Aoc 20

The chemical structure of the PEI treatment of polypropylene fabrics was characterized using a Fourier-transform infrared (FT-IR) spectrophotometer (Nicolet iS5, Thermo Fisher Scientific., Waltham, MA, USA) equipped with an attenuated total reflection accessory (iD7 ATR, Thermo Fisher Scientific., Waltham, MA, USA). The surface morphologies of both untreated and PEI-treated polypropylene fabrics were observed using a field emission scanning electron microscope (FE-SEM, SU8220, Hitachi, Tokyo, Japan). All samples used for FE-SEM were coated with platinum to improve conductivity before the SEM observation. The X-ray photoelectron spectroscopy (XPS) spectra were obtained using an X-ray photoelectron spectrometer (NEXSA, Thermo Fisher Scientific., Waltham, MA, USA) with a monochromatized Al–Kα source and X-ray spot size of 100 μm. The extracted mixture of DFP and DHP after the hydrolysis reaction of DFP was analyzed via GC (GC-2030, Shimadzu, Kyoto, Japan) with an Elite-1 column (dimethylpolysiloxane, 30 m, 0.25 mm, I.D., 0.25 µm, PerkinElmer) and autosampler (AOC-20, Shimadzu, Kyoto, Japan) to achieve a reliable quantitative analysis.

Lipids from milk and Chanco-style cheese samples were extracted according to the method proposed by [25 (link)] and the methylation was performed according to the Christie protocol [26 (link)] with modifications by [27 (link)]. Then a gas chromatography system (Shimadzu Scientific Instruments AOC-20, Columbia, MD, USA) equipped with a 100 m column with the following chromatographic conditions was used: after the injection, the oven temperature was set at 110 °C for 4 min and after that it was raised to 160 °C at a rate of 5 °C/min for 10 min, then to 225 °C at a rate of 3 °C/min for 10 more minutes and finally increased to 240 °C at a rate of 3 °C/min. The temperature of the ionization flame was 260 °C, the injection volume 2 μL, the hydrogen flow 25 mL/min, the airflow 400 mL/min and the flow of nitrogen that makes up the gas was 40 mL/min. The fatty acid peaks in the gas chromatograph were identified using standardization methyl esters of fatty acids (FAME, Supelco 37 Component FAME mix, Bellefonte, PA, USA). Retention times were compared with those from similar studies focused on Chanco-style cheese FA profile [15 (link),19 (link)].

Total intracellular lipid contents were estimated as total fatty acids. Accumulated lipids were extracted from lyophilized cells using a hydrochloric acid-catalyzed direct methylation method [31 (link)]. In brief, after cultivation, the centrifuged cells were lyophilized and weighed, dissolved in toluene and methanol, and directly transmethylated with 8% (v/v) methanolic HCl at 100°C for 1 h. The resultant fatty acid methyl esters were extracted with n-hexane and analyzed using a gas chromatograph (GC-2010 Plus; Shimadzu, Kyoto, Japan) equipped with a flame ionization detector (FID) and an autosampler (AOC20; Shimadzu). A TC-17 capillary column (GL Science, Tokyo, Japan) was used. The elution temperature commenced at 165°C for 2 min and then increased by 5°C/min to 180°C, followed by a hold for 5 min, an increase at 5°C/min to 240°C, and an additional hold for 3 min. Helium at 2.0 mL/min served as the carrier gas, and nitrogen as the make-up gas. The injector temperature was 250°C and the detector temperature was 260°C, with a split ratio of 50:1. Major peaks were identified by their retention times using standards obtained from Sigma-Aldrich (St. Louis, MO, USA). Heptadecanoic acid (C17:0) served as an internal standard for the determination of fatty acid concentrations.