Abstract:

In order to effectively utilize the cellulose and hemicellulose existing in paper sludge,the basic characteristics of Clostridium thermocellum ( C. thermocellum) cultured in different substrates,especially in unpretreated paper sludge,were discussed,and the corresponding cellulase and xylanase were also investigated. The results show that C. thermocellum is a potential strain for combined bioprocessing because it can directly ferment paper sludge without any pretreatment,and that,when chemical paper sludge is used as the substrate for C. thermocellum,the yield of ethanol reaches 7. 41 g /L,which is 1. 779 times that of the ethanol obtained from using commercial cellulose as the substrate,and the cellulase and xylanase activities reach 1. 92 U/mL and 1. 30 U/mL,respectively. However,in recycled paper sludge,the ethanol yield decreases to 1. 31 g /L because the fermentation is inhibited,and the cellulase and xylanase activities are respectively 1. 64U/mL and 0. 90U/mL. Moreover,it is found that the optimal temperature and pH value for cellulase are 60℃ and 5. 5,respectively,while those for xylanase are respectively 70℃ and 7. 0,and that both cellulase and xylanase possess strong adaptability to metal ions.

Key words: Clostridium thermocellum, paper sludge, fuel ethanol, cellulase, xylanase