Using lime pretreatment to facilitate the enzymic hydrolysis of corn stover

Corn stover is an abundant, potential fermentation substrate. The most efficient means to produce fermentable sugars from corn stover is by enzymic hydrolysis, which is facilitated by thermochemical pretreatment of the corn stover. Pretreatment with slake lime (calcium hydroxide) increased the enzymic 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 heating for 4 h at 120°C. The recommended enzyme loading for the enzymic saccharification of pretreated corn stover is 10 FPU (g dry biomass)−1 and the recommended hydrolysis temperature is 40°C. The enzymic conversion of the corn stover to monosaccharides, when pretreated and saccharified as prescribed for 72 h, was about 60% cellulose, 47% xylan, and 53% total 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 high conversions indicate that pretreatment with lime can lead to corn stover polysaccharide conversions approaching 100%; the success of the saccharification after lime pretreatment depends on the enzyme loading.