*2.4. Fourier-Transform Infrared Spectroscopy Analysis*

The functional group analysis of the untreated or pretreated SSB and CC biomass samples was analysed with Fourier Transform Infrared (FTIR) Spectroscopy. The FTIR spectra of Avicel (cellulose control), untreated, Ca(OH)<sup>2</sup> and NaOH pretreated SSB and CC samples were recorded at room temperature using an UATR-FTIR instrument (PerkinElmer, USA). All FTIR spectra were collected at a spectrum resolution of 4 cm−<sup>1</sup> , with 4 co-added scans per sample over the range of 4000 to 650 cm−<sup>1</sup> . The Perkin-Elmer software (Spectrum version. 6.3.5) was used to perform spectra normalisation, baseline corrections, and peak integration. The spectra of the Avicel PH101 microcrystalline cellulose, untreated, pretreated SSB and CC samples were presented as absorbance values, and each value represented the means of four scans.
