Structural and compositional changes in sugarcane bagasse subjected to hydrothermal and organosolv pretreatments and their impacts on enzymatic hydrolysis

Economical sustainability of cellulosic ethanol technology still requires considerable improvements in efficacies of both pretreatment and enzymatic hydrolysis steps. In this work a number of physical techniques were applied to characterize sugarcane bagasse samples that underwent hydrothermal and/or organosolv pretreatments under variable conditions and to correlated the observed changes with the efficiency of enzymatic hydrolysis. Confocal and field emission scanning electron microscopy studies revealed morphological changes in lignin distribution in the plant cell wall. The hydrothermal pretreatment caused a disorder in the arrangement of the lignin, whereas organosolv pretreatment partially removed lignin from bagasse and fraction of it redeposited at the surfaces of cellulose fibers. The delignification process was also analyzed by both chemical composition analysis and nuclear magnetic resonance. Pretreatment conditions leading to a significant increase of the efficiency of enzymatic hydrolysis were identified. Our studies open avenues for further biophysical investigations of pretreated lignocellulosic biomass, which could lead to its improved enzymatic hydrolysis.