Bioconversion Of Cellulose Research Articles

Effect of the type and concentration of cellulose and temperature on metabolite formation by a fermentative thermophilic consortium

In this study, we hypothesized that anaerobic biodegradation of cellulose is influenced by cellulose type and concentration, temperature, and their interactions. Cellulose biodegradation by an anaerobic consortium was tested in thermophilic batch experiments that combined cellulase action, hydrolysis, and fermentation. Initially, the main constituents in the inocula were Thermoanaerobacter, Clostridium, and Acetivibrio spp. Four types of cellulose and a range of concentrations were used as feedstock with pathways involving hydrolysis and glycolysis to produce H2, CO2, acetate, and ethanol. Long fibrous cellulose, two types of microcrystalline cellulose, and filter paper squares were tested at several concentrations between 2 and 20 g/l as substrates. The yields ranged between 0.1 and 2.9 mmol H2 and 0.7–2.6 mmol ethanol per g cellulose. The rates ranged between 0.01 and 0.2 mmol H2, 0.03–0.2 mmol CO2, and 0.01–0.05 mmol ethanol per g cellulose·h. Statistical analyses indicated that the rates and yields of metabolite production were influenced by two-way interactions between the temperature, type, and concentration of cellulose. The results suggest that two-way interactions between experimental variables may impact the outcomes in cellulose bioconversion studies.

A cellulolytic fungal biofilm enhances the consolidated bioconversion of cellulose to short chain fatty acids by the rumen microbiome

The ability of the multispecies biofilm membrane reactors (MBM reactors) to provide distinguished niches for aerobic and anaerobic microbes at the same time was used for the investigation of the consolidated bioprocessing of cellulose to short chain fatty acids (SCFAs). A consortium based consolidated bioprocess (CBP) was designed. The rumen microbiome was used as the converting microbial consortium, co-cultivated with selected individual aerobic fungi which formed a biofilm on the tubular membrane flushed with oxygen. The beneficial effect of the fungal biofilm on the process yields and productivities was attributed to the enhanced cellulolytic activities compared with those achieved by the rumen microbiome alone. At 30 °C, the MBM system with Trichoderma reesei biofilm reached a concentration 39% higher (7.3 g/L SCFAs), than the rumen microbiome alone (5.1 g/L) using 15 g/L crystalline cellulose as the substrate. Fermentation temperature was crucial especially for the composition of the short chain fatty acids produced. The temperature increase resulted in shorter fatty acids produced. While a mixture of acetic, propionic, butyric, and caproic acids was produced at 30 °C with Trichoderma reesei biofilm, butyric and caproic acids were not detected during the fermentations at 37.5 °C carried out with Coprinopsis cinerea as the biofilm forming fungus. Apart from the presence of the fungal biofilm, no parameter studied had a significant impact on the total yield of organic acids produced, which reached 0.47 g of total SCFAs per g of cellulose (at 30 °C and at pH 6, with rumen inoculum to total volume ratio equal to 0.372).

Effect of Particle Size on the Kinetics of Enzymatic Hydrolysis of Microcrystalline Cotton Cellulose: a Modeling and Simulation Study.

As the bioconversion of cellulosic substrate to fuels is essential to suppress the dependence on conventional fossil fuels, development of new improved bioprocess engineering techniques are requisite for fulfilling the rising demand of biofuels throughout the world. For this purpose, the effect of particle size on enzymatic hydrolysis of cotton cellulose has been explored in great detail. The model simulations for the enzymatic hydrolysis of microcrystalline cotton cellulose of different concentrations (0.25-20mg/ml) were performed for the average particle size ranging from 0.78 to 25.52μm. A highest glucose yield (99.8%) was observed for the smallest particle size of 0.78μm in 50h of enzymatic hydrolysis. Effect of inhibition (competitive and non-competitive) on glucose yield was analyzed through the incorporation of product inhibition in the kinetic model. The extent of cleaving of 1-4 glycosidic bonds by cellulase was quantified by degree of polymerization (DP) of cotton polymers which also indicates that faster scission of bonds can be observed under competitive inhibition and, hence, more glucose yield. The model simulations shows that particle size reduction may be useful for reducing the long residence time required for the hydrolysis step in the bioconversion of cellulose to ethanol.

