Acid Pretreated Wheat Straw Research Articles

Polyhydroxyalkanoate Production Using Sulfuric Acid Pre-Treated Wheat Straw (SAPWS) as a Feedstock: RSM (Response Surface Methodology)-Based Optimization Using Bacillus paranthracis RSKS-3

Polyhydroxyalkanoate Production Using Sulfuric Acid Pre-Treated Wheat Straw (SAPWS) as a Feedstock: RSM (Response Surface Methodology)-Based Optimization Using Bacillus paranthracis RSKS-3

A reaction–diffusion coupled kinetic model for hydrothermal acid pretreatment of wheat straw

Hydrothermal acid pretreatment is a promising method to overcome the recalcitrance of lignocellulosic biomass for subsequent efficient enzymatic hydrolysis and biofuel production. However, little is known about heterogeneous catalysis reactions involving the proton diffusion in the pore of lignocellulosic biomass coupled with the hydrolysis of hemicellulose and cellulose catalyzed by proton. In this study, a reaction–diffusion coupled kinetic model for hydrothermal acid pretreatment of wheat straw was developed based on the visualization of particle geometry and pore features. The increase rate of average proton concentration in the pores is higher at a higher temperature or a smaller particle size. A mathematical model was successfully developed to describe the time courses of average proton concentration dictated by initial acid concentration and an unsteady diffusion fitting parameter. The kinetic parameters of each reaction step for hydrothermal acid pretreatment of wheat straw were obtained by fitting experimental data. The activation energies for the hydrolysis of slow-hydrolyzing cellulose, fast-hydrolyzing cellulose, and hemicellulose were determined of 937.8 kJ·mol−1, 90.7 kJ·mol−1, and 39.8 kJ·mol−1, respectively, indicating the temperature dependence of slow-hydrolyzing cellulose with a high crystalline index is strongest. The prediction accuracy of this model can be further improved at higher stirring speeds and initial acid concentrations. Additionally, the model demonstrates high prediction accuracy across three different particle sizes. Generally, this model can gratifyingly correlate data of formation and degradation of monosaccharides and furfural in the hydrothermal acid pretreatment of wheat straw with fair accuracy.

Efficient hemicellulose removal from lignocellulose by induced electric field-aided dilute acid pretreatment

This study evaluated the effectiveness of induced electric field (IEF) as a novel electrotechnology to assist dilute acid pretreatment of wheat straw (WS) at atmospheric pressure and low temperature (90 °C). The effects of acid concentration and duration on cellulose recovery, hemicellulose and lignin removal were investigated. Meanwhile, the differences between IEF pretreatment and hydrothermal pretreatment were compared by quantitative and qualitative analysis. The optimal pretreatment condition was acid concentration 1 % with the period of 5 h. Under the parameters, the hemicellulose removal of WS after IEF pretreatment was up to 73.6 %, and the enzymatic efficiency was 55.8 %. In addition, the irregular surface morphology, diminished functional groups associated with hemicellulose, increased specific surface area and pore volume, as well as improved thermal stability of the residual WS support the remarkable effect of IEF pretreatment. The feasibility of IEF pretreatment is might be due to the fact that the magneto-induced electric field promotes ionization of H+ and formation of hydrated hydrogen ions, increasing the acidity of the medium. Secondly, electroporation disrupts the anti-degradation structure of WS and increases the accessibility of cellulose to cellulases. It indicated that IEF is a green and efficient strategy for assisting the separation of hemicellulose from lignocellulose.

