Hydrogen Peroxide-acetic Acid Pretreatment Research Articles

Effect of peracetic acid generation in hydrogen peroxide-acetic acid pretreatment on production of xylooligosaccharides from poplar by organic acid hydrolysis

Hydrogen peroxide-acetic acid (HPAA) compositions affect the peracetic acid generation and subsequent delignification of lignocellulosic materials. However, the effects of HPAA compositions on lignin removal and poplar hydrolyzability after HPAA pretreatment are not fully elucidated yet. In this work, different volume ratios of HP to AA were used to pretreat poplar, AA and lactic acid (LA) hydrolysis of delignified poplar to produce XOS was compared. Peracetic acid was mainly produced in 1 h of HPAA pretreatment. HPAA with HP to AA ratio of 8:2 (HP8AA2) generated 4.4% peracetic acid and removed 57.7% of lignin at 2 h. Furthermore, XOS production from HP8AA2-pretreated poplar by AA and LA hydrolysis was increased by 97.1% and 14.9% compared to those from raw poplar, respectively. After alkaline incubation, the glucose yield of HP8AA2-AA-pretreated poplar increased from 40.1% to 97.1%. The study results indicated that HP8AA2 was conducive to XOS and monosaccharides production from poplar..

Lignin removal improves xylooligosaccharides production from poplar by acetic acid hydrolysis

Organic acid hydrolysis is a potential method for xylooligosaccharides (XOS) production from lignocelluloses. However, the effect of lignin content on XOS production using organic acid hydrolysis remains unclear. In this work, the effect of delignification on XOS production from poplar by acetic acid (AC) hydrolysis was investigated. Hydrogen peroxide-acetic acid (HPAC) pretreatment catalyzed by 0–200 mM H2SO4 (HPAC0–HPAC200) removed 21.6–86.5% of lignin in poplar. HPAC pretreatment increased the xylan accessibility to AC solution, thus increasing the xylan removal during AC hydrolysis. An appropriate delignification (61.7%) resulted in the highest XOS yield of 37.4% by AC hydrolysis, increased by 29.9% compared to the optimal XOS yield (28.8%) from raw poplar. After alkaline post-incubation, the glucose yield of poplar residue rose from 57.1% to 78.6%. This work developed a delignification process to efficiently improve XOS and monosaccharides production from poplar.

Highly selective delignification of poplar by hydrogen peroxide-ethyl acetate pretreatment at room temperature

Highly selective delignification of lignocellulose with green solvent at mild conditions is a challenge. Previously, hydrogen peroxide-acetic acid (HPAA) was used as a green solvent in pretreatment exhibits excellent selective delignification capacity at a low reaction temperature (<80 °C). However, the release of oxygen can increase the pressure of the hydrogen peroxide-acetic acid (HPAA) pretreatment system and the risk of explosion. To overcome this problem, a novel hydrogen peroxide-ethyl acetate (HPEA) pretreatment was developed to remove poplar lignin, aiming at improving the pretreatment safety and saccharification efficiency. After HPEA pretreatment at room temperature for three days, 97.2% of poplar lignin was removed and 92.1% of original carbohydrate was retained. The glucose and xylose yields of HPEA-pretreated poplar reached 90.6% and 81.5% by a cellulase loading of 5 FPU/g dry matter, respectively. Compared with HPAA pretreatment, HPEA pretreatment reduced more than 93% of pressure in pretreatment system and largely increased pretreatment safety. The results indicates that HPEA pretreatment exhibited stronger delignification capacity, high carbohydrate retention, high safety, and strong enhancement of digestibility of poplar. This work provides a safe pretreatment to selectively remove lignin at mild conditions for efficient saccharification of poplar.