The effects of time and temperature in hydrothermal pretreatment on the enzymatic efficiency of wheat straw

An attempt to correlate biomass characteristics to its susceptibility to enzymes is often inconclusive via investigation of the variables of hydrothermal pretreatment. Based on an integrated analysis of physicochemical properties, cellulose bioconversion, loss of pentose sugars, formation of inhibitory products, and the cost of energy, the optimal hydrothermal operation for wheat straw (1:20 w/v%) was found. This optimal operation involved cooling the hydrolysates as soon as the temperature reached 180 °C. Finally, a total of 40.7% glucose and 70.3% sugars were recovered during subsequent enzymatic hydrolysis. Although treatment at a noticeably increased severity with a long incubation time could lead to almost 100% conversion of cellulose, the weight losses (mainly sugars) and inhibitors in the process liquid were not well suited for an industrial scale operation.

Localization of gene expression, tissue specificity of Populus xylosyltransferase genes by isolation and functional characterization of their promoters

Efficient bioconversion of cellulose into glucose using lignocellulose as the feedstock requires improved cell wall traits. Xylan is part of the matrix covering cellulose and linkages of xylan and lignin inhibit cellulases access. Xylose, an uncommon sugar in the yeast fermentation process, represents 20% of the lignocellulose mass fraction, thus xylan related genes are important targets for biotechnology. Initially, the isolation of candidate genes and their functional characterization is a prerequisite. A common strategy is to perform exhaustive promoter characterizations for candidate genes. Here, we report on the characterization of two xylosyltransferases-related gene promoters that were isolated upstream of the respective candidate genes in poplar, a promising feedstock for bioenergy that is characterized by its short-rotation. The species is known to have undergone recent whole genome duplication, thus finding duplicated gene sequences for xylosyltransferases based on phylogeny reconstruction but with distinct expression patterns is expected. To investigate these two genes closely related to the single, well-characterised Arabidopsis thaliana (At) irx10 gene, we constructed two binary vectors, each studying the full-length promoter of the respective gene. For the poplar (Ptr) gene, most likely the functionally closest to the At irx10 gene, localization of gene expression was studied using the green fluorescence protein (GFP). Poplar’s glucuronoxylan glucuronosyltransferase protein, PtrGUT2B, expression was localized in the inflorescence, and specifically in the xylem and along the fibres, suggesting that PtrGUT2B gene expression is associated with fibre production similar to the At irx10 gene. Conversely, the second, duplicated, poplar gene termed PtrGUT2A showed expression in the cambium/phloem, vascular bundles, in the primary xylem and the central cylinder that actively undergo cell divisions and differentiation as evidenced by driving s-glucuronidase (GUS) expression in these specific tissues. There was no staining detected in the mature secondary xylem or interfascicular fibres. Our study demonstrated that the PtrGUT2B is the true ortholog of irx10 and the two isolated promoters can be used to target tissue specific expression in plant biotechnology assays.

Developing cellulolytic Yarrowia lipolytica as a platform for the production of valuable products in consolidated bioprocessing of cellulose

