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Lignocellulose materials, essentially consisting of lignin, cellulose and hemicelluloses, are abundant sources of fermentable sugars. The bast fiber of Crotalaria juncea (Sunn hemp), a native cover crop of India, was used as feedstock for this study. The primary objective of this study was to add value to the waste C. juncea bast fiber. The same was achieved by pretreating the waste fiber using alkaline peroxide solution at various process conditions. The optimal process condition for alkaline peroxide pretreatment was identified for the fiber to pretreatment solution (S/S) ratio of 1/40 at 50°C for 5h with respect to all response variables (lignin removal, hemicellulose recovery, recovery of solid pretreated material, and crystallinity of lignocellulose). Three-way ANOVA results revealed that S/S ratio had no significant effect; whereas, both temperature and time, and the combination of parameters, exhibited significant effect on response variables. The characteristic peaks associated with lignin and cellulose demonstrated a higher amount of lignin removal and increased cellulose content with elevated treatment time. Autoclave assisted pretreatment proved to be inefficient due to removal of lower amount of lignin in addition to higher hemicellulose degradation. On the other hand, pretreatment using ultrasound was found to be most effective in removing lignin, liberating hemicelluloses along with diminition in cellulose crystallinity.

Fall leaves are biodegraded and composted naturally in forests but they are wastes for urban areas. Moreover, they are widely available cellulose sources but have limited applications. Alkaline peroxide treatment of bioresources is one of the most widely studied clean methods for both delignification and hemicellulose removal but there is no study about application of that method on fall leaves at room temperature. In this study, the effect of alkaline peroxide treatment of fall leaves at room temperature on hemicellulose recovery and cellulose delignification were investigated. Fall leaves (FL) were treated with 0.3-3.0 M NaOH + 0-3 M H2O2 at room temperature. Hemicellulose recovery and cellulose delignification values were analyzed. Hemicellulose recovery and cellulose delignification increased and yield decreased by increasing NaOH and H2O2 concentrations. Hemicellulose recovery and cellulose delignification reached to the maximum levels, 99.5% and 81.6% respectively, at 3M NaOH + 3M H2O2 treatment condition. The end products were confirmed by analytically, spectrally and morphologically. Wasted fall leaves were turned into useful hemicellulose and cellulose products by using clean alkaline peroxide treatment at room temperature. The products can be further processed by known methods into other industrial products.

To improve ethanol productivity with few inhibitors generated, a novel process of combined alkaline peroxide (AP) pretreatment and semi-simultaneous saccharification and fermentation (SSSF) was developed in this work. Pretreatment with 10% (g H2O2/g wood) H2O2 at 160°C for 2h followed by SSSF was found to be the optimal combination with remarkably increased ethanol yield. The proposed process resulted in 63.1% of ethanol yield, which was about five times more than that of the untreated sample that was processed using conventional simultaneous saccharification and fermentation (SSF). The efficient conversion was ascribed to the high delignification efficiency (64.9%) of AP pretreatment, which led to incompact structure and generation of fewer inhibitors during SSSF (c. 6g/L of lactic acid) than SSF (c. 10 g/L of lactic acid). This combined approach was proved to be an effective method for the promotion of the bioconversion of lignocellulosic materials.

The efficient delignification of low-cost lignocellulosic biomass is of utmost importance for its viable conversion to biofuel. In the current study, agricultural waste biomass of Sterculia foetida fruit shell was pretreated by heating at 60 ℃ and 121 ℃ in the presence of alkaline and alkaline peroxide conditions. The objective was to study the effects of concentration of NaOH & H2O2 and temperature on lignin removal efficiency and reducing sugar content. The structural and functional changes caused to the biomass were also studied using FTIR and XRD analysis. The optimum lignin removal of 81.66% was achieved by heating at 60 ℃ for 3 hours using 3% H2O2 and 5% NaOH aqueous solution showing an increase in crystallinity of the pretreated samples, removal of lignin as well as easy accessibility of cellulose and also indicates reduction of yield due to in situ degradation of the released sugars in the presence of NaOH and H2O2 at higher chemical concentrations. The developed pretreatment procedure showed appreciable delignification of the biomass which could be easily scaled up for continuous operations at low costs.