Insights on the acetic acid pretreatment of wheat straw: Changes induced in the biomass properties and benefits for the bio-oil production by pyrolysis

This work discloses how the pretreatment of wheat straw with acetic acid (AA) solutions modifies the biomass composition, strongly affecting the pyrolysis product distribution. AA in diluted solutions is a renewable and eco-friendly reagent, being also one of the main components of the pyrolysis bio-oil* (water-free basis). In comparison with water and diluted ammonia treatments, AA washing leads to a higher removal degree of alkali and alkaline-earth elements (AAEMs) from the biomass ash. In addition, the AA pretreatment reduces the content of char and gas precursors, as is the case of soluble lignin and extractives. Consequently, the bio-oil* yield is drastically increased up to ∼53 wt% during the pyrolysis of the AA washed wheat straw, being much higher than the value obtained for the raw biomass (∼35 wt%). Likewise, the bio-oil* composition is highly improved by the pretreatment with AA, dramatically increasing the concentration and yield of levoglucosan, which is a valuable precursor to produce both advanced biofuels and bio-based chemicals. In contrast, the opposite occurs during the pyrolysis of the extracted matter samples, recovered from the washing solutions, since its high content of AAEMs, lignin and extractives promotes the formation of char and gases in the detriment of the bio-oil fraction. Based on a preliminary techno-economic analysis, it is concluded that pretreatment with AA solutions may improve significantly the economic performance of the wheat straw pyrolysis process. This is due to the increased incomes coming from the higher yield of both bio-oil* and levoglucosan that largely compensate the additional capital and fresh AA costs.

Comparison of Saccharification And Lactic Acid Production Efficiencies From Chemically and Biologically Pretreated Wheat Straw

Background In recent times, agricultural waste has been utilized in many industries as an energy source in several processes. Wheat straw, one of the most cost-effective raw material, has a great potential to be utilized as a substrate in fermentation to produce lactic acid. Utilization of agro waste material as the carbon source provides a cheap and environment friendly production of lactic acid. Methods A comparison of chemical and biological pretreatment of wheat straw and the use of pretreated wheat straw hydrolysate in fermentation of Lactobacillus was carried out using optimized process parameters of temperature and ph. Pretreatment methods using dilute acid and white rot fungus Coriolis versicolor were performed on wheat straw as well as the effect of copretreatment with calcium hydroxide on differentially pretreated wheat straw was studied by analyzing sugar and lactic acid concentrations during fermentation. The effect of different pH (7, 8, and 9) on fermentation using dilute acid pretreated wheat straw was observed to lower the lactic production with the increase in ph. Dilute acid pretreatment of wheat straw provided the highest concentration of glucose at 57.2mg/L and subsequently enhanced yield of lactic acid during fermentation while the biologically pretreated wheat straw hydrolysate provided comparatively lower concentration of glucose at 49.2mg/L and thus decreased lactic acid production. Result The final lactic acid concentration of 48.14 mg/L was obtained in dilute acid pretreated wheat straw with Yp/s of 0.915 mg/mg, while the use of biologically pretreated wheat straw hydrolysate provided 39.56 mg/L concentration of lactic acid and an Yp/s of 0.908 mg/mg. However, a reduced lactic acid concentration of 27.03 mg/L and 20.62 mg/L was seen after the co-pretreatment of both dilute acid and fungal pretreated wheat straw with calcium hydroxide respectively, indicating its adverse effects on fermentation process. Conclusion Pretreatment of wheat straw with dilute acid can be considered a good saccharification method to obtain the optimum concentration of lactic acid in microbial fermentation carried out at optimum temperature and pH conditions.

Novel system design for high solid lignocellulosic biomass conversion

A novel system (Oregon State University High Solids Reactor; OSU-HSR) was designed and constructed for enzymatic hydrolysis at ultrahigh solids content (40%) by promoting better mixing using low energy consumption in a horizontal reactor with a new impeller design and a controllable feeding unit. System performance was evaluated using separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) methodologies. Using the dilute acid pretreated wheat straw as the substrate in the OSU-HSR system, the highest glucose (219.7 g/L) and ethanol (127.1 g/L) concentrations were achieved with the use of the SHF method while the highest ethanol concentration using SSF method was 134.5 g/L. The SSF method increased the return on investment to 12.21% with an estimated global warming potential of 54.5 g CO2 eq/MJ Ethanol. The OSU-HSR successfully provided effective mixing and different fed-batch schemes, and can be used for efficient biochemical conversion of lignocellulosic biomass into bio-chemicals and biofuels.

