Abstract

The purpose of the present work was to evaluate the possibility of converting paper sludge into ethanol using xylose-fermenting yeast SHY07-1 in separate hydrolysis and fermentation. In the enzymatic hydrolysis step, sludge on 2% (w/v, expressed in terms of total carbohydrate mass) substrate consistency was incubated with the filter-sterilized enzyme solutions (Celluclast 1.5 L on a dosage of 15 FPU/g cellulose and Novozyme™188 on a dosage of 30 CBU/g cellulose) without any pretreatment, and a total degree of saccharification of 99.65% was achieved under certain conditions. The hydrolysate produced from enzymatically-digested paper sludge (on a consistency of 2% (w/v, expressed in terms of total carbohydrate mass) was fermented by yeast SHY07-1 without prior detoxification and nutrient supplementation, and xylose was consumed well. A final ethanol concentration of 14.18 g/L was achieved, corresponding to an ethanol yield of 0.49 g/g with a fermentation efficiency of 97.68%. The results indicate that paper sludge can be enzymatically hydrolyzed with high degree of saccharification and the hydrolysate can be fermented efficiently to ethanol by using xylose-fermenting yeast SHY07-1.

Key words: Paper sludge, separate hydrolysis and fermentation, ethanol, cellulase

Abbreviation

 PS, Paper sludge; SHF, separate hydrolysis and fermentation;HPLC, high-performance liquid chromatography; DS, degree of saccharification;FPU, filter paper units; CBU, cellobiohydrase units; SSF, simultaneous saccharification and fermentation.