The complex and ordered arrangements of the lignocellulosic materials make them recalcitrant for their conversions to ethanol. Pretreatment is a crucial step in overcoming these hindrances. In this study, a 23-full factorial design of experiments optimization technique was applied on the alkaline peroxide oxidation pretreatments of rice husks biomass. The low–high levels of the influencing variables on pretreatments were; temperature (100–120 °C), time (1–2 h), % (v/v)H2O2 concentration (1–3%). Under the prevailing pretreatments, the optimum conditions were predicted and validated to be 109 °C, 2 h, and 1.38% H2O2 which yielded 56% (w/w) cellulose content, 55% (w/w) hemicellulose solubilization, and 48% (w/w) lignin removal. At the established optimum pretreatment conditions, and considering variations in biomass and enzymes loadings, maximum reducing sugars production was 205 mg/g dry biomass at different enzymatic hydrolysis conditions of 3% biomass loading, hydrolysis temperature of 45 °C, hydrolysis time of 24 h, and 35 FPU/g cellulose enzyme loading. The highest cellulose conversion of 33% yielded 24 g/L ethanol at the end of the first day of saccharification and fermentation. Physical, structural, and morphological investigations on raw and treated materials using tools such as stereomicroscopy, scanning electron microscopy, and fourier transform infrared spectroscopy further revealed the effectiveness of chosen method on rice husks biomass.

Biomass recalcitrance is considered to be one of the impediments in bioconversion of lignocellulosic biomass (LCB) to sugars. Rice straw, a potential lignocellulosic waste, owing to the surplus availability, renewability and high carbohydrate content was used as a model LCB in the present study. The alkaline hydrogen peroxide-assisted wet air oxidation (APWAO) was evaluated as plausible pretreatment for rice straw based on the 23—factorial experimental design with a goal to reduce biomass recalcitrance by enhancing the cellulose recovery, hemicellulose solubilization, lignin removal and concomitantly generating limited degradation products. APWAO resulted in an overall cellulose recovery ranging from 80.54 to 93.02%, hemicellulose solubilization of 36.44–82.08% and lignin removal of 65.95–81.11% (all on w/w basis) respectively and absence of potent inhibitors viz. furfural and 5-hydroxymethylfurfural. The statistically significant pretreatment factors that affected each of these responses were assessed and optimum pretreatment conditions were determined to be biomass soaking in 0.5% H2O2 for 14 h succeeded by wet air oxidation (WAO) at 190 °C, 6 bar, 20 min by multi-objective numerical optimization. Further, the morphological and structural changes occurring as a result of pretreatment were scrutinized using SEM and FT-IR. APWAO further ensued in enhanced cellulose accessibility during enzymatic saccharification indicated by the glucose yield ranging from 113.97 to 200.34 g/kg untreated rice straw. Thus, the combined pretreatment (APWAO) i.e. pre-soaking in alkaline H2O2 followed by WAO was shown to enhance glucose yields owing to significant delignification.

Selective biomass fractionation into carbohydrates and lignin is a key challenge in the conversion of lignocellulosic biomass to fuels and chemicals. In the present study, alkaline hydrogen peroxide (AHP) pretreatment was investigated to fractionate lignin from polysaccharides in corn stover (CS), with a particular emphasis on the fate of the lignin for subsequent valorization. The influence of peroxide loading on delignification during AHP pretreatment was examined over the range of 30–500 mg H2O2/g dry CS at 50 °C for 3 h. Mass balances were conducted on the solid and liquid fractions generated after pretreatment for each of the three primary components, lignin, hemicellulose, and cellulose. AHP pretreatment at 250 mg H2O2/g dry CS resulted in the pretreated solids with more than 80% delignification consequently enriching the carbohydrate fraction to >90%. Two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy of the AHP pretreated residue shows that, under high peroxide loadings (>250 mg H2O2...

