Hemicellulose influence on cellulose enzymatic conversion of three surgarcane hybrids

Considering that the hemicellulose hinders the cellulases accessibility to cellulose chains, we determined the influence of this material in the cellulose enzymatic hydrolysis from three sugarcane hybrids with originally contrasting chemical compositions. The hybrids were treated with dilute sulfuric acid (13 g/100g of bagasse) at 150 ^oC for 20 to 90 min. Treated samples that presented varied hemicellulose contents (31.0-4.8%) were enzymatically hydrolyzed in the presence or absence of albumin. Cellulose conversion efficiency ranged from 13% to 63%. The albumin positive effect was observed only for samples pretreated at severe conditions. Linear correlations between residual hemicellulose contents (and removal levels) and the cellulose conversion yields were observed (R² values near to 0.99). The samples pretreated for 90 min were further delignified with aqueous acetic acid/chlorite to evaluate if lignin removal could increase the cellulose conversion yields. Chlorite delignification resulted in cellulose conversions increased by 20 percentage points. When data from all pretreated samples were grouped, the cellulose conversion levels correlated with the accessible cellulose contents in the samples. Accessible cellulose was defined as the cellulose contents divided by the sum of hemicellulose plus lignin. Data showed that the hemicellulose contents influenced the cellulose conversion yields and that this effect varied among the evaluated hybrids. The accessible cellulose contents proved to be an interesting parameter to predict cellulose conversion yields, since it fit well even to data obtained from samples that were treated by two different process and originally exhibited contrasting chemical compositions.