The BS protein content was determined by the method of Bradford28 (link) applying Coomassie brilliant blue with bovine serum albumin as a standard. Carbohydrate content was estimated by the phenol-sulfuric acid procedure of Dubois29 (link) using D-glucose as a standard, and lipid content was determined by the method of Folch et al.30 (link). The fatty acids of the BS were converted to their methyl esters (FAMEs), then analyzed in a gas chromatograph (Thermo Finnigan, USA) equipped with a split/splitless injector, a fused silica CP-Sil 88 capillary column (length 100 m × 0.25 mm internal diameter with 0.25 μm film thickness) and a flame ionization detector (FID). The injector temperature of 250 °C was applied for the injection of the 1 μl samples. The column temperature was programmed to be between 140 and 240 °C at a rate of 3.2 °C/min. Nitrogen gas was used as the carrier gas. The FID temperature was kept at 260 °C during the analysis. The fatty acids were identified by comparing the retention times of the methyl esters of the samples with the standard.
Also, the Fourier transforms infrared (FTIR) spectra of the lyophilized samples of the BSs produced by P. dextrinicus SHU1593 were taken in the wavelength range of 400–4000 cm−1 with a scan speed of 2 mm/s on an FTIR system (Perkin-Elmer Spectrum RX I, USA).
Also, the Fourier transforms infrared (FTIR) spectra of the lyophilized samples of the BSs produced by P. dextrinicus SHU1593 were taken in the wavelength range of 400–4000 cm−1 with a scan speed of 2 mm/s on an FTIR system (Perkin-Elmer Spectrum RX I, USA).