Effects of alkaline peroxide (AP) pre-treatment were investigated with respect to the extracted cellulose fibres from the vascular bundles of oil palm (Elaeis guineensis) fronds (OPF) rachis at different AP concentrations. The extracted fibres were prepared through the mechanical fibrillation resulting from the AP pre-treatment concentrations of the rachis. The cellulose fibres obtained were characterized using microscopic (SEM), spectroscopic (FTIR), thermal (TGA-DTG), and X-ray diffraction (XRD) techniques. The screen pulp yield was between 38.07% and 42.69%, which increased with the increase in the AP concentrations. The SEM showed a significant separation of the fibres after the AP pretreatment. FTIR spectroscopy and TGA showed significant dissolution of both lignin and hemicellulose molecules from the treated biomass at higher alkaline peroxide concentrations. The thermal stability of the extracted fibres ranged from 366 oC to 392 oC while the XRD results showed that the cellulose fibre extracted at H2O2/NaOH ratio of 2.5%: 2.0%,w/v AP concentrations gave the highest percentage crystallinity (35.7%). The handsheet made from the cellulose fibre showed that tensile, burst, and tear indexes increased with an increase in AP concentration. Duncan Multiple Range Test shows that mild alkaline peroxide pretreatment (medium concentrations) is best favoured for paper making pulp and bio-composite production.

Developing economical and sustainable fractionation technology of lignocellulose cell walls is the key to reaping the full benefits of lignocellulosic biomass. This study evaluated the potential of metal chloride-assisted p-toluenesulfonic acid (p-TsOH) hydrolysis at low temperatures and under acid concentration for the co-production of sugars and lignocellulosic nanofibrils (LCNF). The results indicated that three metal chlorides obviously facilitated lignin solubilization, thereby enhancing the enzymatic hydrolysis efficiency and subsequent cellulose nanofibrillation. The CuCl2-assisted hydrotropic pretreatment was most suitable for delignification, resulting in a relatively higher enzymatic hydrolysis efficiency of 53.2%. It was observed that the higher residual lignin absorbed on the fiber surface, which exerted inhibitory effects on the enzymatic hydrolysis, while the lower lignin content substrates resulted in less entangled LCNF with thinner diameters. The metal chloride-assisted rapid and low-temperature fractionation process has a significant potential in achieving the energy-efficient and cost-effective valorization of lignocellulosic biomass.

The xylan-rich hemicellulose components of sugarcane bagasse were sequentially extracted with pressurized hot-water extraction (PHWE) and alkaline peroxide. The hemicelluloses were found to contain mainly arabinoxylans with varying substitutions confirmed by different chemical and spectroscopic methods. The arabinoxylans obtained from PHWE were found to be more branched compared to those obtained after alkaline extraction. Sequential extraction could be useful for the isolation of hemicelluloses with different degree of branching, molar mass, and functional groups from sugarcane bagasse, which can be of high potential use for various industrial applications.

Lespedeza crytobotrya is a shrub species with properties of substantial biomass and widely distributes in the desert region of China. The cellulose separated from Lespedeza after pre-treatment can be enzymatic hydrolyzed into glucose for ethanol or other chemicals production, which are important renewable fuels or raw material for other material synthesis. Moreover it also can be used for cellulosic material production. So it is necessary to evaluate the cellulose of Lespedeza crytobotrya before its utilization. In this study four cellulosic fractions were isolated by pretreatment with low severity steam and post-treatment with alkaline peroxide. They were comparatively studied by sugar analysis and the average degree of polymerization. After alkaline peroxide post-treatment, the hemicelluloses in the cellulosic fractions were removed markedly. The treatment intensity had a profound effect on the average degree of polymerization, which was increased firstly and then decreased. A combination of low severity steam pretreatment and alkaline peroxide post-treatment is an effective method for Lespedeza stalks to obtain high glucose yield.

Olive tree biomass (OTB) can be used for producing second generation bioethanol. In this work, extracted OTB was subjected to fractionation using a sequential acid/alkaline oxidative pretreatment. In the first acid stage, the effects of sulfuric acid concentration and reaction times at 130°C were investigated. Up to 71% solubilization of hemicellulosic sugars was achieved under optimized conditions (2.4% H2SO4, 84min). In the second stage, the influence of hydrogen peroxide concentration and process time were evaluated at 80°C. Approximately 80% delignification was achieved under the best operational conditions (7% H2O2, 90min) within the experimental range studied. This pretreatment produced a substrate with 72% cellulose that was highly accessible to enzymatic attack, yielding 82g glucose/100g glucose in delignified OTB. Ethanol production from both hemicellulosic sugars solubilized in the acid pretreatment and glucose from enzymatic hydrolysis of delignified OTB yielded 15g ethanol/100g OTB.

