Altered Carbon Partitioning Enhances CO2 to Terpene Conversion in Cyanobacteria

Man Li; Bin Long; Susie Y Dai; James W Golden; Xin Wang; Joshua S Yuan

doi:10.34133/2022/9897425

Altered Carbon Partitioning Enhances CO₂ to Terpene Conversion in Cyanobacteria

Biodes Res. 2022 Feb 7:2022:9897425. doi: 10.34133/2022/9897425. eCollection 2022.

Authors

Man Li^{1

2

3}, Bin Long², Susie Y Dai², James W Golden⁴, Xin Wang^{1

2

5}, Joshua S Yuan^{1

2}

Affiliations

¹ Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, Texas 77843, USA.
² Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77843, USA.
³ Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of ScienceChina.
⁴ Section of Molecular Biology, University of California San Diego, La Jolla, CA 92093, USA.
⁵ Department of Microbiology, Miami University, Oxford, Ohio 45056, USA.

Abstract

Photosynthetic terpene production represents one of the most carbon and energy-efficient routes for converting CO₂ into hydrocarbon. In photosynthetic organisms, metabolic engineering has led to limited success in enhancing terpene productivity, partially due to the low carbon partitioning. In this study, we employed systems biology analysis to reveal the strong competition for carbon substrates between primary metabolism (e.g., sucrose, glycogen, and protein synthesis) and terpene biosynthesis in Synechococcus elongatus PCC 7942. We then engineered key "source" and "sink" enzymes. The "source" limitation was overcome by knocking out either sucrose or glycogen biosynthesis to significantly enhance limonene production via altered carbon partitioning. Moreover, a fusion enzyme complex with geranyl diphosphate synthase (GPPS) and limonene synthase (LS) was designed to further improve pathway kinetics and substrate channeling. The synergy between "source" and "sink" achieved a limonene titer of 21.0 mg/L. Overall, the study demonstrates that balancing carbon flux between primary and secondary metabolism can be an effective approach to enhance terpene bioproduction in cyanobacteria. The design of "source" and "sink" synergy has significant potential in improving natural product yield in photosynthetic species.