Understanding the toxicity of lignin-derived phenolics towards enzymatic saccharification of lignocellulose for rationally developing effective in-situ mitigation strategies to maximize sugar production from lignocellulosic biorefinery

The lignin-derived phenolics are highly inhibitory toward lignocellulose enzymatic hydrolysis, while the relationship between phenolic structure and inhibitory effect is still not fully understood. In this study, the compositions of phenolics from dilute acid pretreated wheat straw were analyzed and their impact on cellulose hydrolysis was studied. With increase of pretreatment severity, more toxic phenolics were produced from lignin degradation reactions, which were the major contributor to the increased inhibitory effect of pretreatment hydrolysate towards cellulases. Through analyzing the relationship of phenolic structure and their inhibitory effect, a useful model was developed to predict the phenolics-caused inhibition by combining the indexes of electrophilicity and hydrophobicity. Further, through understanding the interactions between phenolics and cellulases, a novel biocomponent alleviator was rationally designed to block the phenolics-cellulase interactions, the degree of improvement of enzymatic hydrolysis reached as high as 135.8%. This study provides directions for developing more effective pretreatment and detoxification methods.

Model development for the optimization of operational conditions of the pretreatment of wheat straw

• Biomass pretreatment experiments and model development for process design purposes. • Hydrothermal pretreatment of wheat straw not competitive. • Dilute acid pretreatment of wheat straw has monomer yields of. Y = 98 % w / w . • Machine learning and mechanistic models have good validation metrics. • The latter performs best in optimization of operation conditions under uncertainty. The underlying study presents models for the optimization of operational conditions of lignocellulosic biomass pretreatment to facilitate the conceptual process design of biorefineries. Experiments for hydrothermal and dilute acid pretreatment are performed and analyzed. The highest xylose monomer yield obtained for dilute acid pretreatment is Y Xyl = 98 % at a temperature of T = 195 °C , a reaction time of t = 18 m i n and a dilute acid concentration of C acid = 1.25 w t % . The data is used to fit a response surface model (RSM), a Gaussian process regression model (GPR), and a mechanistic model based on thermodynamic principles and first-order rate equations. All models are validated respectively with a coefficient of determination of R RSM 2 = 0.914 , R GPR 2 = 0.999 and R mech 2 = 0.988 . Each model is used in an optimization problem to predict the optimal operational conditions that maximize the xylose yield. The conditions found by the mechanistic model T = 191 . 6 ° C , t = 18 m i n , C ac = 1.13 w t % with C Xyl , m e c h = 23.47 w t % and the GPR T = 195 ° C , t = 18 m i n , C ac = 1.25 w t % with C Xyl , G P R = 23.23 w t % are in agreement and stand out compared to the RSM metamodeling approach T = 182 . 4 ° C , t = 26.2 m i n , C ac = 1.25 w t % , which yields C Xyl , R S M = 25.72 w t % . Considering the scenario of uncertainty in the feedstock composition, the optimization under this uncertainty with the mechanistic model yields slightly different conditions T = 182 . 6 ° C , t = 18 m i n , C ac = 0.84 w t % and C Xyl , m e c h , u c = 20.88 w t % . Given the underlying phenomena in the biomass pretreatment, all models have shortcomings; however, the mechanistic model is validated best overall and is thus recommended for further engineering purposes as, e.g., the conceptual process design of biorefineries.

An integrated biorefinery process for co-production of xylose and glucose using maleic acid as efficient catalyst

This study aims to valorize wheat straw for xylose and glucose recovery using maleic acid in the pretreatment. The process conditions of maleic acid hydrolysis of wheat straw for xylose recovery were optimized by response surface methodology, through which the maximum xylose recovery of 77.12% versus minimum furfural yield of 1.61% were achieved using 70 g/L solid-to-liquid ratio and 0.1 mol/L maleic acid for 40 min at 150 °C. Moreover, 88.58% cellulose conversion was achieved by enzymatic hydrolysis of maleic acid-pretreated wheat straw. Results showed that maleic acid was an effective pretreatment solvent for sugars recovery: 19.88 g xylose and 30.89 g glucose were respectively obtained from 100 g wheat straw due to acidic and enzymatic hydrolysis, with only 0.37 g furfural produced. This study provides a strategy for hydrolyzing wheat straw to produce fermentable sugars with low amount of degradation product.