Alkaline hydrogen peroxide (AHP) pretreatment and enzymatic saccharification were evaluated for conversion of corn stover cellulose and hemicellulose to fermentable sugars. Corn stover used in this study contained 37.0±0.2% cellulose, 26.8±0.2% hemicellulose, and 18.0±0.1% lignin on dry basis. Under the optimum conditions of AHP pretreatment [2% H2O2 (v/v), pH 11.5, 35°C, 24 h] of corn stover (10%, w/v) and enzymatic saccharification (45°C, pH 5.0, 72 h) with 0.1% (w/v) Tween 20, a total of 558±12 mg of fermentable sugars was obtained per g stover, which is equivalent to 79.5% of theoretical sugar yield. Most of the lignin (82%) was removed from corn stover. The AHP pretreated and enzymatically saccharified corn stover hydrolyzate was fermented by recombinant Escherichia coli strain FBR 5 at pH 6.5 and 37°C for 96 h to produce 23.9±0.9 g ethanol from 56.6±1.6 g total sugars per L with an ethanol yield of 0.42 g/g available sugars and 0.24 g/g corn stover, which is equivalent to 67% of theoretical...

The steam pre-treatment with low severity preserves valuable biomass components, and further delignification with alkaline peroxide could improve hydrolysis. A combination of low severity steam pretreatment and alkaline peroxide post-treatment of Lespedeza stalks was investigated. The post-treatment of steam-pretreated Lespedeza stalks with alkaline peroxide significantly increased the cellulose content and changed the structure of the cellulose-rich fractions. A glucose yield of 503.5 mg g−1 raw material from enzyme hydrolysis was obtained when the steam-pretreated material (184 °C for 4 min) was post-treated with 2% hydrogen peroxide at 60 °C for 24 h with a substrate concentration of 3.3%. Its hydrolysis yield is 88.8%, which is higher than that of samples processed by steam pretreatment alone (63.7%). The samples obtained by post-treatment with alkaline peroxide were found to have a smoother surface and looser structure in scanning electron microscopy images. The isolated lignin preparations had a yield range from 10.9 to 14.7 (% dry matter). The lignin was characterized by thermogravimetric analysis/differential thermal analysis, Fourier transform infrared spectroscopy, and gel permeation chromatography. Alkaline peroxide treatment increased the thermal stability of lignin, and decreased the amounts of all functional groups. Depolymerization and repolymerization occurred during the alkaline peroxide treatment.

The cellulose content of substrate is one of the most important factors for ethanol production from lignocellulose. To increase the cellulose content of substrate and ethanol yield in Simultaneous saccharification and fermentation (SSF), a pretreatment method coupling steam explosion with alkaline peroxide for wheat straw was studied. After the complex pretreatment, the cellulose content in wheat straw increased from 31.5% to 67.2%. In the hydrolysate of wheat straw pretreated with the complex method and steam explosion, the glucose concentration was 110.9 g/L and 67.8 g/L, respectively. The optimal conditions for SSF were 40 degrees C, 120 h, cellulase loading 40 FPU/(g wheat straw), yeast inoculum 10% (v/v) and substrate concentration 16.7% (w/v). Under the optimal conditions, the total ethanol concentration in SSF of wheat straw pretreated with steam explosion and alkaline peroxide reached 51.5 g/L, and an overall yield of 81.1% was obtained. (c) 2008 Elsevier Ltd. All rights reserved.

Rice hulls used in this study contained 35.62 ± 0.12% cellulose and 11.96 ± 0.73% hemicellulose. Alkaline H2O2 pretreatment and enzymatic saccharification methods were evaluated for conversion of rice hull cellulose and hemicellulose to simple sugars. The yield of sugars from diluted alkaline peroxide pretreated (7.50% H2O2, v/v; pH 11.5; 35 °C; 24 h) rice hulls (15.0%, w/v) after enzymatic saccharification (45 °C, pH 5.0, 72 h) by three commercial enzyme preparations (cellulase, β-glucosidase, and xylanase) using 0.12 ml of each enzyme preparation per g hulls was 428 ± 12 mg/g (90% yield). During the pretreatment, no measurable furfural and hydroxymethyl furfural were produced. The almost complete conversion (96%) of rice hulls to sugars was achieved by saccharifying the liquid and solid fractions separately after alkaline peroxide pretreatment. The concentration of ethanol from alkaline peroxide pretreated, enzyme saccharified rice hull (39 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 35 °C in 24 h was 8.2 ± 0.2 g/l with a yield of 0.49 g/g available sugars (0.21 g/g hulls). The ethanol concentration was 8.0 ± 0.2 g/l with a yield of 0.20 g/g hulls in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 35 °C in 48 h.

