Precise Determination of Lignin in Residue Obtained from Enzymatic Hydrolysis of Phyllostachys pubescens Stem Alkaline Sulfite Pulp

摘要

Previous research has shown that bamboo stem alkaline sulfite pulp is enzymatically hydrolyzed with a much greater enzymatic saccharification ratio than larch pulp and cellulose filter paper. In order to investigate the residual lignin and saccharification behavior of pulp during enzymatic hydrolysis, it is necessary to precisely determine the lignin content of the pulp after enzymatic hydrolysis. To investigate the behavior during enzy- matic hydrolysis and the residual lignin of these pulps, methods that can precisely determine the lignin content after enzymatic hydrolysis were considered. One of the widely used methods for determining lignin content is the acetyl bromide method, by which it was shown that the xylan in bamboo pulp affected the determination of the residual lignin due to the UV absorption by the reaction products. Furthermore, the amount of water in the reaction system also affected the UV absorbance. The application of the acetyl bromide method to bamboo alka- line pulp is difficult. On the other hand, using a pyrolysis-gas chromatography/mass spectrometry method, the lignin content of the pulp after enzymatic hydrolysis can be precisely estimated. It was shown that bamboo alkaline sulfite and soda pulps produced much more glucose than cellulose filter paper during enzymatic hydrolysis, and the residue ratios were found to be low. The determination of the lignin content of the residue after enzymatic hydrolysis showed that the lignin content decreased as the enzymatic hy- drolysis of the pulp proceeded. Conversely, the lignin content of the soda pulp during enzymatic hydrolysis was almost constant. It was also suggested that lignin dissolved from bamboo pulp during the enzymatic hydrolysis enhanced the enzymatic saccharification ratio.