Systematic engineering to enhance valencene production in Rhodobacter sphaeroides

Abstract

Microbial synthesis of (+)-valencene from agricultural wastes such as cornstalk will serve as a sustainable alternative to the traditional plant extraction method. In this study, Rhodobacter sphaeroides strains were engineered for valencene production through a stepwise manner: (1) heterologous expression of Callitropsis nootkatensis valencene synthase (CnVS) in combination with phaB/gdhA/ladH knockouts enabled de novo biosynthesis of valencene from glucose at a titer of 34.21 ± 3.1 mg/L; (2) a quorum-sensing promoter P_cer to decouple growth and production phase further improved the valencene titer to 80.75 ± 3.0 mg/L; and (3) transposon-mediated genomic integration of the heterologous mevalonate pathway to enhance farnesyl pyrophosphate supply resulted in 120.53 ± 10.34 mg/L valencene. Subsequently, the alkali-pretreated cornstalk hydrolysate was used as the substrate, and 100.51 ± 14.15 mg/L valencene was achieved under the optimized carbon-to-nitrogen ratio. In summary, the engineered R. sphaeroides offers an alternative mean to valorize the cheap agricultural waste for high-value valencene production.

Keywords

Rhodobacter sphaeroides / Valencene / Metabolic engineering / Process optimization / Agricultural waste

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Funding

National Key Research and Development Program of the Ministry of Science and Technology(2024YFC3407000)

Natural Science Foundation of Xiamen, China(3502Z202471013)

National Natural Science Foundation of China(32270087)

Fundamental Research Funds for the Central Universities(20720240120)

RIGHTS & PERMISSIONS

The Author(s)