Wheat straw used in this study contained 44.24 +/- 0.28% cellulose and 25.23 +/- 0.11% hemicellulose. Alkaline H(2)O(2) pretreatment and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to fermentable sugars. The maximum yield of monomeric sugars from wheat straw (8.6%, w/v) by alkaline peroxide pretreatment (2.15% H(2)O(2), v/v; pH 11.5; 35 degrees C; 24 h) and enzymatic saccharification (45 degrees C, pH 5.0, 120 h) by three commercial enzyme preparations (cellulase, beta-glucosidase, and xylanase) using 0.16 mL of each enzyme preparation per g of straw was 672 +/- 4 mg/g (96.7% yield). During the pretreatment, no measurable quantities of furfural and hydroxymethyl furfural were produced. The concentration of ethanol (per L) from alkaline peroxide pretreated enzyme saccharified wheat straw (66.0 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 37 degrees C in 48 h was 18.9 +/- 0.9 g with a yield of 0.46 g per g of available sugars (0.29 g/g straw). The ethanol concentration (per L) was 15.1 +/- 0.1 g with a yield of 0.23 g/g of straw in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 37 degrees C in 48 h.

To optimize the enzymatic conversion of widely available lignocellulosic biomass-wheat straw (WS), pretreatment facilitating the enzymatic saccharification process was first performed by alkaline peroxide, resulting in a substrate consisting of 60.17% cellulose, 29.53% hemicelluloses, and 4.59% lignin. Using response surface methodology, the combined effects of enzyme loading, substrate concentration, surfactant concentration, and reaction time on hydrolysis yield from enzymatic saccharification of WS were further investigated. The results showed that both enzyme loading and substrate concentration had interactions with surfactant concentration. A quadratic polynomial equation for predicting the hydrolysis yield was developed. The experimental results were in good agreement with predicted values. Therefore, the model could be successfully used to identify the effective combinations of the four factors for predicting hydrolysis yield.

Alkaline peroxide pretreatment for the delignification of rice straw was optimised by varying the concentrations of H2O2 and NaOH and changing the temperature and duration of the pretreatment. Changes in the lignin content, content of total carbohydrates and weight loss were measured during the pretreatments. Maximum delignification of 62% was obtained by pretreating rice straw at 50°C for 5h with 1.5% (w/v) NaOH and 1% (v/v) H2O2, The preferential loss of hemicellulose and lignin from the straw resulted in an increase in the cellulose content of the insoluble residue after pretreatment from 47% (untreated) to 67.79% (treated). The product of this treatment is characterised by having higher cellulose digestibility than untreated rice straw. It also has use as a carbohydrate source in ruminant feed since the in-vivo digestibility by the cow increased from 56.85 % to 76.54% (P < 0.001). The treated rice straw could also be used for commercial process such as the generation of Single Cell Protein. Growth of Sporotrichum pulverulentum on treated rice straw gave a protein product of 24.41 % as compared to 3.8% on untreated rice straw.

The effect of thermal, acid, alkaline and alkaline-peroxide pretreatments on the methane produced by the anaerobic digestion of wheat straw (WS) and sugarcane bagasse (SCB) was studied, using whole slurry and solid fraction. All the pretreatments released formic and acetic acids and phenolic compounds, while 5-hydroxymetilfurfural (HMF) and furfural were generated only by acid pretreatment. A remarkable inhibition was found in most of the whole slurry experiments, except in thermal pretreatment which improved methane production compared to the raw materials (29% for WS and 11% for SCB). The alkaline pretreatment increased biodegradability (around 30%) and methane production rate of the solid fraction of both pretreated substrates. Methane production results were fitted using first order or modified Gompertz equations, or a novel model combining both equations. The model parameters provided information about substrate availability, controlling step and inhibitory effect of compounds generated by each pretreatment.

