Direct Writing of Tunable Living Inks for Bioprocess Intensification

TLDR

Critical to the success of three‑dimensional printing of living materials with high performance is the development of new ink materials and 3D geometries that favor long‑term cell functionality. The study reports using freeze‑dried live cells as a solid filler to create a living material system for direct ink writing of catalytically active microorganisms with tunable densities and self‑supporting porous 3D geometries. The authors fabricate the material by freeze‑drying live cells into a solid filler that is then extruded as ink to produce porous 3D structures with controllable cell density. Printed yeast‑based inks exhibited high resolution, large scale, high catalytic activity, long‑term viability, unprecedented cell loading, thixotropic behavior, and increased ethanol production versus bulk due to improved mass transfer, showing a versatile platform for bioprocess intensification.

Abstract

Critical to the success of three-dimensional (3D) printing of living materials with high performance is the development of new ink materials and 3D geometries that favor long-term cell functionality. Here we report the use of freeze-dried live cells as the solid filler to enable a new living material system for direct ink writing of catalytically active microorganisms with tunable densities and various self-supporting porous 3D geometries. Baker's yeast was used as an exemplary live whole-cell biocatalyst, and the printed structures displayed high resolution, large scale, high catalytic activity and long-term viability. An unprecedented high cell loading was achieved, and cell inks showed unique thixotropic behavior. In the presence of glucose, printed bioscaffolds exhibited increased ethanol production compared to bulk counterparts due largely to improved mass transfer through engineered porous structures. The new living materials developed in this work could serve as a versatile platform for process intensification of an array of bioconversion processes utilizing diverse microbial biocatalysts for production of high-value products or bioremediation applications.