Pretreated Wheat Straw Research Articles

Combination of ensiling and fungal delignification as effective wheat straw pretreatment.

BackgroundUtilization of lignocellulosic feedstocks for bioenergy production in developing countries demands competitive but low-tech conversion routes. White-rot fungi (WRF) inoculation and ensiling are two methods previously investigated for low-tech pretreatment of biomasses such as wheat straw (WS). This study was undertaken to assess whether a combination of forced ensiling with Lactobacillus buchneri and WRF treatment using a low cellulase fungus, Ceriporiopsissubvermispora, could produce a relevant pretreatment effect on WS for bioethanol and biogas production.ResultsA combination of the ensiling and WRF treatment induced efficient pretreatment of WS by reducing lignin content and increasing enzymatic sugar release, thereby enabling an ethanol yield of 66 % of the theoretical max on the WS glucan, i.e. a yield comparable to yields obtained with high-tech, large-scale pretreatment methods. The pretreatment effect was reached with only a minor total solids loss of 5 % by weight mainly caused by the fungal metabolism. The combination of the biopretreatments did not improve the methane potential of the WS, but improved the initial biogas production rate significantly.ConclusionThe combination of the L. buchneri ensiling and C. subvermispora WRF treatment provided a significant improvement in the pretreatment effect on WS. This combined biopretreatment produced particularly promising results for ethanol production.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0437-x) contains supplementary material, which is available to authorized users.

Evaluation of a pilot-scaled paddle dryer for the production of ethanol from lignocellulose including inhibitor removal and high-solids enzymatic hydrolysis

The advantage of using paddle dryers (PD) in the production of sugars and 2nd generation ethanol from pretreated wheat straw was investigated. This machinery was employed in order to detoxify steam-exploded substrates and to mix different slurries in the hydrolysis step. The obtained hydrolysate was fermented by the yeast Saccharomyces cerevisiae. Acetic acid and furfural were reduced up to 11 and 26 fold respectively in the detoxified substrate. When fermentation was carried out at low solid suspension, the use of PD was as effective as water extraction in detoxifying exploded biomass, giving ethanol yields of 90% at 0.05 solid/liquid ratio (S/L) and 80% at 0.10S/L. Moreover, by using PD the cellulose conversion yield was significantly improved in the hydrolysis step: when operating at higher S/L (0.4), the hydrolysis efficiency was twice the one achieved by using a bioreactor with a Rushton stirrer.

Improvement of wheat straw hydrolysis by cellulolytic blends of two Penicillium spp.

Co-culture of fungal strains Penicillium janthinellum EMS-UV-8 (E), Penicillium funiculosum strain P (P) and Aspergillus sp. strain G (G) and blending of their crude cellulase were evaluated for improvements in cellulase activities as well as for enhanced hydrolysis of dilute acid pretreated wheat straw (PWS). The blending of crude enzymes of P and E enhanced the hydrolysis of PWS more effectively due to synergism in cellulolytic enzyme activities. Here, three types of blends were made on the basis of equal FPUs, equal protein content or fixed volume containing different proportions of individual enzymes, the former blend hydrolyzed 42.6% of PWS due to the 98%,62%, 64% and 34% synergistic enhancement in endo-glucanase, cellulase (FPU), β-glucosidase and xylanase activities, respectively. Hydrolysis at 10% solid loading of PWS in roller bottle reactor with this blend further enhanced hydrolysis yield to 74% within 24 h, which was much better than the corresponding hydrolysis yields of individual (38.1% by E and 61.5% by P) or the commercial enzyme (62.3%). This study proved that synergistic blends of cellulases from two Penicillium spp. are cost-effective tools for efficient wheat straw hydrolysis for on-site biofuel production.

Imidazole: Prospect Solvent for Lignocellulosic Biomass Fractionation and Delignification

The future widespread production of biomass-derived fuels, chemicals, and materials requires cost-effective processing of sustainable feedstock. The use of imidazole as a solvent for biomass creates a novel approach that helps to accomplish this idea in a green fashion. This work proposes imidazole as a novel solvent for wheat straw pretreatment, which allowed the production of cellulose- and hemicellulose-rich fractions and added-value products from depolymerization of lignin. Various temperatures (110, 140, and 170 °C) and processing times (1, 2, and 4 h) of pretreatment were investigated. Both cellulose and hemicellulose recovery were highly dependent on reaction temperature. The best result for the recovery of cellulose-rich material was obtained at 170 °C for 2 h, achieving 62.4% w·w–1, whereas native wheat straw is composed by only 38.8% w·w–1 cellulose. For the same conditions, optimal results were also obtained regarding the enzymatic hydrolysis yield (99.3% w·w–1 glucan to glucose yield) in cellu...

