Engineering orthogonal and synergistic modules in marine bacteria for efficient upcycling of lignin-derived carbon

Rational allocation of cellular carbon between engineered behaviors and essential metabolic activities is a longstanding challenge in engineering microbes with unusual competencies. Here, we established orthogonal-yet-synergistic modules in marine bacteria to leverage their unique metabolic potential for upcycling lignin-derived carbon into valuable chemicals. First, we determined the superior catalytic capability of Roseovarius nubinhibens to circumvent the biological constraint in the essential metabolic node. Then, we genetically decoupled biosynthesis pathway from central metabolism to channel the lignin-derived monomer into products, utilizing acetate to sustain cell growth and supply necessary resources, but not substrates, for biosynthesis. Besides this designed division of labor, we identified a cross-module push-and-pull synergy between biosynthesis and cell growth. By deploying this biological scheme, we successfully achieved escalated conversion of the lignin-derived monomer 4-hydroxybenzoate to pharmaceutical compound protocatechuate with seawater, rather than freshwater, as the water source, underscoring its potential in concurrent carbon and water conservation.