The concentrations of (−)-α-bisabolol were determined based on previously described methods (18 (link)). In brief, n-dodecane was overlaid in the culture medium to extract (−)-α-bisabolol produced from E. coli. After cultivation, the n-dodecane layer was recovered by centrifugation at 14,500 × g for 3 min. The (−)-α-bisabolol amount extracted in the n-dodecane layer was determined using a gas chromatography (7890B, Agilent, SC, USA) system equipped with a flame ionization detector (FID) with an HP-5 column (30 m x 0.320 mm x 0.25 μm) and a flow rate of 1 ml/min. The starting temperature of the oven was 60°C for 2 min. This was increased by 5°C/min to 200°C, held at 200°C for 2 min, raised by 50°C/min to 300°C, and held at 300°C for 5 min. The concentrations of (−)-α-bisabolol (Sigma-Aldrich) were used to generate a standard curve.