Effects of extracellular proteome on wheat straw pretreatment during solid-state fermentation of Phlebia radiata ATCC 64658

Biological pretreatment of lignocellulosic biomass potentially offers a less energy intensive alternative to chemical pretreatment for the reduction of recalcitrance towards cellulolytic enzymes, but possesses some disadvantages, including a slow rate and loss of polysaccharides. This study characterizes the biodegradation of wheat straw by Phlebia radiata, a white rot fungus capable of secreting three major classes of ligninolytic enzymes: lignin peroxidase, manganese peroxidase, and laccase under natural conditions. We investigated the correlation between synergistic action of fungal enzymes and characteristics of the pretreated biomass. The results showed a sequential expression of enzymes over the course of a three-week pretreatment, with members of the peroxidase family being expressed in week one, followed by laccase expression starting in week two which continued until the course of pretreatment. This highlights the synergy of ligninolytic enzymes in the selective degradation pattern for wheat straw. 1H–13C HSQC NMR spectroscopy results demonstrated reduced amounts of syringyl (S) and hydroxyphenyl (H) lignin after pretreatment. Moreover, the reduction in H lignin was also seen in Pyrolysis – GC/MS and FT-IR results. This strongly suggests that this unique lignin modification pattern is associated with P. radiata extracellular proteome, as expressed during the solid-state fermentation (pretreatment) of wheat straw.

Steam Explosion for Wheat Straw Pretreatment for Sugars Production

AbstractDevelopment of biofuels such as lignocellulosic ethanol represents a sustainable alternative in the transport sector. Wheat straw is a promising feedstock for bioethanol production in Europe due to its large production and high carbohydrates content. In a process to produce cellulosic ethanol, previous to the enzymatic hydrolysis to obtain fermentable sugars and the subsequent fermentation, a pretreatment step to break down the recalcitrance of lignocellulose fiber is essential. In this work, a range of steam explosion pretreatment conditions were evaluated according to different parameters: sugars recovery, degradation products generation, and enzymatic hydrolysis yields. Moreover, the enzymatic hydrolysis process was also studied at high substrate loadings, since operating at high solids loading is crucial for large scale development of ethanol production. Pretreatment at 200°C - 10 min resulted in higher enzymatic hydrolysis yield (91.7%) and overall glucose yields (35.4 g glucose/100 g wheat straw) but also higher production of toxic compound. In turn, the characteristics of the pretreated wheat straw at lower severity (Log R0=3.65) correspond to 190°C and 10 min, with minimal sugars degradation and toxics formation indicated a great potential for maximizing total sugars production by using optimal enzyme combinations including accessory enzymes in the enzymatic hydrolysis step.

Effect of Alkali Treatment of Wheat Straw on Adsorption of Cu(II) under Acidic Condition

The convenient and feasible pretreatment method of alkali treatment is very common in the degradation process of wheat straw. However, its utilization in the pretreatment of wheat straw as alternative adsorbents for aqueous heavy metals remediation is rarely reported. The present study investigated the removal efficiency of Cu(II) ions using wheat straw with alkali pretreatment. The condition of alkali treatment on wheat straw was optimized with the adsorption capacity of Cu(II) as indicator using single-factor experiments. The influences of wheat straw dosages, pH values, contact time, and temperatures on adsorption performance for both untreated wheat straw (UWS) and alkali-treated wheat straw (AWS) were investigated. Results showed that the relatively large removal rate of Cu(II) could be obtained, and chemical behavior occurred during the adsorption process. Characteristic analysis found that the major function of alkali treatment to wheat straw was to introduce the hydroxy group, which resulted in the increase of -C-O- group. Although the adsorption capacity is not as high as the one of ligands supported adsorbents, the method is easy to operate and has a wide range of application; at the same time, it could realize both purposes of treating heavy metal pollution and solid wastes.

