The FTIR spectra of rice straw after
The FTIR spectra of rice straw after 40 days fermentation are shown in Fig. 6. The band at 1161 cm−1 represented conjugated ester-based CO stretching vibration disappeared in A (control) and B (2) after 40 days fermentation, which indicated much lignin of HGS type had been biodegraded. The prominent peaks at 1323 cm−1 represent S ring and 5-substituted G of lignin, and CH vibration of cellulose. A strong increasing intensity at 1323 cm−1 band was recorded in B (2), D (8), E (16) and F (32) as the Cd concentration increased, which indicated the fracture of S and G lignin, or CHIR265 structure by ligninolytic enzymes was inhibited by Cd at these concentrations. The intensity at 2355 cm−1 of CN or CC increased significantly in the presence of Cd compared to that in A (control), indicating that the fracture of CH to formation of CN or CC was induced by Cd. The band at 1659 cm−1 was assigned to conjugated carbonyls which could be mainly attributed to the coumaryl ester group and its intensity in C (4) was almost with that in A (control). The band of 2900 cm−1 was assigned to the methyl or methylene functional groups of cellulose had no obvious difference among all groups, therefore it was speculated that cellulose degradation was inhibited by Cd at high concentrations was depended on the inhibition of the fracture of CH of cellulose. In sum, the result showed that Cd could to some extent inhibit lignocelluloses degradation, especially lignin and cellulose.