*2.6. Analytical Methods*

Monomeric carbohydrates in the hydrolysates were determined by borate–anion exchange chromatography (borate–AEC) with a DionexTM UltiMateTM 3000 (Thermo Fisher ScientificTM, Waltham, MA, USA) and MCI GEL® CA08F (Mitsubishi Chemical, Tokio, Japan) as anion exchange resin. Two potassium tetraborate/boric acid-buffers (pH 8.6 and pH 9.5) were used in different concentrations as mobile phase after post-column derivation at 65 ◦C. Carbohydrates were detected at 560 nm via UV/VIS-spectroscopy. More detailed information about the used borate–AEC was reported by Lorenz et al. [27].

For detection of furfural and 5-hydroxymethylfurfural, reversed phase-high-performance liquid chromatography (RP-HPLC) separation was performed with an AQUASILTM C<sup>18</sup> (250 × 4.6 mm; Thermo Fisher ScientificTM, Waltham, MA, USA) column for 80 min with 10 µL extract at 25 ◦C. As a mobile phase, weak acidic water (A; 1 mM H3PO4) and acetonitrile (B; C2H3N) were used as eluents in different concentrations and a flow rate of 1 mL/min like shown in Table 2. The detection was conducted at 280 nm.


**Table 2.** Concentrations of the two eluents over time during RP-HPLC.

Size exclusion chromatography (SEC) was performed according to Podschun et al. [30] with a mixture of DMSO and 0.1% LiBr as eluent. One guard PolarGel-M column (50 × 7.5 mm; Agilent, Santa Clara, CA, USA) and two PolarGel-M columns (300 × 7.5 mm; Agilent, Santa Clara, CA, USA) were used with a flow rate of 0.5 mL/min−<sup>1</sup> at 60 ◦C. Glucose and polyethylene glycol were used as standards with a refractive index detector (RI-501, ShodexTM, Munich, Germany). The dissolved samples (*c* = 1 mg/mL−<sup>1</sup> ) were shaken for 24 h at room temperature into the eluent. The sample detection was made with a UV-2077 detector (JASCO, Pfungstadt, Germany) at 280 nm and phenol red as detector matching.
