The molecular weight of EPS was obtained by matrix-assisted laser desorption/ionization/time-of-flight (MALDI TOF/TOF) analyzer equipped with a Nd:YAG 355-nm laser (Ultraflex III, Bruker) as described previously [34 (link)]. Mass spectra were recorded in positive reflector (range 1–10 KDa) and lineal (range 1–20 KDa) modes, using a matrix of 10 mg/mL 2,5-dihydroxibenzoic acid (DHB) in methanol/water (90/10).
Gas chromatography (EVOQ GC–TQ, Bruker) coupled with a mass spectrometry detector (GC-MS) was used to determine monosaccharides following the procedure described in the literature [37 (link)]. EPS was hydrolyzed at 120 °C for 2 h with 0.5 M trifluoroacetic acid (TFA). A 1 μL sample with source temperature of 230 °C was injected into the capillary column (30 m × 0.250 mm) and gas helium (1 mL/min). Glucose, arabinose, rhamnose, xylose, mannose, galactose, fructose and sorbose were used as standard. HPLC–MS/MS using an Agilent Technologies 1100 series was used for the determination of amino acids and glucuronic acid [38 (link)]. For this, the ACE Excel 3 C18-Amide column (stationary phase) and 0.1% formic acid in water (mobile phase) were used. Flow temperature was 0.2 mL/min at 40 °C.
Gas chromatography (EVOQ GC–TQ, Bruker) coupled with a mass spectrometry detector (GC-MS) was used to determine monosaccharides following the procedure described in the literature [37 (link)]. EPS was hydrolyzed at 120 °C for 2 h with 0.5 M trifluoroacetic acid (TFA). A 1 μL sample with source temperature of 230 °C was injected into the capillary column (30 m × 0.250 mm) and gas helium (1 mL/min). Glucose, arabinose, rhamnose, xylose, mannose, galactose, fructose and sorbose were used as standard. HPLC–MS/MS using an Agilent Technologies 1100 series was used for the determination of amino acids and glucuronic acid [38 (link)]. For this, the ACE Excel 3 C18-Amide column (stationary phase) and 0.1% formic acid in water (mobile phase) were used. Flow temperature was 0.2 mL/min at 40 °C.
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