and limit culture growth, resulting in improved ethylene production yields. In addition, the operating capacity of the independent TNCF cell factory can be maintained in the long term by periodically refreshing the nutrient medium. All in all, the results show the versatility and potential of cell immobilization with the never-dried colloidal TCNF matrix and pave the way for novel biotechnological avenues using solid-state cell factories designed for efficient and sustainable production of cells e.g., Monomers and fuels.

Graphic summary: Mechanically stable immobilization matrix based on nanocellulose for improved ethylene production: a framework for photosynthetic solid-state cell factories

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