Lignocellulosic biomass valorization: a study of plant biomass structure, composition, and enzymatic digestibility after being submitted to different pretreatment steps

• Autor(a) principal: Kane, Aissata Ousmane
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/76/76133/tde-14022023-103652/
• topic: Biomassa lignocelulósica; Cellulose nanofibers (CNF); Hidrólise enzimática; Lignocellulosic biomass; Nanofibras de celulose; Pré-tratamento; Pretreatment. Enzymatic hydrolysis

Bioenergy has been proposed as one way to significantly meet global energy demand and prevent environmental problems using renewable energy resources. The valorization of lignocellulosic biomass as a renewable feedstock for producing bioethanol and biomaterial has attracted much attention. However, efficient lignocellulosic biomass conversions require the development of strategies and technologies safe and inexpensive. Sugarcane is an agricultural crop produced in several tropical countries, notably Brazil. This work has investigated sugarcane wastes as potential raw materials to produce second-generation biofuels and nanomaterials. Different configurations of two-stage pretreatments were applied to sugarcane wastes (SCC, SCB, SCL) to produce fermentable sugars after enzymatic hydrolysis as well as nanocellulose via enzymatic hydrolysis and mechanical disintegration of cellulose-enriched material. Enzymatic hydrolysis yields of raw and pretreated sugarcane wastes were determined and correlated with structural, morphological, and composition changes after pretreatments. Overall, after combined pretreatments, enzymatic convertibility was highly efficient for all studies, reaching over 97% for SCC after acid-alkaline pretreatment (NaOH2% / H2SO42%), 91.2% for SCL acid-alkaline (H2SO41% / NaOH1%), 99.57 % for sugarcane bagasse after liquid hot water - alkaline sulfonation (H2O / Na2SO3 +NaOH). This efficiency was correlated to the removal of amorphous parts of lignocellulosic biomass, lignin, and/or hemicellulose, which also justify high crystallinity indices and crystallite sizes of pretreated biomass. An efficient carbohydrate extraction from sugarcane bagasse occurred during alkaline pretreatment using NaOH + H2O2, with a maximum delignification. Thermally and colloidally stable cellulose nanofibers were obtained. The enzymatic hydrolysis stage facilitated the defibrillation of blanched SCB, and the sulfonation introduced sulfonic groups in the CNF. The introduction of surface charges to CNF promotes their functionalization and widens their fields of application.