BackgroundBoth industrial biotechnology and the use of cellulosic biomass as feedstock for the manufacture of various commercial goods are prominent features of the bioeconomy. In previous work, with the aim of developing a consolidated bioprocess for cellulose bioconversion, we conferred cellulolytic activity of Yarrowia lipolytica, one of the most widely studied “nonconventional” oleaginous yeast species. However, further engineering this strain often leads to the loss of previously introduced heterologous genes due to the presence of multiple LoxP sites when using Cre-recombinase to remove previously employed selection markers.ResultsIn the present study, we first optimized the strategy of expression of multiple cellulases and rescued selection makers to obtain an auxotrophic cellulolytic Y. lipolytica strain. Then we pursued the quest, exemplifying how this cellulolytic Y. lipolytica strain can be used as a CBP platform for the production of target products. Our results reveal that overexpression of SCD1 gene, encoding stearoyl-CoA desaturase, and DGA1, encoding acyl-CoA:diacylglycerol acyltransferase, confers the obese phenotype to the cellulolytic Y. lipolytica. When grown in batch conditions and minimal medium, the resulting strain consumed 12 g/L cellulose and accumulated 14% (dry cell weight) lipids. Further enhancement of lipid production was achieved either by the addition of glucose or by enhancing cellulose consumption using a commercial cellulase cocktail. Regarding the latter option, although the addition of external cellulases is contrary to the concept of CBP, the amount of commercial cocktail used remained 50% lower than that used in a conventional process (i.e., without internalized production of cellulases). The introduction of the LIP2 gene into cellulolytic Y. lipolytica led to the production of a strain capable of producing lipase 2 while growing on cellulose. Remarkably, when the strain was grown on glucose, the expression of six cellulases did not alter the level of lipase production. When grown in batch conditions on cellulose, the engineered strain consumed 16 g/L cellulose and produced 9.0 U/mL lipase over a 96-h period. The lipase yield was 562 U lipase/g cellulose, which represents 60% of that obtained on glucose. Finally, expression of the hydroxylase from Claviceps purpurea (CpFAH12) in cellulolytic Y. lipolytica procured a strain that can produce ricinoleic acid (RA). Using this strain in batch cultures revealed that the consumption of 11 g/L cellulose sustained the production of 2.2 g/L RA in the decane phase, 69% of what was obtained on glucose.ConclusionsIn summary, this study has further demonstrated the potential of cellulolytic Y. lipolytica as a microbial platform for the bioconversion of cellulose into target products. Its ability to be used in consolidated process designs has been exemplified and clues revealing how cellulose consumption can be further enhanced using commercial cellulolytic cocktails are provided.

Preparation and Evaluation of Coal Fly Ash/Chitosan Composites as Magnetic Supports for Highly Efficient Cellulase Immobilization and Cellulose Bioconversion.

Two magnetic supports with different morphologies and particle sizes were designed and prepared for cellulase immobilization based on chitosan and industrial by-product magnetic coal fly ash (MCFA). One was prepared by coating chitosan onto spherical MCFA particles to form non-porous MCFA@chitosan gel microcomposites (Support I) with a size of several micrometers, and the other was prepared using the suspension method to form porous MCFA/chitosan gel beads (Support II) with a size of several hundred micrometers. Cellulase was covalent binding to the support by glutaraldehyde activation method. The morphology, structure and magnetic property of immobilized cellulase were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and a vibrating-sample magnetometer. The cellulase loading on Support I was 85.8 mg/g with a relatlvely high activity recovery of 76.6%, but the immobilized cellulase exhibited low thermal stability. The cellulase loading on Support II was 76.8 mg/g with a relative low activity recovery of 51.9%, but the immobilized cellulase showed high thermal stability. Cellulase immobilized on Support I had a glucose productivity of 219.8 mg glucose/g CMC and remained 69.9% of the original after 10 cycles; whereas the glucose productivity was 246.4 mg glucose/g CMC and kept 75.5% of its initial value after 10 repeated uses for Support II immobilized cellulase. The results indicate that the two supports can be used as cheap and effective supports to immobilize enzymes.