Combined acetic acid and enzymatic hydrolysis for xylooligosaccharides and monosaccharides production from poplar

Efficient production of xylooligosaccharides (XOS) from lignocellulosic biomass without preliminary xylan isolation is challenging. Previously, organic acid has been used to produce XOS from lignocelluloses without xylan isolation. However, the knowledge about XOS production from the residual xylan in acid-hydrolyzed lignocelluloses is still unclear. In this study, acetic acid (AC) hydrolysis of poplar was used to produce XOS, then AC-hydrolyzed poplar was delignified by hydrogen peroxide-acetic acid (HPAC) solution. The AC-HPAC-pretreated poplar was sequentially hydrolyzed by xylanase and cellulase to produce XOS and monosaccharides. The results showed that the XOS yield of poplar after AC hydrolysis was 31.6% (based on the xylan in raw poplar). A high lignin removal (94.8%) of AC-hydrolyzed poplar was obtained by HPAC pretreatment. The highest XOS yield based on residual xylan in AC-HPAC-pretreated poplar by xylanase was 17.5%, and finally a total XOS yield of 36.5% based on xylan in raw poplar was achieved. The highest glucose yield was 88.0% with 20 FPU/g dry mass cellulase and 1.0 mg/mL Tween 80. Finally, 65.1 g of XOS was obtained from 1,000 g of poplar through this combined process including AC and xylanase hydrolysis, increased by 2.2 times compared with that from xylanase hydrolysis without AC hydrolysis. This work greatly improves the XOS production from poplar and provides a novel strategy to efficiently transform poplar carbohydrates into XOS and monosaccharides.

Production of monosaccharides from poplar by a two-step hydrogen peroxide-acetic acid and sodium hydroxide pretreatment

Hydrogen peroxide-acetic acid (HPAC) pretreatment can selectively remove lignin from biomass. However, high concentration of HPAC increases the cost of pretreatment and the risk of explosion. In this work, HPAC pretreatment was optimized and the function of the second-step sodium hydroxide pretreatment in the reduction of HPAC dosage and the increased of saccharification of poplar was investigated. The results showed that pretreatment of poplar with 75 % HPAC at 80 ˚C for 2 h with 100 mM H2SO4 as a catalyst removed 94.1 % of lignin, and the glucose and xylose yields of HPAC-pretreatd poplar by cellulase were 78.5 % and 66.3 %, respectively. After post-treatment with 1 % sodium hydroxide, the lignin removal in 50 % HPAC (80 ˚C, 1 h)-pretreated poplar increased from 47.7% to 86.7 % with the acetyl groups were completely removed. After sodium hydroxide pretreatment, the yields of glucose and xylose of 50 % HPAC-pretreated poplar largely increased from 37.8 % and 28.8 % to 79.4 % and 80.0 %, respectively. The data here indicated that alkaline treatment reduced about 33 % HPAC loading and 50 % reaction time without the decrease of hydrolysis yield. This work provided a novel strategy to efficient production of fermentable sugars from poplar with less HPAC loading and higher safety at mild conditions.

Optimization of zero-waste hydrogen peroxide - Acetic acid pretreatment for sequential ethanol and methane production

In this study, the development of an environmentally friendly version of hydrogen peroxide – acetic acid (HPAC) pretreatment was investigated and optimized with two different approaches as maximum biofuel production optimization and cost optimization. Central composite design and response surface method were used for the experimental design and data analysis, respectively. In the experimental design, investigated HPAC pretreatment parameters were 50–100 °C reaction temperature, 6–24 h reaction time, 0–2 wt% HAc and 0–2 wt% H2O2. Significant ethanol production enhancement was observed only for the samples pretreated at 100 °C. This increase was due to the enhanced enzyme accessibility by the surface area increment and delignification, which were also revealed in SEM imaging and FTIR analysis. Maximum ethanol production was observed in 2% H2O2, 0% HAc, 24 h, and 100 °C pretreatment conditions as 81.65 mg EtOH/g total solid (TS) (103.49 L EtOH/tonne TS), corresponding 49.55% of the theoretical ethanol yield. Maximum methane production, on the other hand, was observed in 2% HAc, 0% H2O2, 100 °C, 6 h conditions as 363.82 mL CH4/g VS. In terms of net energy production, cost optimum pretreatment (1.87% HAc, 0% H2O2, 50 °C, and 6 h) was found be the most beneficial condition with 67.5% energy recovery.

