Tuesday, April 30, 2013
Exhibit Hall
Internodes of three sugar cane hybrids were dissected into four fractions to represent the regions varying from the pith to the outermost rind. The outermost fraction and the rind were the most recalcitrant regions, whereas the pith was less recalcitrant. An inversely proportional correlation was observed between the area occupied by the vascular bundles and the efficiency in the cellulose hydrolysis in each sample. Lignin and hemicellulose contents of the samples increased from the pith to the rind region. Evaluation of the entire data set on the efficiency of the enzymatic hydrolysis and the chemical and morphological characteristics of the samples indicated that an appropriated parameter for predicting the cellulose conversion levels should account for the positive effect of high cellulose and low lignin plus hemicellulose contents and the detrimental effect assigned to the high abundance of vascular bundles. The available cellulose in the samples was calculated as the total cellulose divided by the sum of the contents of embedding compounds (lignin plus hemicellulose). The available cellulose value was divided by the area occupied by the vascular bundles in each sample, yielding a new parameter that fitted well to the cellulose conversion levels through a second order polynomial (r2 0.96). Maximal cellulose conversion of 85% was pointed out when the calculated parameter approximates to 0.6. This number was found when the available cellulose was around 1.8 and the area occupied by vascular bundles was 4%, which approximates the characteristics of the pith regions of the low-lignin-content hybrids