Studying Nonproductive Adsorption Ability and Binding Approach of Cellobiohydrolase to Lignin during Bioconversion of Lignocellulose

Using fermentable sugars from lignocelluloses to produce chemicals and fuels was a way to resolve the energy crisis and environmental problems, but nonproductive adsorption of cellulase onto lignin is big challenge for bioconversion of cellulose to fermentable sugars. As cellobiohydrolase (CBH) is the main enzyme in cellulase mixture, understanding the adsorption mechanism of CBH onto lignin is important to enhance CBH catalytic efficiency by avoiding the nonproductive adsorption. This study suggested that CBH displayed high adsorption affinity to lignin, especially for the lignin isolated from liquid-hot-water pretreated substrate, and a stable combination of lignin-CBH was formed. The CBH adsorbed to lignin still had the catalytic ability on Avicel, although the ability was decreased. The possible reason, by molecular docking, was that the catalytic domain of CBH was irreversibly adsorbed onto lignin mainly through a hydrophobic cleft located oppositely to catalytic tunnel, not influencing the catalytic...

Production of the versatile cellulase for cellulose bioconversion and cellulase inducer synthesis by genetic improvement of Trichoderma reesei

BackgroundThe enzymes for efficient hydrolysis of lignocellulosic biomass are a major factor in the development of an economically feasible cellulose bioconversion process. Up to now, low hydrolysis efficiency and high production cost of cellulases remain the significant hurdles in this process. The aim of the present study was to develop a versatile cellulase system with the enhanced hydrolytic efficiency and the ability to synthesize powerful inducers by genetically engineering Trichoderma reesei.ResultsIn our study, we employed a systematic genetic strategy to construct the carbon catabolite-derepressed strain T. reesei SCB18 to produce the cellulase complex that exhibited a strong cellulolytic capacity for biomass saccharification and an extraordinary high β-glucosidase (BGL) activity for cellulase-inducing disaccharides synthesis. We first identified the hypercellulolytic and uracil auxotrophic strain T. reesei SP4 as carbon catabolite repressed, and then deleted the carbon catabolite repressor gene cre1 in the genome. We found that the deletion of cre1 with the selectable marker pyrG led to a 72.6% increase in total cellulase activity, but a slight reduction in saccharification efficiency. To facilitate the following genetic modification, the marker pyrG was successfully removed by homologous recombination based on resistance to 5-FOA. Furthermore, the Aspergillus niger BGLA-encoding gene bglA was overexpressed, and the generated strain T. reesei SCB18 exhibited a 29.8% increase in total cellulase activity and a 51.3-fold enhancement in BGL activity (up to 103.9 IU/mL). We observed that the cellulase system of SCB18 showed significantly higher saccharification efficiency toward differently pretreated corncob residues than the control strains SDC11 and SP4. Moreover, the crude enzyme preparation from SCB18 with high BGL activity possessed strong transglycosylation ability to synthesize β-disaccharides from glucose. The transglycosylation product was finally utilized as the inducer for cellulase production, which provided a 63.0% increase in total cellulase activity compared to the frequently used soluble inducer, lactose.ConclusionsIn summary, we constructed a versatile cellulase system in T. reesei for efficient biomass saccharification and powerful cellulase inducer synthesis by combinational genetic manipulation of three distinct types of genes to achieve the customized cellulase production, thus providing a viable strategy for further strain improvement to reduce the cost of biomass-based biofuel production.

Bioconversion of cellulose and simultaneous production of thermoactive exo- and endoglucanases by Fusarium oxysporum

