Using lime pretreatment to facilitate the enzymic hydrolysis of corn stover

Corn stover is an abundant, potential fermentation substrate. The most effi cient means to produce fermentable sugars from corn stover is by enzymic hy drolysis, which is facilitated by thermochemical pretreatment of the corn s tover. Pretreatment with slake lime (calcium hydroxide) increased the enzym ic hydrolysis of corn stover nine times compared to untreated corn stover. The recommended pretreatment conditions are: lime loading 0.075 g Ca(OH)(2) (g dry biomass)(-1); water loading 5 g H2O (g dry biomass)(-1;) and heatin g for 4 h at 120 degrees C. The recommended enzyme loading for the enzymic saccharification of pretreated corn stover is 10 FPU (g dry biomass)(-1) an d the recommended hydrolysis temperature is 40 degrees C. The enzymic conve rsion of the corn stover to monosaccharides, when pretreated and saccharifi ed as prescribed for 72 h, was about 60% cellulose, 47% xylan, and 53% tota l available polysaccharide. Increasing the enzyme loading to 25 FPU (g dry biomass)(-1) and the hydrolysis time to 7 days produced conversions of 88.0 , 87.7, and 92.1% for the glucan, xylan and arabinan, respectively. These h igh conversions indicate that pretreatment with lime can lead to corn stove r polysaccharide conversions approaching 100%; the success of the saccharif ication after lime pretreatment depends on the enzyme loading. (C) 2000 Els evier Science Ltd. All rights reserved.