Synergistic Action of a Lytic Polysaccharide Monooxygenase and a Cellobiohydrolase from Penicillium funiculosum in Cellulose Saccharification under High-Level Substrate Loading.

Lytic polysaccharide monooxygenases (LPMOs) are crucial industrial enzymes required in the biorefinery industry as well as in the natural carbon cycle. These enzymes, known to catalyze the oxidative cleavage of glycosidic bonds, are produced by numerous bacterial and fungal species to assist in the degradation of cellulosic biomass. In this study, we annotated and performed structural analysis of an uncharacterized LPMO from Penicillium funiculosum (PfLPMO9) based on computational methods in an attempt to understand the behavior of this enzyme in biomass degradation. PfLPMO9 exhibited 75% and 36% sequence identities with LPMOs from Thermoascus aurantiacus (TaLPMO9A) and Lentinus similis (LsLPMO9A), respectively. Furthermore, multiple fungal genetic manipulation tools were employed to simultaneously overexpress LPMO and cellobiohydrolase I (CBH1) in a catabolite-derepressed strain of Penicillium funiculosum, PfMig188 (an engineered variant of P. funiculosum), to improve its saccharification performance toward acid-pretreated wheat straw (PWS) at 20% substrate loading. The resulting transformants showed improved LPMO and CBH1 expression at both the transcriptional and translational levels, with ∼200% and ∼66% increases in ascorbate-induced LPMO and Avicelase activities, respectively. While the secretome of PfMig88 overexpressing LPMO or CBH1 increased the saccharification of PWS by 6% or 13%, respectively, over the secretome of PfMig188 at the same protein concentration, the simultaneous overexpression of these two genes led to a 20% increase in saccharification efficiency over that observed with PfMig188, which accounted for 82% saccharification of PWS under 20% substrate loading.IMPORTANCE The enzymatic hydrolysis of cellulosic biomass by cellulases continues to be a significant bottleneck in the development of second-generation biobased industries. While increasing efforts are being made to obtain indigenous cellulases for biomass hydrolysis, the high production cost of this enzyme remains a crucial challenge affecting its wide availability for the efficient utilization of cellulosic materials. This is because it is challenging to obtain an enzymatic cocktail with balanced activity from a single host. This report describes the annotation and structural analysis of an uncharacterized lytic polysaccharide monooxygenase (LPMO) gene in Penicillium funiculosum and its impact on biomass deconstruction upon overexpression in a catabolite-derepressed strain of P. funiculosum Cellobiohydrolase I (CBH1), which is the most important enzyme produced by many cellulolytic fungi for the saccharification of crystalline cellulose, was further overexpressed simultaneously with LPMO. The resulting secretome was analyzed for enhanced LPMO and exocellulase activities and the corresponding improvement in saccharification performance (by ∼20%) under high-level substrate loading using a minimal amount of protein.

Effect of ascorbic acid assisted dilute acid pretreatment on lignin removal and enzyme digestibility of agricultural residues

Efficient pretreatment for lignocellulosic biomass is crucial in developing a viable biorefinery process. An ascorbic acid (AsA)-assisted dilute acid pretreatment strategy was developed to improve enzymatic hydrolysis efficiency. In this study, the effect of ascorbic acid addition on the dilute acid pretreatment of wheat straw (WS), corn stover (CS), and corncob (CC) was assessed and compared. The 72 h hydrolysis yield was improved by 12.47, 18.78, and 13.57% in dilute acid pretreated WS, CS, and CC with ascorbic acid addition, respectively. In addition, the cellulose accessibility, enzyme adsorption, chemical composition analysis, and structural features of pretreated biomass with ascorbic acid were determined to better understand its mechanistic effect on enzymatic hydrolysis. The results indicated that the addition of ascorbic acid in the dilute acid pretreatment reduced surface lignin content and enhanced cellulose accessibility, delignification ratio, and enzyme adsorption ability.