Saccharification of cellulose is a promising method for production of biofuels. However, low bioconversion efficiency of cellulose to soluble sugars is a major challenge. In this study, a cellulolytic strain of Fusarium oxysporum was cultivated on pure cellulosic substrates (avicel, α-cellulose, carboxymethylcellulose and methylcellulose) and conversion efficiency into glucose was investigated. Production of exo- and endoglucanases during the bioconversion process was evaluated. Influence of pH on saccharification of cellulose and enzyme production by F. oxysporum were determined. Highest yield of glucose (1.76 μmol/ml) was obtained from F. oxysporum on methyl cellulose at 192 h under basal conditions. Liberated glucose under optimized condition of pH 6.0 at 96 h of fermentation was 2.12 μmol/ml with maximum production of exo- and endoglucanases (23.70 and 34.72 U/mg protein, respectively). The crude exo- and endoglucanases had optimum activities at pH 8.0, 70 °C and pH 7.0, 50 °C, respectively. The enzymes were stable over pH of 4.0–7.0 with relative residual activity above 60% after 1 h incubation. Exoglucanase activity was enhanced by Ca2+ and Cu2+ at 5 mM and Mg2+ at 10 mM. Endoglucanase activity was greatly enhanced in the presence of Mn2+, Ca2+, Mg2+, Cu2+ and Fe3+ at 5 and 10 mM. Activities of both enzymes were inhibited in the presence of Hg2+ at 5 and 10 mM. Results show that F. oxysporum possessed good cellulolytic enzyme system for efficient conversion of cellulose. Exhibited thermotolerance of exoglucanase with the striking tolerance of endoglucanase to metal ions demonstrate potentials of enzymes for biofuel industry.

Methanogenic degradation of toilet-paper cellulose upon sewage treatment in an anaerobic membrane bioreactor at room temperature

Toilet-paper cellulose with rich but refractory carbon sources, are the main insoluble COD fractions in sewage. An anaerobic membrane bioreactor (AnMBR) was configured for sewage treatment at room temperature and its performance on methanogenic degradation of toilet paper was highlighted. The results showed, high organic removal (95%), high methane conversion (90%) and low sludge yield (0.08gVSS/gCOD) were achieved in the AnMBR. Toilet-paper cellulose was fully biodegraded without accumulation in the mixed liquor and membrane cake layer. Bioconversion efficiency of toilet paper approached 100% under a high organic loading rate (OLR) of 2.02gCOD/L/d and it could provide around 26% of total methane generation at most of OLRs. Long sludge retention time and co-digestion of insoluble/soluble COD fractions achieving mutualism of functional microorganisms, contributed to biodegradation of toilet-paper cellulose. Therefore the AnMBR successfully implemented simultaneously methanogenic bioconversion of toilet-paper cellulose and soluble COD in sewage at room temperature.

Toward a fundamental understanding of cellulase‐lignin interactions in the whole slurry enzymatic saccharification process

AbstractLignocellulosic biomass is a promising feedstock for sustainable production of non‐food building‐block sugars. This bioconversion process is preferentially carried out through the whole slurry enzymatic saccharification of the pre‐treated lignocellulosic substrates. However, dissolved lignin, residual lignin, and lignin‐derived phenolic molecules in the pre‐treated biomass slurry can all trigger the decrease in activity and stability of cellulases, as well as the unfavorable enzyme recyclability. The hydrolyzing efficiencies can be considerably hindered by the lignin‐induced non‐productive binding of cellulases through various mechanisms. Three major non‐covalent forces, i.e., hydrophobic, electrostatic, and hydrogen bonds interactions, can occur between the amino acid residues in cellulases and the functional groups in lignin. Various strategies such as enzyme engineering, substrate modification, additive blocking have been intensively developed to minimize the cellulase‐lignin interactions. To investigate the impacts and benefits of different mechanisms and processes, this paper provides a systematic overview of the current opinions about the non‐productive binding of cellulase to lignin. Through better understanding of their interactions it is our hope that the enzyme binding groups in lignin could be properly quenched by using new pre‐treatment methods and/or biochemical processing strategies to increase the efficiency of cellulose bioconversion. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Development of an E. coli strain for one-pot biofuel production from ionic liquid pretreated cellulose and switchgrass

Integrating an ionic liquid tolerantE. colistrain with an ionic liquid tolerant cellulase for bioconversion of pretreated hydrolysate and cellulose to a bio jet-fuel precursor.

Pretreating cellulases with hydrophobins for improving bioconversion of cellulose: an experimental and computational study

An experimental and computational study on a strategy for biomass degradation in biofuel production, pretreating cellulases with hydrophobins.

