(149a) Innovative Feedstock Design through Repartition of Photosynthetic Carbon to Terpene Production

Photosynthetic terpene production efficiently transforms sunlight energy for reducing inorganic carbon and represents one of the most carbon efficient route for hydrocarbon production from CO₂. Despite the advantages, enhancing photosynthetic terpene production has been highly challenging. We have systemically designed alternative pathways to repartition photosynthetic carbon into terpene biosynthesis to enhance productivity. First, we have identified the key metabolic bottleneck for limonene production in the cyanobacterium Synechococcus elongates and achieved >100 fold increase in limonene productivity. The engineered strains allowed us to discover sucrose accumulation at low limonene productivity stage. Further engineering of sugar metabolisms have enabled the repartition of carbon from sugar metabolism to terpene metabolism to enhance limonene production to a higher level. Second, we have designed C2 redirection pathway to channel photorespiratory glycolate to pyruvate and subsequently terpene biosynthesis in tobacco using squalene as a model terpene. The study suggested that a functional C2 redirection could increase terpene yield without significantly impacting photosynthetic carbon fixation. Metabolomics analysis revealed a significant carbon repartition, as a decrease in the intermediates of sucrose and starch biosynthesis correlated with an increase in malate and pyruvate in the C2 redirection lines. Third, we have developed a C5 redirection pathway to channel carbon directly from Calvin Benson cycle to terpene biosynthesis and by-pass the speed-limiting step. The strategy has successfully achieved increased terpene productivity and carbon repartition. Overall, we have established repartition of photosynthetic carbon from sugar metabolism to terpene metabolism as an efficient approach for enhancing hydrocarbon yield in plants and cyanobacteria.