Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility

Abstract

BackgroundIn recent years, biorefining of lignocellulosic biomass to produce multi-products such as ethanol and other biomaterials has become a dynamic research area. Pretreatment technologies that fractionate sugarcane bagasse are essential for the successful use of this feedstock in ethanol production. In this paper, we investigate modifications in the morphology and chemical composition of sugarcane bagasse submitted to a two-step treatment, using diluted acid followed by a delignification process with increasing sodium hydroxide concentrations. Detailed chemical and morphological characterization of the samples after each pretreatment condition, studied by high performance liquid chromatography, solid-state nuclear magnetic resonance, diffuse reflectance Fourier transformed infrared spectroscopy and scanning electron microscopy, is reported, together with sample crystallinity and enzymatic digestibility.ResultsChemical composition analysis performed on samples obtained after different pretreatment conditions showed that up to 96% and 85% of hemicellulose and lignin fractions, respectively, were removed by this two-step method when sodium hydroxide concentrations of 1% (m/v) or higher were used. The efficient lignin removal resulted in an enhanced hydrolysis yield reaching values around 100%. Considering the cellulose loss due to the pretreatment (maximum of 30%, depending on the process), the total cellulose conversion increases significantly from 22.0% (value for the untreated bagasse) to 72.4%. The delignification process, with consequent increase in the cellulose to lignin ratio, is also clearly observed by nuclear magnetic resonance and diffuse reflectance Fourier transformed infrared spectroscopy experiments. We also demonstrated that the morphological changes contributing to this remarkable improvement occur as a consequence of lignin removal from the sample. Bagasse unstructuring is favored by the loss of cohesion between neighboring cell walls, as well as by changes in the inner cell wall structure, such as damaging, hole formation and loss of mechanical resistance, facilitating liquid and enzyme access to crystalline cellulose.ConclusionsThe results presented herewith show the efficiency of the proposed method for improving the enzymatic digestibility of sugarcane bagasse and provide understanding of the pretreatment action mechanism. Combining the different techniques applied in this work warranted thorough information about the undergoing morphological and chemical changes and was an efficient approach to understand the morphological effects resulting from sample delignification and its influence on the enhanced hydrolysis results.

Side by Side Comparison of Chemical Compounds Generated by Aqueous Pretreatments of Maize Stover, Miscanthus and Sugarcane Bagasse

“…The composition of the three biomass feedstocks showed clear differences between the three species studied, and the individual composition is consistent with the range of values previously published for these feedstocks (Table 1) [21][22][23][24]. The total cell wall content in maize stover is lower than in the other biomasses, showing a higher proportion of soluble materials in the original biomass.…”

“…However, it cannot be excluded that the dimers in 20°C samples originate Fig. 5 Compounds structurally characterised in alkaline and acid pretreatment liquors (22)(23)(24)(25)(26)(27)(28)(29). See Supplemental Fig.…”

Removal of Pb (II) From Contaminated Water by Bagasse Adsorbent Modified with Dithizone

“…To date, removal of heavy metals, especially lead ions by means of bagasse, as a potentially effective adsorbent, has been developed (19)(20)(21). Various functional groups such as amino, hydroxyl, carboxyl, sulfate, and phosphate can be found in the chemical structure of bagasse, which may aid to adsorb heavy metals onto its surface (22).…”

Evaluation and Selection of Potential Biomass Sources of North-East India towards Sustainable Bioethanol Production

“…In previous studies, maximum hydrolytic efficiency of cellulose conversion (72%) was achieved from consecutive acid-base pretreatment of sugarcane BG (Rezende et al, 2011), employing a combination of 25 FPU of Accelerase 150 (DuPont, Wilmington, DE, USA) and 50 IU of β-glucanase from Novozyme 188 (Sigma Aldrich, USA). Similarly, cellulose conversion range between 27.5 and 47.7% and 15.9 and 48.8% was obtained by employing two enzyme preparations cellulase I and cellulase II, respectively, during 24 h hydrolysis (Santos et al, 2011).…”