One-pot process for lactic acid production from wheat straw by an adapted Bacillus coagulans and identification of genes related to hydrolysate-tolerance

In this study, Bacillus coagulans CC17A with highly tolerant to hydrolysate was obtained through adaptive evolution. After 63 generations, the strain CC17A was stably in 45% (v/v) hydrolysate media and could digest multiple inhibitors in the hydrolysate. Based on its promising features, a one-pot process was developed to produce lactic acid (LA) from wheat straw. After dilute acid pretreatment of wheat straw, simultaneous saccharification and co-fermentation was conducted using CC17A without any solid-liquid separation and pre-detoxification. Total 35.50 g LA was produced from 80 g raw substrate and the production yield was as high as 70.9% of theoretical. To elucidate the tolerance mechanism, transcriptomic profiling of CC17A was studied. The highly up-regulated oxidoreductases and phenolic acid decarboxylase are considered to be involved with the inhibitors-tolerance of B. coagulans CC17A.

Comparisons of catalytic efficiency during the reduction of lignocellulosic substrates between free enzyme versus enzyme bound to mobile enzyme sequestration platforms (mESP)

Plants represent a vast, renewable source of biomass. Plant biomass serves as a major substrate for sustainable biofuel production. However, to overcome the food‐versus‐fuel dilemma, effective use of plant residues for cellulosic (versus corn‐ or sugarcane‐based) ethanol must be realized. Effective deconstruction of lignocellulosic matrix and efficiently accessing and reducing cellulose to fermentable sugars (i.e., glucose) would overcome current constraints that prevent cellulosic ethanol from becoming an economically viable alternative for liquid/transportation fuel. Cellulosic feedstocks consist of cellulose (20–50%), hemicellulose (15–35%), and lignin (5–30%). In previous work, we demonstrated that the use of thermotolerant and acidotolerant engineered mobile enzyme sequestration platforms (mESP) could enhance lignocellulosic deconstruction of two acid pretreated (and alkaline pretreated) feedstocks. Specifically, acid‐pretreated wheat straw and corn pericarp were subjected to a suite of cellulases, an enzyme cocktail, under two conditions: (a) pretreated substrate plus enzymes free in solution (experimental control); and, (b) pretreated substrate plus enzymes bound to a prototype mESP. The mESP‐bound enzymes showed enhanced ability to convert complex carbohydrates to glucose (i.e., sugar reduction) when compared to the free enzyme in solution control (at equimolar enzyme concentrations). Although the mESP was known to be thermotolerant and acidotolerant, enhancement of sugar reduction efficiency was also observed with alkaline pretreated substrate. Still, these preliminary experiments only demonstrated a 2‐ to 3‐fold increase in enzymatic efficiency over controls. Indeed, with some enzyme ‘cocktails’, sugar reduction efficiency actually decreased when employing mESPs. It was suggested that steric interference between enzymes due to the close proximity of enzyme attachment points on the platform and the use of enzymes with different target points (exo‐versus endo‐) on the substrate (i.e., cellulose) may limit the magnitude of enhancement that can be achieved. After re‐engineering the mESP system to separate attachment points and strategic development of free enzyme cocktails and enzyme composition on charged mESPs, this study demonstrates that next‐generation mESPs can improve catalytic efficiency more than 3‐fold. In addition, alternative substrates have been tested (e.g., rice straw) with similar results. These results and implications for mESP technology are discussed in detail.Support or Funding InformationU.S. National Science Foundation Molecular and Cellular Biosciences (MCB) grant (Award No. 1818346; PI‐Ceballos); U.S. National Science Foundation Research Coordination Network (RCN) grant (Award No. 1624171; PI‐Ceballos)

Bioconversion of pretreated wheat straw to ethanol by Monascus purpureus CBS 109.07 and Fusarium venenatum ATCC 20334 using simultaneous saccharification and fermentation