Hydrolysis pattern analysis of xylem tissues of woody plants pretreated with hydrogen peroxide and acetic acid: rapid saccharification of softwood for economical bioconversion

BackgroundWoody plants with high glucose content are alternative bioresources for the production of biofuels and biochemicals. Various pretreatment methods may be used to reduce the effects of retardation factors such as lignin interference and cellulose structural recalcitrance on the degradation of the lignocellulose material of woody plants.ResultsA hydrogen peroxide-acetic acid (HPAC) pretreatment was used to reduce the lignin content of several types of woody plants, and the effect of the cellulose structural recalcitrance on the enzymatic hydrolysis was analyzed. The cellulose structural recalcitrance and the degradation patterns of the wood fibers in the xylem tissues of Quercus acutissima (hardwood) resulted in greater retardation in the enzymatic saccharification than those in the tracheids of Pinus densiflora (softwood). In addition to the HPAC pretreatment, the application of supplementary enzymes (7.5 FPU cellulase for 24 h) further increased the hydrolysis rate of P. densiflora from 61.42 to 91.94% whereas the same effect was not observed for Q. acutissima. It was also observed that endoxylanase synergism significantly affected the hydrolysis of P. densiflora. However, this synergistic effect was lower for other supplementary enzymes. The maximum concentration of the reducing sugars produced from 10% softwood was 89.17 g L−1 after 36 h of hydrolysis with 15 FPU cellulase and other supplementary enzymes. Approximately 80 mg mL−1 of reducing sugars was produced with the addition of 7.5 FPU cellulase and other supplementary enzymes after 36 h, achieving rapid saccharification.ConclusionHPAC pretreatment removed the interference of lignin, reduced structural recalcitrance of cellulose in the P. densiflora, and enabled rapid saccharification of the woody plants including a high concentration of insoluble substrates with only low amounts of cellulase. HPAC pretreatment may be a viable alternative for the cost-efficient production of biofuels or biochemicals from softwood plant tissues.

Effect of sulfuric acid on production of xylooligosaccharides and monosaccharides from hydrogen peroxide-acetic acid-pretreated poplar

Lignin is one of the main obstacles for enzymatic hydrolysis, which can be selectively removed by hydrogen peroxide-acetic acid pretreatment (HPAC). In this work, the effects of sulfuric acid concentration on chemical composition, structural features, physical properties and enzymatic digestibility of HPAC pretreated poplar were investigated. The increased H2SO4 dosage enhanced the lignin removal of HPAC-pretreated poplar, resulting in the increased accessibility and decreased hydrophobicity. A satisfying glucose yield (91.84%) was obtained from HPAC pretreated poplar (100 mM H2SO4) at 5 FPU/g DM of cellulase loading with the addition of xylanase (30 U/g DM) and Tween 80 (3 g/L). The increment of H2SO4 concentration promoted the yield of xylooligosaccharides from 0.69% to 20.45% and monosaccharides from 5.76% to 92.89% respectively by two-step enzymatic hydrolysis. This work demonstrated that HPAC pretreatment played a critical role in efficient utilization of poplar carbohydrates by enzymatic hydrolysis.

Hydrolysis Patterns of Xylem Tissues of Hardwood Pretreated With Acetic Acid and Hydrogen Peroxide

The structural recalcitrance of lignocellulose limits its enzymatic hydrolysis, which leads to inefficient enzyme usage and inhibition of saccharification, depending on the pretreatment method. Research on the structural properties of xylem tissues of hardwood and their effect on enzymatic saccharification is necessary to achieve cost-effective biofuel production via improved enzyme cocktail preparation. Oak wood (Quercus acutissima) was pretreated and delignified with a hydrogen peroxide-acetic acid (HPAC) solution. Cellulose was found to undergo significant swelling in the lumen of the wood fiber, and it was sorted into readily hydrolysable (72.9%), mid-hydrolysable (8.2%), and hardly hydrolysable (18.9%) cellulose forms. Oak wood has been shown to be strongly retarded among the various types of hardwoods. The recalcitrance of the xylem tissues, such as wood fibers, tracheids, vessel elements, and ray parenchyma cells, was determined through analysis of the hydrolysis rates. It was found to increase in the following order: ray parenchyma cells < tracheids < wood fibers or vessel elements < tracheids < wood fibers. The wood fibers were almost enzymatically fragmented into pieces approximately 90 μm in length at crack sites in 6 h. The wood fibers were digested faster in the S3 or S2 wall than in the primary wall. The result indicated that the primary wall may be a structural retardation factor in the hardwood as sorted to the hardly hydrolysable cellulose. In presence of 10% substrate supplemented with enzymes to reduce the structural recalcitrance (xylanase and lytic polysaccharide monoxygenase) and end-product inhibitions (beta-glucosidase), the hydrolysis rate was increased by 55.21%. Ethanol fermentation exhibited a higher efficiency when a single substrate (Q. acutissima) rather than a mixture of various hardwoods was used. Of all the xylem tissues of hardwood that were delignified by HPAC pretreatment, wood fiber was found to be a structural retardation factor owing to the recalcitrance its primary wall. Thus, enzyme preparation can enable the rapid and efficient hydrolysis for the commercialization of bioethanol from hardwood.

