Fourier transform infrared spectroscopy (FTIR) (8400S Shimadzu, Japan) was used for investigating the changes in surface functional groups of the samples, before and after microbial decolorization. FTIR analysis was done in the mid-IR
region of 400e4000 cm1 with 16 scan speed.
The pellets were prepared using spectroscopic pure KBr (5:95, w/w) and fixed in the sample holder for analyses. The
identification of metabolites formed after degradation was carried using a QP2010 gas chromatography (GC) coupled with mass spectroscopy (MS) (Shimadzu).
The ionization voltage was 70 eV. GC was conducted in the temperature programming mode with a Restek column (0.25 mm, 60 m; XTI-5). The initial column temperature was 80C for 2 min, then increased linearly at 10C/min to 280C, and held for 7 min.
The temperature of the injection port was 280C, and the GCeMS interface was maintained at 290C. The helium carrier gas flow rate was 1.0 ml/min. Degradation products were identified by comparison of retention time and fragmentation pattern, as well as with mass spectra in the NIST spectral library stored in the computer software (version 1.10 beta, Shimadzu) of the GCeMS.