PEARL: Protein Eluting Alginate with Recombinant Lactobacilli

Abstract Engineered living materials (ELMs) made of bacteria in hydrogels have shown considerable promise for therapeutic applications through controlled and sustained release of complex biopharmaceuticals at low costs and with reduced wastage. While most therapeutic ELMs use E. coli due to its large genetic toolbox, most live biotherapeutic bacteria in development are lactic acid bacteria due to native health benefits they offer. Among these, lactobacilli form the largest family of probiotics with therapeutic potential in almost all sites of the body with a microbiome. A major factor limiting the use of lactobacilli in ELMs is their limited genetic toolbox. This study expands on recent work to expand the genetic programmability of probiotic Lactiplantibacillus plantarum WCFS1 for protein secretion and encapsulate it in a simple, cost‐effective, and biocompatible core–shell alginate bead to develop an ELM. The controlled release of recombinant proteins is demonstrated, even up to 14 days from this ELM, thereby terming it PEARL – Protein Eluting Alginate with Recombinant Lactobacilli. Notably, lactobacillus encapsulation offered benefits like bacterial containment, protein release profile stabilization, and metabolite‐induced cytotoxicity prevention. These findings demonstrate the mutual benefits of combining recombinant lactobacilli with alginate for the controlled and sustained release of proteins.