Production of xylooligosaccharides and monosaccharides from hydrogen peroxide-acetic acid-pretreated poplar by two-step enzymatic hydrolysis

The severe pretreatment of poplar makes xylan difficult to utilize efficiently. In this work, poplar was pretreated by hydrogen peroxide–acetic acid (HPAC) with H2SO4 as catalyst to remove lignin, and the solid residues were used to produce xylooligosaccharides (XOS) and monosaccharides by two-step xylanase and cellulase hydrolysis. The results indicated that higher H2SO4 concentrations in the HPAC pretreatment of poplar afforded stronger lignin removal ability. An increased XOS yield of 19.8% was obtained from 200 mM H2SO4-catalyzed poplar by xylanase and the XOS purity was high, with a very low xylose/XOS ratio of 0.14. Higher glucose (75.2%) and xylose (61.4%) yields were obtained from the HPAC-pretreated poplar using 50 mM H2SO4 as catalyst. Finally, 16.9 g XOS and 296.4 g glucose were produced from 1 kg poplar by xylanase and cellulase. This study provides a method for producing functional XOS and monosaccharides from poplar using a simple reduced-pollution strategy.

A strategy for sequential fermentation by Saccharomyces cerevisiae and Pichia stipitis in bioethanol production from hardwoods

Climate change due to global warming has led to the expansion of deciduous forests. Increased product yields from hardwood provide an opportunity for the exploitation of biomass resources, such as bioethanol. In this study, the enzymatic hydrolysis of various hardwoods pretreated using the hydrogen peroxide–acetic acid (HPAC) method was evaluated. Glucose and xylose were fermented sequentially to improve the bioethanol production from hardwood. The HPAC pretreatment significantly reduced lignin and improved the hydrolysis efficiency compared with no treatment. The enhanced hydrolysis efficiency contributed to an increase in the bioethanol productivity, which was similar to that of simultaneous saccharification and fermentation, by reducing the processing time of separate hydrolysis and fermentation. The sequential fermentation of glucose and xylose via Saccharomyces cerevisiae and Pichia stipitis, respectively, improved ethanol production by approximately 12% over conventional fermentation used with glucose alone. The results suggest that sequential fermentation can improve bioethanol production from hardwood.

Influence of size reduction treatments on sugar recovery from Norway spruce for butanol production

This study investigated whether the effectiveness of pretreatment is limited by a size reduction of Norway spruce wood in biobutanol production. The spruce was milled, chipped, and mashed for hydrogen peroxide-acetic acid (HPAC) and dilute acid (DA) pretreatment. Sugar recoveries from chipped and mashed spruce after enzymatic hydrolysis were higher than from milled spruce, and the recoveries were not correlated with the spruce fiber length. HPAC pretreatment resulted in almost 100% glucose and 88% total reducing sugars recoveries from chipped spruce, which were apparently higher than DA pretreatment, demonstrating greater effectiveness of HPAC pretreatment on sugar production. The butanol and ABE yield from chipped spruce were 126.5 and 201.2 g/kg pretreated spruce, respectively. The yields decreased with decreasing particle size due to biomass loss in the pretreatment. The results suggested that Norway spruce chipped to a 20 mm length is applicable to the production of platform sugars for butanol fermentation.