Abstract. Yudianto D, Nainggolan EA, Millati R, Hidayat C, Lennartsson P, Taherzadeh MJ, Niklasson C. 2019. Bioconversion of pretreated wheat straw to ethanol by Monascus purpureus CBS 109.07 and Fusarium venenatum ATCC 20334 using simultaneous saccharification and fermentation. 20: 2229-2235. Fractions of sulfuric acid-pretreated wheat straw, i.e. solid, liquid, and a mixture of liquid and solid were used as substrates in simultaneous saccharification and fermentation (SSF) process to produce ethanol. The bioconversion was performed by Monascus purpureus CBS 109.07 and Fusarium venenatum ATCC 20334. The highest ethanol yields from solid, liquid and a mixture of solid and liquid fractions by M. purpureus CBS 109.07 were 0.36, 0.41, and 0.37 g/g glucose, respectively. The corresponding values by F. venenatum ATCC 20334 were 0.21, 0.54, 0.35 g/g glucose, respectively.

Dry biodetoxification of acid pretreated wheat straw for cellulosic ethanol fermentation

BackgroundThe efficient removal of toxic inhibitors from pretreated lignocellulose biomass is crucially important for consequent cellulosic ethanol fermentation. A. resinae ZN1 biodetoxifies all toxic inhibitors at the neutral pH of 4–6, and the neutralization of acid catalyst in the pretreated lignocellulose is required. However, aqueous alkaline solutions such as sodium hydroxide solution and calcium hydroxide slurry are used which generate several difficulties.ResultsIn this study, a dry biodetoxification method was investigated using dry calcium carbonate (CaCO3) powder as an acid-neutralizing reagent to avoid the use of an aqueous alkaline solution. Dry biodetoxification provides a mild and stable pH without the generation of phenolic compounds. The acid pretreated and dry biodetoxified wheat straw was used as the feedstock of ethanol fermentation and the same performance with the wet biodetoxification using aqueous Ca(OH)2 slurry. The 72 g/L or 9.1% (v/v) of ethanol produced from wheat straw was very close to that of ethanol from corn starch.ConclusionsDry biodetoxification provided a practical method to simplify the process of conventional wet biodetoxification to reduce the time, cost and labor.

Bioethanol Production from Dilute-acid Pre-treated Wheat Straw Liquor Hydrolysate by Genetically Engineered Saccharomyces cerevisiae

Sustainable recycling of lignocellulosic biomass includes utilization of all carbohydrates present in its hydrolysates. Since wheat straw is a xylose-rich raw material, utilization of xylose from obtained liquid part (liquor) of hydrolysates improves overall bioprocess efficiency. In this work, dilute acid pre-treatment of wheat straw was performed in high-pressure reactor at different temperatures (160 °C – 200 °C), residence times (1 min – 10 min), and acids (H2SO4 and H3PO4) concentrations. During dilute acid pre- treatment, hemicellulose is degraded to pentose sugars that cannot be used by industrial ethanol- producing yeasts. Therefore, genetically engineered Saccharomyces cerevisiae strain that can utilize xylose was used. Fermentations were performed on different xylose-rich liquor wheat straw hydrolysates in shake-flasks and in horizontal rotating tubular bioreactor. The efficiency of fermentations carried out in shake flasks using xylose- rich liquor wheat straw hydrolysates were in the range of 19.61 – 74.51 %. However, the maximum bioprocess efficiency (88.24 %) was observed during fermentation in the HRTB on the liquor wheat straw hydrolysate obtained by pre- treatment with 2 % w/w phosphoric acid.

Phenomenological modeling and evaluation of formic acid pretreatment of wheat straw with an extended combined severity factor for biomass fractionation and enzymatic saccharification to produce bioethanol

Abstract Chemical pretreatment of lignocellulosic biomass is a complex system involving heterogeneity and complicated reactions. Rigorous kinetic modeling of this complex system is not possible, but phenomenological modeling with parameter of severity factor (SF) may provide useful information in a wide operational range. In the present work, an extended combined severity factor ( CSF ext ) was defined by involving the contribution of solvent concentration for modeling and evaluating formic acid pretreatment of wheat straw in order to achieve a fractionation of the biomass components and improve cellulose digestibility for bioethanol production. Two phenomenological models based on classical Arrhenius and modified Logistic equations were developed to describe the solubilization of the biomass polymeric components. Although the determined values of CSF ext were somewhat different based on Arrhenius and Logistic models, the tendency of the component solubilization with respect to CSF ext was similar. With integrated consideration of biomass components solubilization, formylation of cellulose and enzymatic glucan conversion, the pretreatment condition was suggested be controlled at Arrhenius-based CSF ext of 23–24 or Logistic-based CSF ext of 25–26. CSF ext thus can be applied as an integrated parameter involving the contribution of temperature, time and solvent concentration to the reaction severity for evaluating the pretreatment process.

