3D Bioprinting Enzyme-Bacteria Symbionts for Lactic Acid Production from Cellulose Bioconversion

Bioconversion of waste cellulosic biomass into high-value chemicals holds significant potential, although traditional cocultures face challenges such as microbial competition and poor spatial organization, which limit stability and efficiency. Herein, we, for the first time, created enzyme-bacteria symbionts with customized geometric configurations using a three-dimensional (3D) bioprinting platform for efficient lactic acid production from cellulose. To facilitate 3D printing, a biocompatible and tunable dual-network functional living bioink was developed with optimized rheological properties, enabling meticulous manipulation of the spatial arrangement and density of active components. By optimizing spatial niches, the design featuring an inner cellulase layer and an outer bacteria layer improved lactic acid production efficiency during cellulose bioconversion. At an optimal enzyme loading of 35 U/mL, the maximum lactic acid yield of 6.55 ± 0.34 g/L was achieved using 3D-bioprinted symbionts with 17.5 g/L cellulose as the sole carbon source. Importantly, reaction-diffusion simulations clearly revealed the spatial and radial distributions of the intermediate product glucose and the final product lactic acid within the enzyme-bacteria symbionts. This work establishes a new design paradigm for engineered living materials, providing a scalable platform for diverse waste-to-product conversions and practical pathways for implementing circular bioeconomy principles.