Two-stage treatments of Caligonum monogoliacum and Tamarix spp. with acidic organosolv and alkaline peroxide were performed. Pre-treatment with ethanol–H 2 O (60/40, v/v) under acid catalyst (0.2 N HCl) at 70 °C for 4 h released 18.7 and 17.8% hemicelluloses from dewaxed C. monogoliacum and Tamarix spp., respectively, Sequential treatment with 2% H 2 O 2 at pH 11.5 for 16 h at 45 °C solubilized 26.2 and 26.5% hemicelluloses from pre-treated C. monogoliacum and Tamarix spp., respectively. Cellulose predominated in the insoluble residues, accounting for 36.7–37.8% of dry materials. It was found that the two alkaline peroxide soluble hemicellulosic preparations contained a much higher amount of xylose (74.1–77.3%) but lower in glucose (7.4–18.6%), galactose (3.0–8.3%), rhamnose (2.3–2.9%), mannose (0.8–2.7%), and arabinose (1.3–1.4%) than those of the two acidic organosolv soluble hemicellulosic fractions in which xylose (31.8–50.8%), glucose (21.4–30.3%), galactose (7.6–24.1%), and rhamnose (5.7–10.1%) were the major sugar components. The content of uronic acids was slightly higher in the two alkaline peroxide soluble hemicellulosic preparations (7.5–8.3%) than the two acidic organosolv soluble hemicellulosic fractions (5.0–6.5%). Furthermore, the studies showed that the two alkaline peroxide soluble hemicellulosic preparations were more linear and acidic, and had a large molecular mass ( M w , 27,220–31,410 g mol −1 ) than the two acidic organosolv soluble hemicellulosic fractions ( M w , 13,820–18,380 g mol −1 ). Lignin content and its composition associated in the four isolated hemicelluloses were determined by alkaline nitrobenzene oxidation and monitored with HPLC. No significant differences in lignin content (5.94–9.82%) and its composition were found. Further comparative study of the four hemicellulosic preparations and two cellulosic fractions was carried by both degraded methods such as acid hydrolysis and thermal analysis and non-degradation techniques such as FT-IR and 13 C-NMR spectroscopy.

A combination of steam explosion (SE) and alkaline peroxide (AP) used to pretreat bamboo was investigated. Steam explosion at 224 °C for 4 min was applied to bamboo, and the pretreated bamboo was delignified by alkaline peroxide. Enzymatic hydrolysis was compared in the pretreated samples. Steam pretreatment led to remarkable hemicellulose solubilization (63.2%). Lignin solubilization (93.1%) was achieved by alkaline peroxide treatment of steam-pretreated bamboo at 80 °C for 1 h in 0.88% (v/v) H2O2, whereas only 33.4% of lignin was solubilized when using raw bamboo. Pretreatment methods resulted in a low degree of polymerization and increased hydrolysis of cellulose. A maximum glucose yield of 90.5% was achieved with a combined steam explosion and alkaline peroxide pretreatment. The surface structure of treated bamboo and the adsorption of enzyme on the substrate were characterized by X-ray photoelectron spectroscopy. Delignification decreased enzyme adsorption and increased enzymatic conversion. SEM analyses indicated that SE-AP pretreatment disrupted lignin networks and exposed crystalline cellulose in bamboo more effectively than SE or AP pretreatment alone.

Furfural residues (FR), the abundant lignocellulosic residues from commercial furfural production, were delignified with alkaline peroxide process and then taken as substrates for ethanol production by simultaneous saccharification and fermentation (SSF). It was apparent that the delignification efficiency was increased with higher chemical addition and temperature, reaching the maximum removal (73.5%) of lignin. The widespread accessible-cellulose in FR favored the enzymatic hydrolysis and achieved the considerable bioconversion (75.7% with 5 FPU + 10 IU/g substrate). The delignification process increased the relative glucose content and then the bioconversion efficiency, closely relating to the increased specific surface area. As the cellulose contents were higher than 60%, the final conversions conversely fell to around 75%, probably due to the insufficient utilization of all active cellulose with low enzyme cocktails addition. Although the SSF bioconversion slightly decreased as the elevated amount of fermentable cellulose, the maximum of ethanol concentration (16.9 g/L) was expectedly obtained.