Performance evaluation of various bioreactors for methane fermentation of pretreated wheat straw with cattle manure

AbstractThis paper examines the performance results of configured semi-continuous mesophilic bioreactors for methane fermentation of pretreated wheat straw co-digested with cattle manure. The semi-continuous process was carried out in three different types of bioreactors, i.e. continuous stirred tank reactor (CSTR), fixed film reactor (FFR), and conventional floating drum reactor (CR), with an organic loading rate of 2.2 kg of volatile solids (VS)/day. The observed results revealed that the configuration of the FFR increased the methane production yield by 41.1%. However, the configuration of the CSTR had only a marginal effect on enhancement of methane production yield (yield increased only by 10.6%) compared to the CR. The VS removal for digesters did not vary much at the same organic loading rate. The study revealed that the pretreated wheat straw with the FFR had yield methane production of 0.342 m

NaOH Pretreatment of Wheat Straw at a Mesophilic Temperature: Effect on Hydrolysis and Loss of Organic Carbon

NaOH Pretreatment of Wheat Straw at a Mesophilic Temperature: Effect on Hydrolysis and Loss of Organic Carbon

Use of Wheat Straw for Extracellular Cellulase Production from Aspergillus niger F8Isolated from Compost

An extracellular cellulase producing celluloytic Aspergillus niger F8 was isolated from compost sample expressing maximum cellulase activity of 6.75 IU/ml on basal salt medium, pH 4.5, temperature 30°C and inoculum size 10% with 1% substrate concentration on 7 days of incubation. 358.70% increase in enzyme activity was observed after optimisation of parameters under submerged fermentation. Further, enhancement in enzyme activity was done under solid-state fermentation using alkali+steam pretreated wheat straw. A. niger F8 exhibited enzyme activity of 71.22 U/g with pretreated (alkali+steam) biomass. It is a cost-effective enzyme production approach of utilising cheap and abundant lignocellulosic agricultural waste as carbon source.

The effect of adding urea, manganese and linoleic acid to wheat straw and wood chips on lignin degradation by fungi and subsequent in vitro rumen degradation

The aim of this study was optimizing Ceriporiopsis subvermispora and Lentinula edodes pre-treatment of wheat straw and wood chips by adding urea, manganese and linoleic acid. Optimization was defined as more lignin degradation and an increase in in vitro gas production (IVGP), which is a model for rumen degradation, in comparison to fungal treatment without additives. First urea, manganese and linoleic acid were added separately to C. subvermispora or L. edodes treatment of wheat straw and wood chips. Only manganese and linoleic acid addition improved lignin degradation and IVGP compared to the same treatment without additives. Mn (150μg/g wheat straw) influenced C. subvermispora treatment most. A combination of manganese and linoleic acid was also applied since both act on manganese peroxidase. This combination did indeed increase lignin degradation in wheat straw by C. subvermispora, but IVGP was not changed. None of the additions had a significant effect on the other fungus–substrate combinations tested here.

Co-Utilization of Glucose and Xylose for Enhanced Lignocellulosic Ethanol Production with Reverse Membrane Bioreactors.

Integrated permeate channel (IPC) flat sheet membranes were examined for use as a reverse membrane bioreactor (rMBR) for lignocellulosic ethanol production. The fermenting organism, Saccharomyces cerevisiae (T0936), a genetically-modified strain with the ability to ferment xylose, was used inside the rMBR. The rMBR was evaluated for simultaneous glucose and xylose utilization as well as in situ detoxification of furfural and hydroxylmethyl furfural (HMF). The synthetic medium was investigated, after which the pretreated wheat straw was used as a xylose-rich lignocellulosic substrate. The IPC membrane panels were successfully used as the rMBR during the batch fermentations, which lasted for up to eight days without fouling. With the rMBR, complete glucose and xylose utilization, resulting in 86% of the theoretical ethanol yield, was observed with the synthetic medium. Its application with the pretreated wheat straw resulted in complete glucose consumption and 87% xylose utilization; a final ethanol concentration of 30.3 g/L was obtained, which corresponds to 83% of the theoretical yield. Moreover, complete in situ detoxification of furfural and HMF was obtained within 36 h and 60 h, respectively, with the rMBR. The use of the rMBR is a promising technology for large-scale lignocellulosic ethanol production, since it facilitates the co-utilization of glucose and xylose; moreover, the technology would also allow the reuse of the yeast for several batches.

