Multifaceted characterization of sugarcane bagasse under different steam explosion severity conditions leading to distinct enzymatic hydrolysis yields

Pretreatment is an important technological step for the lignocellulose conversion into fuels and biochemicals. Steam explosion (STEX) pretreatment is a fast method for affecting of plant cell wall architecture by a sharp pressure change at high temperatures. Here, eight different STEX conditions were applied to sugarcane bagasse (SCB) samples using auto-catalyzed and sulfuric acid catalyzed processes under a range of combined severity factors (CSFs; from 0.37 to 1.34). Our results showed that STEX of auto-catalyzed and sulfuric acid-catalyzed SCB led to the removal of 70-80 % and 82-92 % of xylose, respectively. Enzymatic hydrolysis of auto-catalyzed and sulfuric acid catalyzed bagasse was performed of washed and un-washed pretreated material to access the impact of soluble inhibitors on overall cellulosic sugars recovery. Auto-catalyzed bagasse after washing showed significantly higher glucan conversion (96%) than washed bagasse after pretreatment (62%). On the other hand, sulfuric acid-catalyzed bagasse after washing had 94% glucan conversion as opposed to unwashed material which again had significantly smaller conversion levels (73%). Physical properties and chemical composition were characterized using high performance liquid chromatography, X-ray diffraction, C-13 solid-state nuclear magnetic resonance and confocal laser scanning microscopy. The obtained results contribute to understanding of an influence of the morphological changes resulting from pretreatments on the efficiency of enzymatic hydrolysis. We show that the changes in physical structure and chemical composition of the pretreated biomass might not be determined solely by combined severity factor of the pretreatments, but by the whole complexity of chemical modifications that different conditions of pretreatments introduce in the plant biomass samples.