Decoding key genes of Pseudomonas sp. HNGD-T31 involved in citrus flavor (+)-valencene biotransformation to (+)-nootkatone by integrated genomics and transcriptomics

(+)-Nootkatone is a sesquiterpene compound with persistent and strong citrus fruit aroma, which plays an important role in food, medicine and agriculture fields. A new strain of Pseudomonas sp. HNGD-T31 (CCTCCM 20251583) was isolated from citrus reticulata regional soil and proved to be able to transform (+)-valencene to (+)-nootkatone in this study. The highest yield of (+)-nootkatone (418.31±1.83 mg/L) was obtained when Pseudomonas sp. HNGD-T31 was incubated for 48 h at 36°C and 200 rpm, and the biotransformation process was monitored for 36 h after adding 920 mg/L (+)-valencene/DMSO (0.8% (v/v)). The genome of Pseudomonas sp. HNGD-T31 comprised approximately 5.92 Mb with 5255 predicted protein-coding genes, and the comparison of P_V_36h versus P_36h revealed 334 differentially expressed genes (DEGs), many of which exhibited significant regulation. These DEGs were involved in ABC transporter, energy metabolism, secondary metabolism, carbohydrate metabolism, amino acid metabolism and responsible for converting (+)-valencene into (+)-nootkatone. This study provided a new strain for (+)-nootkatone production and the molecular mechanisms involved in producing (+)-nootkatone by biotransformation.