Bioconversion of Cellulose to Biofuels

Major focus of Biotechnology in the early 1980s was in understanding the Life Science. But to meet societal energy challenge, understanding the capabilities of Life Sciences is at different stage today. Increase in industrialisation and motorisation has led to steep rise of demand for petroleum-based fuels. The sources of these fossil fuels are becoming exhausted, and now it is time to think about an alternative source. In this context bioconversion of biomass into biofuels seems to be a promising, sustainable and an eco-friendly technology. Lot of research has been done to convert most abundant source of biomass, cellulose to produce biofuels. Strain improvement methods, recombinant DNA technologies and selection of strains by breeding method are some of the methods used for enhancing biofuels production at industrial-scale. This review mainly focuses on bioconversion of Lignocellulosic biomass into biofuels.

Optimizing the composition of cellulase enzyme complex from Penicillium verruculosum: Enhancing hydrolytic capabilities via genetic engineering

Modern technologies for the enzyme hydrolysis of cellulose-containing raw materials allow the production of sugars from which alcohols (biofuel), organic and amino acids, biopolymers, feed additives, and other value-added products can be obtained via microbiological conversion. Three types of cellulolytic enzymes are required for the bioconversion of cellulose containing materials: endoglucanase, cellobiohydrolase, and s-glucosidase. The prospects for improving the hydrolytic capabilities of the enzyme complex secreted from Penicillium verruculosum are investigated in this work by means of genetic engineering to add different combinations and ratios of homologous and heterologous cellulases: endoglucanase IV (EGIV) of Trichoderma reesei, endoglucanase II (EGII), and cellobiohydrolase I (CBHI) of P. verruculosum, along with s-glucosidase (s-GLU) of Aspergillus niger. The optimum ratio of components is determined and the catalytic activity of enzymatic complexes is increased by as much as 100%.

Microalgae as a Feedstock for Biofuel Precursors and Value-Added Products: Green Fuels and Golden Opportunities

The prospects of biofuel production from microalgal carbohydrates and lipids coupled with greenhouse gas mitigation due to photosynthetic assimilation of CO2 have ushered in a renewed interest in algal feedstock. Furthermore, microalgae (including cyanobacteria) have become established as commercial sources of value-added biochemicals such as polyunsaturated fatty acids and carotenoid pigments used as antioxidants in nutritional supplements and cosmetics. This article presents a comprehensive synopsis of the metabolic basis for accumulating lipids as well as applicable methods of lipid and cellulose bioconversion and final applications of these natural or refined products from microalgal biomass. For lipids, one-step in situ transesterification offers a new and more accurate approach to quantify oil content. As a complement to microalgal oil fractions, the utilization of cellulosic biomass from microalgae to produce bioethanol by fermentation, biogas by anaerobic digestion, and bio-oil by hydrothermal liquefaction are discussed. Collectively, a compendium of information spanning green renewable fuels and value-added nutritional compounds is provided.

Metagenome approaches revealed a biological prospect for improvement on mesophilic cellulose degradation.

Improvement on the bioconversion of cellulosic biomass depends much on the expanded knowledge on the underlying microbial structure and the relevant genetic information. In this study, metagenomic analysis was applied to characterize an enriched mesophilic cellulose-converting consortium, to explore its cellulose-hydrolyzing genes, and to discern genes involved in methanogenesis. Cellulose conversion efficiency of the mesophilic consortium enriched in this study was around 70%. Apart from methane, acetate was the major fermentation product in the liquid phase, while propionate and butyrate were also detected at relatively high concentrations. With the intention to uncover the biological factors that might shape the varying cellulose conversion efficiency at different temperatures, results of this mesophilic consortium were then compared with that of a previously reported thermophilic cellulose-converting consortium. It was found that the mesophilic consortium harbored a larger pool of putative carbohydrate-active genes, with 813 of them in 54 GH modules and 607 genes in 13 CBM modules. Methanobacteriaceae and Methanosaetaceae were the two methanogen families identified, with a preponderance of the hydrogenotrophic Methanobacteriaceae. In contrast to its relatively high diversity and high abundance of carbohydrate-active genes, the abundance of genes involved in the methane metabolism was comparatively lower in the mesophilic consortium. A biological enhancement on the methanogenic process might serve as an effective option for the improvement of the cellulose bioconversion at mesophilic temperature.