Wheat straw pretreatment with KOH for enhancing biomethane production and fertilizer value in anaerobic digestion

Wheat straw biodegradability during anaerobic digestion was improved by treatment with potassium hydroxide (KOH) to decrease digestion time and enhance biomethane production and fertility value. KOH concentrations of 1% (K1), 3% (K2), 6% (K3) and 9% (K4) were tested for wheat straw pretreatment at ambient temperature with a C:N ratio of 25:1. 86% of total solids (TS), 89% of volatile solids (VS) and 22% of lignocellulose, cellulose and hemicellulose (LCH) (22%) were decomposed effectively with the wheat straw pretreated by 6% KOH. Enhanced biogas production and cumulative biomethane yield of 258ml·(gVS)−1 were obtained increased by 45% and 41% respectively, compared with untreated wheat straw. Pretreated wheat straw digestion also yielded a digestate with higher fertilizer values potassium (138%), calcium (22%) and magnesium (16%). These results show that TS, VS and LCH can be effectively removed from wheat straw pretreated with KOH, improving biodegradability biomethane production and fertilizer value.

Intensification of biogas production using pretreatment based on hydrodynamic cavitation

The present work investigates the application of hydrodynamic cavitation (HC) for the pretreatment of wheat straw with an objective of enhancing the biogas production. The hydrodynamic cavitation reactor is based on a stator and rotor assembly. The effect of three different speeds of rotor (2300, 2500, 2700rpm), wheat straw to water ratios (0.5%, 1% and 1.5% wt/wt) and also treatment times as 2, 4 and 6min have been investigated in the work using the design of experiments (DOE) approach. It was observed that the methane yield of 31.8ml was obtained with untreated wheat straw whereas 77.9ml was obtained with HC pre-treated wheat straw confirming the favourable changes during the pre-treatment. The combined pre-treatment using KOH and HC gave maximum yield of biogas as 172.3ml. Overall, it has been established that significant enhancement in the biogas production can be obtained due to the pretreatment using HC which can also be further intensified by combination with chemical treatment.

Enhanced saccharification for wheat straw with micro-thermal explosion technology of in situ SO3 reaction

In this paper, a novel pretreatment approach, named SO3 micro-thermal explosion, greatly improved the saccharification of wheat straw was conducted for the first time although this method has been effectively applied for the rice straw. After combing with dilute alkali, the pretreated wheat straw contained 59.9% cellulose, 19.3% hemicellulose and 8.7% lignin, which means 77.5% of lignin was removed while the cellulose and hemicellulose were slightly destroyed at the same time. At 60°C of the micro-thermal explosion temperature, the highest saccharification rate of the pretreated wheat straw was of 89.3% for 24h. By the SEM, XPS and FT-IR analysis, the major possible procedure of the SO3 micro-thermal explosion pretreatment process was proposed, among which the hydration of SO3 and esterification of lignin were the key reactions.

Cell wall disruption in low temperature NaOH/urea solution and its potential application in lignocellulose pretreatment

Pretreatments of wheat straw by NaOH/urea solvent at low temperature were investigated. To understand the cell wall disruption during this low temperature process, and its impacts on enzymatic hydrolysis, morphology, cellulose crystal structure, and chemical properties were investigated by using the following instruments: optical microscopy, confocal laser scanning microscopy, Fourier transform infrared spectra, and X-ray diffraction. The results implied that the deconstruction of plant cell wall at low temperature was attributed to disruption of the hydrogen bonds in cellulose and solubilization of hemicellulose and lignin. Meanwhile, the pretreatment approach resulted in almost full recovery of cellulose, approximately 60 % of lignin and 70 % of xylan removal, respectively. It’s interesting to note that cellulose I crystal structure in the substrate pretreated at a solid loading of 10 % was partially changed to cellulose II structure, while wheat straw pretreated at a higher solid loading of 20 %, retained the cellulose I structure. Almost complete saccharification (>95 %) of cellulose in pretreated substrates was achieved at a relatively low cellulase loading of 10 FPU/g substrates within 48 h. The loss of xylan in pretreated substrate had a negative effect on the total sugar recovery.

