Pseudo-Lignin Content Decreased with Hemicellulose and Lignin Removal, Improving Cellulose Accessibility, and Enzymatic
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Pseudo-Lignin Content Decreased with Hemicellulose and Lignin Removal, Improving Cellulose Accessibility, and Enzymatic Digestibility Alison Andrei Schmatz 1
& Ana Maria Salazar-Bryam
1
& Jonas Contiero
1
& Celso Sant’Anna
2
& Michel Brienzo
1
Received: 10 June 2020 / Accepted: 24 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The sugarcane bagasse is a heterogeneous material and needs a pretreatment to breakdown its complex structure to make cellulose accessible to enzyme action. This study aimed to evaluate pseudo-lignin formation, enzymatic hydrolysis of sugarcane fractions (leaf, external fraction, internode, and node), and bagasse after partial delignification and acid pretreatment. The leaf and external fraction presented the highest content of lignin, and external fraction was the most recalcitrant material resulting in lower glucose release. Pretreatment with diluted sulfuric acid (20% m/m or 2% m/v) generated 5 g/L of acetic acid and 2.07 g/L of 5hydroxymethylfurfural (external fraction in natura and leaf extractive-free, respectively). Furfural ranged between 0.11 g/L (node delignified) and 0.06 g/L (leaf, external fraction, and node in natura). A decrease was observed in pseudo-lignin formed with extractive-free and delignified biomasses, with different structure compared with non-delignified samples. The biomass partial delignification and subsequent pretreatment with dilute acid generate a material with fragmented anatomical structure, with improved cellulose accessibility, favoring enzymatic hydrolysis achieving more than 90% of glucose yield (up to 12 g/L). This study has shown strategies to decrease material heterogeneity and avoid pseudo-lignin formation as it results in lower recalcitrance and better efficiency of the enzymatic hydrolysis. Keywords Extractives . Diluted acid pretreatment . Cellulose . Glucose . Sugarcane fraction
Introduction The high demand for energy has led to the consumption of large quantities of fossil fuels, which have raised environmental concerns along with energy security issues. Global climate change caused by greenhouse gas emissions stimulated researchers to develop alternative fuels based on sustainable resources. Agro-energy crops and plant residues are the most promising, sustainable, low-cost feedstock for biofuel production and energy co-generation. Given the concern for sustainability and the need to maximize the use of natural resources, the use of sugarcane bagasse is receiving significant attention in biorefining applications as it is a promising resource for * Michel Brienzo [email protected] 1
Institute for Research in Bioenergy (IPBEN), São Paulo State University (UNESP), Rio Claro, SP, Brazil
2
Laboratory of Microscopy Applied to Life Science(Lamav), National Institute of Metrology, Quality and Technology (Inmetro), Duque de Caxias, RJ 25250-020, Brazil
conversion into biofuels such as second-generation ethanol and co-generation [1]. However, the sugarcane biomass is heterogeneous with differ
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