Modular artificial photosynthetic microbial consortium for the CO2-driven production of cis, cis-muconate

Abstract

With the increasing restrictions on petrochemical-derived polymers and growing demand for sustainable materials, cis, cis-muconate (ccMA) has emerged in recent years as a promising platform chemical for green manufacturing. However, ccMA biosynthesis in heterotrophic microorganisms still consumes sugar- or lignin-derived feedstocks, which constrains its sustainability profile and prevents it from being a truly green or carbon-negative process. Although photosynthetic microorganisms can be engineered as “negative-carbon factories” to convert photosynthetically fixed CO2 into diverse value-added products, the direct synthesis of ccMA has so far been precluded by intrinsic metabolic limitations, including the feedback-regulated and largely unexplored shikimate pathway as well as an NADPH/ATP imbalance that conflicts with high NADPH demand of ccMA biosynthesis. This study presents a two-species, three-module design for sustainable ccMA biomanufacturing. Specifically, a model photosynthetic chassis Synechococcus elongatus PCC 7942 was engineered with sucrose and trans-cinnamic acid module to supply carbon and engery, while the heterophic chassis Corynebacterium glutamicum ATCC 13032 carried a reonstructed shikimate module for ccMA synthesis. This modular distribution not only alleviated metabolic burden in individual strains but also enhanced system robustness through rational medium optimization, fine-tuned inoculation ratios, and spatial stabilization of cyanobacteria using sodium alginate hydrogel immobilization. While the titers remain modest (7.04 and 8.61 mg L⁻1 under non-immobilization and immobilization, respectively), this proof-of-concept system achieved a net carbon reduction of −15.10 kg CO2e kg-1 of produced ccMA, highlighting its environmental advantages and potential for carbon-negative biomanufacturing.