Ozone pretreatment of humid wheat straw for biofuel production

AbstractIn an attempt to maximize the amount of ozone reacting with lignin inside humid wheat straw, some of the ozone‐reactive lignin degradation products were washed away before a second ozonolysis delignification stage. The total contact time for the two stages was kept the same as that for a one‐stage process for comparison. A significant decrease in the Acid Insoluble Lignin (AIL) content of the straw resulted: from 13.04 wt. % (after a 30‐min one‐stage ozonolysis) to 9.34 wt. % (after a 30‐min two‐stage ozonolysis, separated by a washing step). This significant improvement was accompanied by an increase in released fermentable sugars from an enzymatic hydrolysis. The yield increased from 60% theoretical sugars to 80%. A further improvement in AIL (down to 7.36 wt. %) and released sugars (up to 90% theoretical) occurred when the moisture content (MC) of the straw entering the second stage was adjusted to the optimum value of the straw entering first stage (45 wt. %, predicted from an experimental design). The authors believe this is the first time results are published for the introduction of a two‐stage process separated by a washing step.

Comparison of the substrate enzymatic digestibility and lignin structure of wheat straw stems and leaves pretreated by green liquor

In this work, the substrate enzymatic digestibility (SED) and the lignin structure of green liquor (GL) pretreated wheat straw stems and leaves were investigated. Compared with wheat straw stems, leaves showed higher delignification selectivity in GL pretreatment and higher SED in enzymatic hydrolysis. Wet chemical analysis indicated that, characterized with lower content of syringyl units and less β-O-4 linkages, leaf lignin is structurally different from stem lignin. After GL pretreatment, the drops of both nitrobenzene oxidation and ozonation products yield of leaves were obviously higher than those of stems, which means that more β-O-4 linkages of leaf lignin were broken than that of stem lignin. The SED of total sugar in GL-pretreated leaves was about 50% higher than that in GL-pretreated stems. The less content and lower S/G ratio of lignin are suggested to be the important factors for the better SED of GL-pretreated leaves.

Continuous Ethanol Fermentation of Pretreated Lignocellulosic Biomasses, Waste Biomasses, Molasses and Syrup Using the Anaerobic, Thermophilic Bacterium Thermoanaerobacter italicus Pentocrobe 411

Lignocellosic ethanol production is now at a stage where commercial or semi-commercial plants are coming online and, provided cost effective production can be achieved, lignocellulosic ethanol will become an important part of the world bio economy. However, challenges are still to be overcome throughout the process and particularly for the fermentation of the complex sugar mixtures resulting from the hydrolysis of hemicellulose. Here we describe the continuous fermentation of glucose, xylose and arabinose from non-detoxified pretreated wheat straw, birch, corn cob, sugar cane bagasse, cardboard, mixed bio waste, oil palm empty fruit bunch and frond, sugar cane syrup and sugar cane molasses using the anaerobic, thermophilic bacterium Thermoanaerobacter Pentocrobe 411. All fermentations resulted in close to maximum theoretical ethanol yields of 0.47–0.49 g/g (based on glucose, xylose, and arabinose), volumetric ethanol productivities of 1.2–2.7 g/L/h and a total sugar conversion of 90–99% including glucose, xylose and arabinose. The results solidify the potential of Thermoanaerobacter strains as candidates for lignocellulose bioconversion.

Simultaneous saccharification and fermentation by co-cultures of Fusarium oxysporum and Saccharomyces cerevisiae enhances ethanol production from liquefied wheat straw at high solid content

A co-fermentation process involving Saccharomyces cerevisiae and Fusarium oxysporum was studied, using hydrothermally pretreated wheat straw as substrate. In the first step of the study, we examined liquefaction of the material in a free-fall reactor. Both the enzyme loading and the dry matter content affected severely the liquefaction efficiency. In the second step (simultaneous saccharification and fermentation (SSF) experiments), we found that the enzymatic system of F. oxysporum contributed significantly to substrate hydrolysis, while its metabolic system played a secondary role in fermentation. SSF in the presence of F. oxysporum cells and enzymes gave 62gL−1 ethanol. In the third step of the study, a semi-consolidated bioprocess was designed in which F. oxysporum culture (submerged or solid-state) was added at the SSF stage along with S. cerevisiae. The addition of solid F. oxysporum culture increased ethanol production by 19%, leading to a final ethanol concentration of 58gL−1. The present study proposes a semi-consolidated process combining two microorganisms for the fermentation at high solids concentration of a liquefied material using an in house free fall mixing reactor. The semi-consolidated process proposed not only increased the ethanol yields significantly, but could also lead to lower overall cost of the process by incorporating in-situ enzyme production.