Extended toolboxes enable efficient biosynthesis of valuable chemicals directly from CO2 in fast-growing Synechococcus sp. PCC 11901

CO2 recycle is crucial to the global carbon neutrality. Though cyanobacteria are known to be photoautotrophic cell factories capable of converting CO2 into valuable chemicals, their slower growth rate and lower biomass accumulation compared to those of the heterotrophic organisms significantly restrict their application at commercial scale. The newly discovered marine cyanobacterium, Synechococcus sp. PCC 11901 (hereafter PCC 11901) offers several advantages like rapid growth, high biomass and high salinity tolerance, and could become a new generation of cyanobacterial chassis. To promote its application, in this study we developed genetic toolboxes applicable to PCC11901. First, a cobalamin (VB12)-independent chassis was constructed, allowing for its cheaper cultivation. Second, genome copy numbers and transformation methods were respectively measured and optimized. The 14 neutral sites were identified and characterized within the genome PCC 11901, providing locations for genetic integration of exogenous cassettes. Subsequently, libraries were developed, reaching an expression range of approximately 800 folds for constitutive promoters and an induction fold of up to approximately 400 for inducible promotor, respectively. As a proof of concept of its utilization, we engineered the synthetic pathways of glucosylglycerol (GG) into PCC 11901 using the established toolboxes, yielding 590.41 {+/-} 21.48 mg/L for GG production. Notably, we found the cobalamin-independent PCC 11901 chassis exhibited superior self-sedimentation ability compared to the wild-type chassis. Our work here made it possible to develop the fast-growing PCC 11901 as efficient carbon-neutral cell factory in the future.