J 1500 cd

The cultures were collected over the growth phases and then filtered using 0.22-µm membrane filters (Millipore, USA), and the supernatants were stored at −20°C. The concentration of D-Glu was determined by a circular dichroism analyzer CD J-1500 (Jasco, Tokyo, Japan) as previously described (73 (link)) with slight modifications. Briefly, the scan rate and band width of the instrument were set to 50 nm/min and 1.0 nm, respectively. The spectra were recorded between 200 and 220 nm using 0.1-nm carving, and an average of the three scanning values was taken. The CD spectrum between 205 and 215 nm was chosen for integration, and the integrated value ( $\sum \theta$ ) was plotted against the given D-Glu concentration. The fitted standard curve was y ( $\sum \theta$ ) = −4,145.9 × (D-Glu concentration) + 16.04 (R² = 1).

On the basis of the previous report with slightly modification (Jiang et al., 2014), circular dichroism (CD) spectropolarimetry was scanned at the far‐UV range (260–180 nm) in order to reveal the secondary structure of BMOP. BMOP (40 mg/ml) were centrifuged at 8,000 × g for 15 min at 25°C. The supernatants (3 ml) were used for circular dichroism spectropolarimetry measurements (CD‐J1500; Jasco International, Tokyo, Japan). Secondary structures including α‐helix, β‐sheet, β‐turn, and random coil were calculated using Spectra Manager Software (Jasco International).

Shimadzu UV-visible spectrometer UV-2600 (Shimadzu Corporation, Kyoto, Japan) was used to perform the UV-visible absorption studies using 1.0 cm quartz cuvettes. Fluorolog FL-221 spectrofluorimeter (HORIBA Jobin Yvon, Kyoto, Japan) was employed to perform fluorescence spectroscopic experiments using 1.0 cm quartz cuvettes. The CD spectra were recorded on a J-1500 CD (Jasco, Tokyo, Japan) spectrophotometer equipped with a Peltier temperature controller maintained at 25 °C, using a quartz cuvette of path length 1.0 cm.