The promotional effect of water-soluble extractives on the enzymatic cellulose hydrolysis of pretreated wheat straw

Enzymatic cellulose hydrolysis of pretreated wheat straw pulp to glucose is enhanced when the hydrolysis is performed in the presence of an aqueous extract of the wheat straw. A relative digestibility increase of about 10% has been observed for organosolv, alkaline and dilute acid pretreated wheat straw pulp (enzyme dose 2.5FPU/g pulp). At lower enzyme doses, the extract effect increases leading to an enzyme dose reduction of 40% to obtain a glucose yield of 75% within 48h using organosolv wheat straw pulp. Possibly, cellulase deactivation by irreversible binding to pulp lignin is reduced by competition with proteins in the extract. However, since the extract effect has also been demonstrated for lignin-lean substrates, other effects like improved accessibility of the pulp cellulose (amorphogenesis) cannot be excluded. Overall, this contribution demonstrates the positive effect of biomass extractives on enzymatic cellulose digestibility, thereby reducing costs for 2G biofuels and bio-based chemicals.

Integrated Process for Ethanol, Biogas, and Edible Filamentous Fungi-Based Animal Feed Production from Dilute Phosphoric Acid-Pretreated Wheat Straw

Integration of wheat straw for a biorefinery-based energy generation process by producing ethanol and biogas together with the production of high-protein fungal biomass (suitable for feed application) was the main focus of the present study. An edible ascomycete fungal strain Neurospora intermedia was used for the ethanol fermentation and subsequent biomass production from dilute phosphoric acid (0.7 to 1.2% w/v) pretreated wheat straw. At optimum pretreatment conditions, an ethanol yield of 84 to 90% of the theoretical maximum, based on glucan content of substrate straw, was observed from fungal fermentation post the enzymatic hydrolysis process. The biogas production from the pretreated straw slurry showed an improved methane yield potential up to 162% increase, as compared to that of the untreated straw. Additional biogas production, using the syrup, a waste stream obtained post the ethanol fermentation, resulted in a combined total energy output of 15.8 MJ/kg wheat straw. Moreover, using thin stillage (a waste stream from the first-generation wheat-based ethanol process) as a co-substrate to the biogas process resulted in an additional increase by about 14 to 27% in the total energy output as compared to using only wheat straw-based substrates.Graphical

Cultivation of Podospora anserina on soybean hulls results in an efficient enzyme cocktail for plant biomass hydrolysis

The coprophilic ascomycete fungus Podospora anserina was cultivated on three different plant biomasses, i.e. cotton seed hulls (CSH), soybean hulls (SBH) and acid-pretreated wheat straw (WS) for four days, and the potential of the produced enzyme mixtures was compared in the enzymatic saccharification of the corresponding lignocellulose feedstocks. The enzyme cocktail P. anserina produced after three days of growth on SBH showed superior capacity to release reducing sugars from all tested plant biomass feedstocks compared to the enzyme mixtures from CSH and WS cultures. Detailed proteomics analysis of the culture supernatants revealed that SBH contained the most diverse set of enzymes targeted on plant cell wall polymers and was particularly abundant in xylan, mannan and pectin acting enzymes. The importance of lytic polysaccharide monooxygenases (LPMOs) in plant biomass deconstruction was supported by identification of 20 out of 33 AA9 LPMOs in the SBH cultures. The results highlight the suitability of P. anserina as a source of plant cell wall degrading enzymes for biotechnological applications and the importance of selecting the most optimal substrate for the production of enzyme mixtures.