Evaluation of biomass quality in short-rotation bamboo (Phyllostachys pubescens) for bioenergy products

BackgroundIn order to improve the availability of biomass, the concept of growing high yield biomass with short rotations and intensive culture has been introduced. Bamboo has become a feedstock of potential interest for future energy production due to its high productivity and short rotation time. The growth age of biomass is an important factor affecting the efficiency of bioconversion and pretreatment for bioenergy production. In this regard, more information is required on the morphology and chemical composition of bamboo for short-rotation biomass production. In this study, we used a compositional assay to compare a bamboo of two different growth ages.ResultsBamboo of two different ages showed characteristics patterns of morphology, chemical composition, and bioconversion. In young-age (2-month-old) bamboo, the pattern of tissue organization was similar to that of old-age (3-year-old) bamboo, indicating that the former had reached its full height. There were significant differences between young-age and old-age bamboo in terms of chemical composition. The glucose contents in old-age bamboo did not differ significantly among its internodes. For young-age bamboo, the lignin contents were 14.6–18.3%, whereas those of old-age bamboo were considerably higher, ranging from 25.4 to 27.1% with increasing syringyl-to-guaiacyl ratio. The yield of total sugars following enzymatic hydrolysis of young-age bamboo was approximately eight times. However, following hydrogen peroxide–acetic acid pretreatment, the results of separate hydrolysis and fermentation and simultaneous saccharification and fermentation did not differ significantly between young- and old-age bamboo. However, ethanol production was higher in 2-month old than in 3-year old from initial raw biomass.ConclusionOur data show that the production of total sugar from raw material was high in young bamboo with low lignin content. With respect to short-rotation biomass, bamboo culm harvested after termination of height growth is more appropriate for use as a biomass resource to achieve a high yield for bioconversion process.

Isoprene Production on Enzymatic Hydrolysate of Peanut Hull Using Different Pretreatment Methods.

The present study is about the use of peanut hull for isoprene production. In this study, two pretreatment methods, hydrogen peroxide-acetic acid (HPAC) and popping, were employed prior to enzymatic hydrolysis, which could destroy the lignocellulosic structure and accordingly improve the efficiency of enzymatic hydrolysis. It is proven that the isoprene production on enzymatic hydrolysate with HPAC pretreatment is about 1.9-fold higher than that of popping pretreatment. Moreover, through High Performance Liquid Chromatography (HPLC) analysis, the amount and category of inhibitors such as formic acid, acetic acid, and HMF were assayed and were varied in different enzymatic hydrolysates, which may be the reason leading to a decrease in isoprene production during fermentation. To further increase the isoprene yield, the enzymatic hydrolysate of HPAC was detoxified by activated carbon. As a result, using the detoxified enzymatic hydrolysate as the carbon source, the engineered strain YJM21 could accumulate 297.5 mg/L isoprene, which accounted for about 90% of isoprene production by YJM21 fermented on pure glucose (338.6 mg/L). This work is thought to be the first attempt on isoprene production by E. coli using peanut hull as the feedstock. More importantly, it also shows the prospect of peanut hull to be considered as an alternative feedstock for bio-based chemicals or biofuels production due to its easy access and high polysaccharide content.

Lignocellulose conversion for biofuel: a new pretreatment greatly improves downstream biocatalytic hydrolysis of various lignocellulosic materials.

BackgroundLignocellulosic biomass is an attractive renewable resource for future liquid transport fuel. Efficient and cost-effective production of bioethanol from lignocellulosic biomass depends on the development of a suitable pretreatment system. The aim of this study is to investigate a new pretreatment method that is highly efficient and effective for downstream biocatalytic hydrolysis of various lignocellulosic biomass materials, which can accelerate bioethanol commercialization.ResultsThe optimal conditions for the hydrogen peroxide–acetic acid (HPAC) pretreatment were 80 °C, 2 h, and an equal volume mixture of H2O2 and CH3COOH. Compared to organo-solvent pretreatment under the same conditions, the HPAC pretreatment was more effective at increasing enzymatic digestibility. After HPAC treatment, the composition of the recovered solid was 74.0 % cellulose, 20.0 % hemicelluloses, and 0.9 % lignin. Notably, 97.2 % of the lignin was removed with HPAC pretreatment. Fermentation of the hydrolyzates by S. cerevisiae resulted in 412 mL ethanol kg−1 of biomass after 24 h, which was equivalent to 85.0 % of the maximum theoretical yield (based on the amount of glucose in the raw material).ConclusionThe newly developed HPAC pretreatment was highly effective for removing lignin from lignocellulosic cell walls, resulting in enhanced enzymatic accessibility of the substrate and more efficient cellulose hydrolysis. This pretreatment produced less amounts of fermentative inhibitory compounds. In addition, HPAC pretreatment enables year-round operations, maximizing utilization of lignocellulosic biomass from various plant sources.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0419-4) contains supplementary material, which is available to authorized users.