Elucidating the role of ferrous ion cocatalyst in enhancing dilute acid pretreatment of lignocellulosic biomass

Wang Wei, Wei Hui, Donohoe, Vinzant, Ciesielski, Gedvilas, Zeng Yining, Johnson, Ding Shi-You, Himmel, Tucker

Description

Recently developed iron cocatalyst enhancement of dilute acid pretreatment of biomass is a promising approach for enhancing sugar release from recalcitrant lignocellulosic biomass. However, very little is known about the underlying mechanisms of this enhancement. In the current study, our aim was to identify several essential factors that contribute to ferrous ion-enhanced efficiency during dilute acid pretreatment of biomass and to initiate the investigation of the mechanisms that result in this enhancement. Results During dilute acid and ferrous ion cocatalyst pretreatments, we observed concomitant increases in solubilized sugars in the hydrolysate and reducing sugars in the (insoluble) biomass residues. We also observed enhancements in sugar release during subsequent enzymatic saccharification of iron cocatalyst-pretreated biomass. Fourier transform Raman spectroscopy showed that major peaks representing the C-O-C and C-H bonds in cellulose are significantly attenuated by iron cocatalyst pretreatment. Imaging using Prussian blue staining indicated that Fe 2+ ions associate with both cellulose/xylan and lignin in untreated as well as dilute acid/Fe 2+ ion-pretreated corn stover samples. Analyses by scanning electron microscopy and transmission electron microscopy revealed structural details of biomass after dilute acid/Fe 2+ ion pretreatment, in which delamination and fibrillation of the cell wall were observed. Conclusions By using this multimodal approach, we have revealed that (1) acid-ferrous ion-assisted pretreatment increases solubilization and enzymatic digestion of both cellulose and xylan to monomers and (2) this pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the C-O-C and C-H bonds in cellulose.

Sujets

• Biomass
• Cellulose
• Corn stover
• Filter paper
• Fourier transform
• Raman spectroscopy

Informations

• Publié par: biomed
• Publié le: 01 janvier 2011
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Weiet al.Biotechnology for Biofuels2011,4:48 http://www.biotechnologyforbiofuels.com/content/4/1/48

R E S E A R C HOpen Access Elucidating the role of ferrous ion cocatalyst in enhancing dilute acid pretreatment of lignocellulosic biomass 1 11 11 21 Hui Wei , Bryon S Donohoe , Todd B Vinzant , Peter N Ciesielski , Wei Wang , Lynn M Gedvilas , Yining Zeng , 1 11* 2* David K Johnson , ShiYou Ding , Michael E Himmeland Melvin P Tucker

Abstract Background:Recently developed iron cocatalyst enhancement of dilute acid pretreatment of biomass is a promising approach for enhancing sugar release from recalcitrant lignocellulosic biomass. However, very little is known about the underlying mechanisms of this enhancement. In the current study, our aim was to identify several essential factors that contribute to ferrous ionenhanced efficiency during dilute acid pretreatment of biomass and to initiate the investigation of the mechanisms that result in this enhancement. Results:During dilute acid and ferrous ion cocatalyst pretreatments, we observed concomitant increases in solubilized sugars in the hydrolysate and reducing sugars in the (insoluble) biomass residues. We also observed enhancements in sugar release during subsequent enzymatic saccharification of iron cocatalystpretreated biomass. Fourier transform Raman spectroscopy showed that major peaks representing the COC and CH bonds in cellulose are significantly attenuated by iron cocatalyst pretreatment. Imaging using Prussian blue staining 2+ 2+ indicated that Fe ions associate with both cellulose/xylan and lignin in untreated as well as dilute acid/Feion pretreated corn stover samples. Analyses by scanning electron microscopy and transmission electron microscopy 2+ revealed structural details of biomass after dilute acid/Feion pretreatment, in which delamination and fibrillation of the cell wall were observed. Conclusions:By using this multimodal approach, we have revealed that (1) acidferrous ionassisted pretreatment increases solubilization and enzymatic digestion of both cellulose and xylan to monomers and (2) this pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the COC and CH bonds in cellulose. Keywords:dilute acid pretreatment, iron cocatalyst, ferrous ions, metal cocatalyst, biomass, cellulose, corn stover, cotton linter, filter paper, Fourier transform, Raman spectroscopy

Background Enzymatic biomass conversion enabled by dilute acid pre treatment processes has been studied for many years but remains one of the key obstacles to the economical pro duction of lignocellulosic biofuels today. Ferrous ion 2+ (hereinafter referred as Fe) enhancement of dilute acid pretreatment of biomass is a promising technology that

* Correspondence: [e-mail]; [e-mail] 1 Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA 2 National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA Full list of author information is available at the end of the article

enhances the release or conversion of sugars during pre 2+ treatment [1]. The economic benefit of adding Fe ions can be realized by reducing the severity of pretreatment conditions (a composite factor based on acid concentra tion, temperature and time) while retaining comparable conversion to biomass sugars. Fourier transform infrared spectroscopy (FTIR) was used to study the interaction between firstrow transition metal ions (to which Fe belongs) and glucose in the glassy state. The results showed that all bands of sugar skeletal vibration modes and all COH and CO vibration modes of glucose were shifted in metal ion/Dglucose complexes

© 2011 Wei et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.