Abstract:

Primary sludge from a toilet paper mill was used as biomass material to produce fuel ethanol via simulta- neous saeeharifieation and fermentation （SSF）, and three different non-ionic surfaetants, i.e. , Tween-20, Tween-60 and Tween-80, were evaluated for their ability to enhance SSF. The SSF process conditions were then optimized at a temperature of 36 ℃, with a substrate mass concentration of 100 g/L, an inoculums size of 6% （volume fraction）, and a cellulase dosage of 25 FPU/g. The results show that Tween-20 significantly accelerates the ethanol production. Specifically, the ethanol yield increases by 14% with a Tween-20 dosage of 0.2%. In the optimal conditions, the mass concentration of ethanol reaches 19.5 g/L after a 48 h incubation, which is 63.9% of the theoretical one. An analysis of the main chemical compositions of the paper sludge before and after SSF and of the fermentation liquor shows that a large amount of cellulose is converted into ethanol and only a small amount of hemicellulose is hydrolyzed, and that the hydrolysate xylose cannot be effectively used by yeast for ethanol production. Moreover, SEM results indicate that, after SSF, the long linear fibers in the paper sludge are destroyed and a lot of ellipsoidal yeast cells appear simultaneously.

Key words: paper sludge, cellulase, Saccharomyces cerevisiae, ethanol, surfactant