Synthetic Modular Cyanobacterial Consortium Enables Carbon-Negative Production of Glycerol and Derivatives

Abstract

Cyanobacteria offer a direct route for converting solar energy and CO2 into valuable chemicals, yet the metabolic burden of complex heterologous pathways often limits their productivity and stability. Here, we present a modular co-culture strategy that uses glycerol as an efficient mediator metabolite to link cyanobacterial carbon fixation with downstream bioconversion. We first engineered Synechococcus elongatus UTEX 2973 (Syn2973) for high-level glycerol biosynthesis by optimizing synthase selection, eliminating competing pathways, and improving CO2-supply conditions, achieving a production of 14.53 g{middle dot}L-1. In parallel, we constructed glycerol conversion modules in Syn2973 and Gluconobacter oxydans enabling production of 1,3-propanediol (1,3-PDO), 3-hydroxypropionic acid, and dihydroxyacetone, with exogenous glycerol yielding up to 30.07 g{middle dot}L-1 1,3-PDO. Integrating the two modules resulted in a fully autotrophic co-culture that produced all three target chemicals directly from CO2, including semi-continuous 1,3-PDO production at 6.02 g{middle dot}L-1{middle dot}day-1, corresponding to a net carbon fixation efficiency of 3.43 kg CO2 eq/kg 1,3-PDO.