Alkaline peroxide pretreatment of rapeseed straw was evaluated for conversion of cellulose and hemicellulose to fermentable sugars. After pretreatment, a liquid phase called pretreatment liquid and a solid phase were separated by filtration. The neutralized pretreatment liquids were used in a co-fermentation process, with Saccharomyces cerevisiae and Pichia stipitis. The solid fraction was used for simultaneous saccharification and co-fermentation process in the same vessel. The effects of various operating variables were investigated. Pretreatment with 5% (v/v) H2O2 at 50 °C for 1 h was found to be the optimal pretreatment combination with respect to overall ethanol production. At this condition, 5.73 g ethanol was obtained from pretreatment liquid and 14.07 g ethanol was produced by co-fermentation of solid fraction with P. stipitis. Optimum delignification was observed when 0.5 M MgSO4 was included in the pretreatment mixture, and it resulted in 0.92% increase in ethanol production efficiency.

Pretreatment of rice husk by alkaline peroxide assisted wet air oxidation (APAWAO) approach was investigated with the aim to enhance the enzymatic convertibility of cellulose in pretreated rice husk. Rice husk was presoaked overnight in 1% (w/v) H2O2 solution (pH adjusted to 11.5 using NaOH) (equivalent to 16.67 g H2O2 and 3.63 g NaOH per 100 g dry, untreated rice husk) at room temperature, followed by wet air oxidation (WAO). APAWAO pretreatment resulted in solubilization of 67 wt % of hemicellulose and 88 wt % of lignin initially present in raw rice husk. Some amount of oligomeric glucose (˜8.3 g/L) was also observed in the APAWAO liquid fraction. APAWAO pretreatment resulted in 13-fold increase in the amount of glucose that could be obtained from otherwise untreated rice husk. Up to 86 wt % of cellulose in the pretreated rice husk (solid fraction) could be converted into glucose within 24 hours, yielding over 21 g glucose per 100 g original rice husk. Scanning electron microscopy was performed to visualize changes in biomass structure following the APAWAO pretreatment. Enzymatic cellulose convertibility of the pretreated slurry at high dry matter loadings was also investigated. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011

A two-stage pretreatment method was proposed and tested for deconstruction of recalcitrant Miscanthus. During a 1st pretreatment at 50 degrees C, 1.0-4.0% alkaline peroxide solutions were used to partially remove hemicellulose and lignin. The remaining solids were subjected to a 2nd pretreatment at 121 degrees C with electrolyzed water. Using 15 filter paper units of cellulase per gram cellulose, a digestibility of 95% was achieved by the two-stage method, which was higher than 81% obtained from a 1% H(2)SO(4) pretreatment (200 degrees C, 8 min). A mass balance for the two-stage process showed that 63% hemicellulose and 64% lignin were removed from the Miscanthus samples after the 1st pretreatment. The Scanning Electron Microscopy images and Fourier Transform Infrared Spectroscopy spectra revealed that after the 1st pretreatment, crystalline cellulose fibers were partially exposed and the linkages between residual lignin and hemicellulose disappeared. After the 2nd pretreatment, cellulose fibers were completely exposed even with cracks developed.

Pretreatment of corn stover with alkaline peroxide (AP) at pH 11.5 resulted in reduction of lignin content in the residual solids as a function of increasing batch temperature. Scanning electron microscopy of these materials revealed notably more textured surfaces on the plant cell walls as a result of the delignifying pretreatment. As expected, digestion of the delignified samples with commercial cellulase preparations showed an inverse relationship between the content of lignin present in the residual solids after pretreatment and the extent of both glucan and xylan conversion achievable. Digestions with purified enzymes revealed that decreased lignin content in the pretreated solids did not significantly impact the extent of glucan conversion achievable by cellulases alone. Not until purified xylanolytic activities were included with the cellulases were significant improvements in glucan conversion realized. In addition, an inverse relationship was observed between lignin content after pretreatment and the extent of xylan conversion achievable in a 24-h period with the xylanolytic enzymes in the absence of the cellulases. This observation, coupled with the direct relationship between enzymatic xylan and glucan conversion observed in a number of cases, suggests that the presence of lignins may not directly occlude cellulose present in lignocelluloses but rather impact cellulase action indirectly by its association with xylan.