Lignocellulosic waste material as substrate for Avicelase production by a new strain of Paenibacillus chitinolyticus CKS1

A novel strain of Paenibacillus chitinolyticus CKS1 was isolated from forest soil and identified as a potent cellulase producer. The strain was able to grow on various commercial substrates including microcrystalline cellulose (Avicel), carboxymethylcellulose (CMC), and cellobiose but also on lignocellulosic waste material such as medicinal herbs waste and sawdust. On all these substrates the strain produced cellulase composed of two subunits (∼70 and ∼45 kDa) that was active on CMC, Avicel and filter paper. The maximal Avicelase activity (1.94 U/ml) was reached in a medium that contained 0.1% (w/v) of medicinal herbs waste, 3 g l−1 of yeast extract and 5.0 g l−1 of casein hydrolysate in 0.1 M phosphate buffer pH 7, after 48 h of incubation at 30 °C. The Avicelase performed optimally at 80 °C and at pH 4.8. Addition of K+ increased the Avicelase activity almost three fold and the enzyme retained 48.39% of the initial activity after 60 min. The product of Avicel and CMC hydrolysis was glucose with traces of other soluble sugars, indicating that the crude cellulase produced on waste material using the novel P. chitinolyticus strain CKS 1 could be used in eco-friendly processes of cellulose bioconversion, such as enzymatic saccharification of lignocellulosic materials in processes performed under acidophilic conditions and high temperatures.

Visualization of Miscanthus×giganteus cell wall deconstruction subjected to dilute acid pretreatment for enhanced enzymatic digestibility.

BackgroundThe natural recalcitrance of lignocellulosic plant cell walls resulting from complex arrangement and distribution of heterogeneous components impedes deconstruction of such cell walls. Dilute acid pretreatment (DAP) is an attractive method to overcome the recalcitrant barriers for rendering enzymatic conversion of polysaccharides. In this study, the internodes of Miscanthus × giganteus, a model bioenergy crop, were subjected to DAP to yield a range of samples with altered cell wall structure and chemistry. The consequent morphological and compositional changes and their possible impact on saccharification efficiency were comprehensively investigated. The use of a series of microscopic and microspectroscopic techniques including fluorescence microscopy (FM), transmission electron microscopy (TEM) and confocal Raman microscopy (CRM)) enabled correlative cell wall structural and chemical information to be obtained.ResultsDAP of M. × giganteus resulted in solubilization of arabinoxylan and cross-linking hydroxycinnamic acids in a temperature-dependent manner. The optimized pretreatment (1% H2SO4, 170°C for 30 min) resulted in significant enhancement in the saccharification efficiency (51.20%) of treated samples in 72 h, which amounted to 4.4-fold increase in sugar yield over untreated samples (11.80%). The remarkable improvement could be correlated to a sequence of changes occurring in plant cell walls due to their pretreatment-induced deconstruction, namely, loss in the matrix between neighboring cell walls, selective removal of hemicelluloses, redistribution of phenolic polymers and increased exposure of cellulose. The consequently occurred changes in inner cell wall structure including damaging, increase of porosity and loss of mechanical resistance were also found to enhance enzyme access to cellulose and further sugar yield.ConclusionsDAP is a highly effective process for improving bioconversion of cellulose to glucose by breaking down the rigidity and resistance of cell walls. The combination of the most relevant microscopic and microanalytical techniques employed in this work provided information crucial for evaluating the influence of anatomical and compositional changes on enhanced enzymatic digestibility.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0282-3) contains supplementary material, which is available to authorized users.