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

Author(s)

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

Affiliation

^[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

• Document type: Journal article
• Source: BIOTECHNOLOGY FOR BIOFUELS; v. 8, AUG 5 2015.
• Web of Science Citations: 37

Abstract

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)

• FAPESP's process: 10/11135-6 - Structural and morphological aspects of the cell-wall degradation and its biopolymers
• Grantee: Camila Alves de Rezende
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 08/56255-9 - Structure and function of enzymes and auxiliary proteins from Trichoderma, active in cell-wall hydrolysis
• Grantee: Igor Polikarpov
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants
• FAPESP's process: 10/08370-3 - Biophysical and biochemical studies of exoglucanases from Trichoderma harzianum involved in the biodegradation of cellulose
• Grantee: Wanius José Garcia da Silva
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/52362-5 - Targeted analysis of microbial lignocellulolytic secretomes: a new approach to enzyme discovery
• Grantee: Igor Polikarpov
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/18354-8 - Dynamics and structure of polymer systems as studied by nuclear magnetic resonance
• Grantee: Eduardo Ribeiro de Azevedo
• Support Opportunities: Regular Research Grants