Abstract: The degradation conditions of soybean straw lignin by Phanerochaete chrysosporium fermentation were studied in this paper. The results showed that addition of 5 g of soybean straw power to 12 mL of synthetic medium for fermentation at an initial pH of 4.5 and an inoculum size of 0.8 mL (8.6 × 106 CFU/mL spore suspension concentration) for 10 d proved optimal and the resultant degradation rate of lignin was 45.96%. Also, Fourier transform infrared spectroscopy (FTIR) was employed to changes in functional groups arising from lignin degradation. The results showed that the relative intensity of spectral peaks associated with lignin (1099cm-1and 1057-1038 cm-1) was weakened, whereas the relative intensity of spectral peaks associated with benzene (1643-1608 cm-1 and 1510-1508 cm-1) was enhanced. These results suggest the degradation of lignin into small molecules or lignin monomers. Moreover, the contents of benzene and cyclic compounds in lignin were decreased according to comparisons with the changes of other spectral peaks.

Key words: soybean straw, Phanerochaete chrysosporium Burdsall, lignin, FTIR