Quantitative C-13 MultiCP solid-state NMR as a tool for evaluation of cellulose crystallinity index measured directly inside sugarcane biomass

Autor(es)

Bernardinelli, Oigres Daniel ^[1] ; Lima, Marisa Aparecida ^[1] ; Rezende, Camila Alves ^{[1, 2]} ; Polikarpov, Igor ^[1] ; deAzevedo, Eduardo Ribeiro ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13660970 Sao Carlos, SP - Brazil

^[2] Univ Campinas UNICAMP, Inst Quim, BR-13084971 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: BIOTECHNOLOGY FOR BIOFUELS; v. 8, AUG 5 2015.
• Citações Web of Science: 37

Resumo

Background: The crystallinity index (CI) is often associated with changes in cellulose structure after biological and physicochemical pretreatments. While some results obtained with lignocellulosic biomass demonstrate a progressive increase in the CI as a function of pretreatments, it is also shown that the CI can significantly vary depending on the choice of the measurement method. Besides, the influence of the CI on the recalcitrance of biomass has been controversial for a long time, but the most recent results tend to point out that the efficiency of pretreatments in reducing the recalcitrance is not clearly correlated with the decrease of the CI. Much of this controversy is somewhat associated with the inability to distinguish between the CI of the cellulose inside the biomass and the CI of the full biomass, which contains other amorphous components such as lignin and hemicellulose. Results: Cross polarization by multiple contact periods (Multi-CP) method was used to obtain quantitative C-13 solid-state nuclear magnetic resonance (ssNMR) spectra of sugarcane bagasse biomass submitted to two-step pretreatments and/or enzymatic hydrolysis. By comparing the dipolar filtered Multi-CP C-13 NMR spectra of untreated bagasse samples with those of samples submitted to acid pretreatment, we show that a 1% H2SO4-assisted pretreatment was very effective in removing practically all the hemicellulose signals. This led us to propose a spectral editing procedure based on the subtraction of MultiCP spectra of acid-treated biomass from that of the extracted lignin, to obtain a virtually pure cellulose spectrum. Based on this idea, we were able to evaluate the CI of the native cellulose inside the sugarcane bagasse biomass. Conclusions: The results show the validity of the proposed method as a tool for evaluating the variations in the CI of the cellulose inside biomasses of similar kinds. Despite a clear increase in the CI of biomass as measured by X-ray diffraction, no significant variations were observed in the CI of the cellulose inside the biomass after a particular 1% H2SO4/0.25-4% NaOH chemical-assisted pretreatments. The CI of cellulose inside the biomass solid fraction that remained after the enzymatic hydrolysis was also evaluated. The results show a slight increase in crystallinity. (AU)

• Processo FAPESP: 10/11135-6 - Aspectos estruturais e morfológicos da degradação da parede celular e seus biopolímeros
• Beneficiário: Camila Alves de Rezende
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 08/56255-9 - Structure and function of enzymes and auxiliary proteins from Trichoderma, active in cell-wall hydrolysis
• Beneficiário: Igor Polikarpov
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOEN - Temático
• Processo FAPESP: 10/08370-3 - Estudos biofísicos e bioquímicos de exoglicanases do fungo Trichoderma harzianum envolvidas na biodegradação da celulose
• Beneficiário: Wanius José Garcia da Silva
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 10/52362-5 - Targeted analysis of microbial lignocellulolytic secretomes: a new approach to enzyme discovery
• Beneficiário: Igor Polikarpov
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 09/18354-8 - Dinâmica e estrutura de sistemas poliméricos estudados por ressonância magnética nuclear
• Beneficiário: Eduardo Ribeiro de Azevedo
• Modalidade de apoio: Auxílio à Pesquisa - Regular