The enzymatic digestibility of steam-exploded Douglas-fir wood chips (steam exploded at 195°C, 4.5 min, and 4.5% (w/w) SO2) was significantly improved using an optimized alkaline peroxide treatment. Best hydrolysis yields were attained when the steam-exploded material was post-treated with 1% hydrogen peroxide at pH 11.5 and 80°C for 45 min. This alkaline peroxide treatment was applied directly to the water-washed, steam-exploded material eliminating the need for independent alkali treatment with 0.4% NaOH, which has been traditionally used to post-treat wood samples to try to remove residual lignin. Approximately 90% of the lignin in the original wood was solubilized by this novel procedure, leaving a cellulose-rich residue that was completely hydrolyzed within 48 h, using an enzyme loading of 10 FPU/g cellulose. About 82% of the originally available polysaccharide components of the wood could be recovered. The 18% of the carbohydrate that was not recovered was lost primarily to sugar degradation during steam explosion. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 678–684, 2002; DOI 10.1002/bit.10159

A spin-trapping EPR technique has been employed to explore the generation of hydroxyl radicals from reactions between a series of first row transition metal ions and aqueous hydrogen peroxide at pH 10, and with a range of chelating agents (EDTA, DTPMP and the readily biodegradable ligands S,S-EDDS and IDS). In the absence of these chelating agents only Cu(II) generates a significant level of hydroxyl radicals; in their presence with Cu(II) EDTA and IDS give similar behaviour whereas EDDS and DTPMP inhibit hydroxyl radical generation. For Fe(II), EDTA, DTPMP and IDS significantly enhance ( radical)OH production under these conditions whereas EDDS does not. Results from model cellulose damage experiments broadly confirm the findings for copper, though experiments with Fe(II) lead to somewhat contrasting results. Our findings are discussed in terms of binding constants and implications for alkaline peroxygen bleaching systems.

Specific oligonucleotide probes targeted to sites on the 16S rRNA of Ruminococcus albus 8, Ruminococcus flavefaciens FD-1, and Fibrobacter succinogenes S85 and a domain Bacteria probe were used to study bacterial interactions during the fermentation of cellulose and alkaline hydrogen peroxide-treated wheat straw in monocultures, dicultures, and tricultures. Results showed that R. albus 8 inhibited the growth of R. flavefaciens FD-1 when grown as a diculture with cellulose or alkaline hydrogen peroxide-treated wheat straw as the carbon source. In dicultures containing R. albus 8 and F. succinogenes S85 grown on cellulose or alkaline hydrogen peroxide-treated wheat straw, competition was not detected. R. flavefaciens FD-1 outcompeted F. succinogenes S85 when cellulose was used as the carbon source. In tricultures with cellulose as the carbon source, R. flavefaciens FD-1 was inhibited, R. albus 8 appeared to dominate during the early phase of degradation (12 to 48 h), while F. succinogenes S85 became predominant during the later phase of degradation (60 to 70 h). When alkaline hydrogen peroxide-treated wheat straw was used as a growth substrate, F. succinogenes S85 showed better growth than either R. albus 8 or R. flavefaciens FD-1. However, R. flavefaciens FD-1 was present in small numbers throughout the incubation period, unlike the growth patterns when cellulose was the carbon source.

Approximately one-half of the lignin and most of the hemicellulose present in agricultural residues such as wheat straw and corn stover are solubilized when the residue is treated at 25 degrees C in an alkaline solution of hydrogen peroxide. The delignification reaction is most efficient when the ratio of hydrogen peroxide to substrate is at least 0.25 (w/w) and the pH is 11.5. The supernatant fraction from a given pretreatment, after addition of makeup peroxide and readjustment of the pH, can be recycled to treat at least six additional batches of substrate, resulting in a substantial concentration of hemicellulose and soluble lignin degradation products. Hydrolysis of the insoluble fraction with Trichoderma reesei cellulase after alkaline peroxide treatment yields glucose with almost 100% efficiency, based upon the cellulose content of the residue before treatment. These data indicate that alkaline peroxide pretreatment is a simple and efficient method for enhancing the enzymatic digestibility of lignocellulosic crop residues to levels approaching the theoretical maximum.