Cell immobilization on 3D-printed matrices: A model study on propionic acid fermentation.

This study uses three-dimensional (3D) printing technology as a tool for designing carriers for immobilization of microbial cells for bioprocesses. Production of propionic acid from glucose by immobilized Propionibacterium sp. cells was studied as a model system. For cell adsorption, the 3D-printed nylon beads were added to the culture medium during 3 rounds of cell cultivation. Cell adsorption and fermentation kinetics were similar irrespective of the bead size and lattice structure. The cells bound to 15 mm beads exhibited reduced fermentation time as compared to free cell fermentations; maximum productivity and propionic acid titer of 0.46 g/L h and 25.8 g/L, respectively, were obtained. Treatment of the beads with polyethyleneimine improved cell-matrix binding, but lowered the productivity perhaps due to inhibitory effect of the polycation. Scanning electron micrographs revealed the cells to be located in crevices of the beads, but were more uniformly distributed on PEI-coated carrier indicating charge-charge interaction.