Material-Dependent, Agitation-Free Fermentation on 3D-Printed Polymer Matrices: Lactic Acid Bacteria Surpass Shaken Cultures

Abstract

Industrial fermentation relies on mechanically agitated submerged culture, in which impeller-driven mixing improves oxygen and nutrient transfer but imposes an energy penalty and a hydrodynamic shear field that stresses cells. Solid supports offer an agitation-free alternative, yet their surface is typically ill-defined and only a single polymer and a single organism have been examined. Here we treat the support material as a controllable process variable. Using an identical scaffold geometry 3D-printed by fused-deposition modeling in four thermoplastics—ABS, TPU, PLA, and PETG—we compared static cultivation of a model yeast (Saccharomyces cerevisiae) and a model lactic acid bacterium (Lactobacillus plantarum) against shaken and static controls, and related the outcomes to polymer surface wettability. For S. cerevisiae, embedding a matrix in static medium nearly doubled biomass relative to the static control and drove glucose to near-complete assimilation, raising ethanol titres ~1.7–1.8-fold to shaken-culture levels without any agitation. For L. plantarum, three of the four matrices (PLA, ABS, PETG) exceeded both the static and the aerated shaking controls in biomass (by ~15–21%) and in lactic acid production, while the elastomeric TPU behaved like the controls. Because L. plantarum is microaerophilic, these results suggest that factors other than improved aeration, including interactions at the scaffold–liquid interface, contribute to the observed enhancement. The polymer type thus emerges as a tunable parameter for scaffold-assisted cultivation, enabling fermentation without mechanical agitation while achieving performance comparable to, and in some cases greater than, that of shaken culture. The polymer type thus emerges as a tunable determinant of performance, defining an agitation-free cultivation strategy in which the interface—rather than bulk flow—is engineered to achieve, and in some cases surpass, the productivity of conventional stirred culture.