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Lignin is the most abundant source of renewable aromatics on Earth, yet its enormous potential remains underexploited in current biorefinery and pulping processes. The extensive degree of condensation of the lignin fractions produced via the most widely adopted biomass pretreatments (i.e. “technical lignin”) poses a prominent limitation to their subsequent conversion toward valuable products. In this work, a broad range of methods for biomass pretreatment are reviewed, illustrating the impact of each strategy on the properties of the isolated lignin and carbohydrate fractions. The main pathways for the valorization of the obtained lignin streams (i.e. toward polymeric materials or chemicals) are critically discussed, and the relationship existing between (i) native lignin structure, (ii) pretreatment conditions, and (iii) lignin processability is rationalized. A key aspect for producing lignin streams amenable to further upgrading is the prevention of condensation reactions between lignin fragments during biomass fractionation. In this respect, a class of so-called “lignin-first” pretreatments, targeting the prompt stabilization of reactive lignin intermediates to minimize lignin condensation, has recently gained momentum. Herein, lignin-first approaches are reviewed, discussing in detail the fate of lignin, cellulose, and hemicellulose for each strategy. The potential of lignin-first biorefineries to realize a more complete valorization of lignocellulose and the current limitations of each method are highlighted. Overall, this work provides a comprehensive overview of the technologies that are available or currently emerging for lignin isolation and subsequent valorization., SCOPUS: re.j, info:eu-repo/semantics/published

The development of biomass pretreatment approaches that, next to (hemi)cellulose valorization, aim at the conversion of lignin to chemicals is essential for the long-term success of a biorefinery. Herein, we discuss a dithionite-assisted organosolv fractionation (DAOF) of lignocellulose in n-butanol and water to produce cellulosic pulp and mono-/oligo-aromatics. The present study frames the technicalities of this biorefinery process and relates them to the features of the obtained product streams. Via the extensive characterization of the solid pulp (by acid hydrolysis-HPLC, ATR-FTIR, XRD, SEM and enzymatic hydrolysis-HPLC), of lignin derivatives (by GPC, GC-MS/FID, 1H-13C HSQC NMR, and ICP-AES) and of carbohydrate derivatives (by HPLC) we comprehensively identify and quantify the different products of interest. These results were used for inspecting the economic feasibility of DAOF. The adoption of a dithionite loading of 16.7% w/wbiomass and of an equivolumetric mixture of n-butanol and water, which led to a high yield of monophenolics (~20%, based on acid insoluble lignin, for the treatment of birch sawdust), was identified as the most profitable process configuration. Furthermore, the treatment of various lignocellulosic feedstocks was explored, which showed that DAOF is particularly effective for processing hardwood and herbaceous biomass. Overall, this study provides a comprehensive view of the development of an effective dithionite-assisted organosolv fractionation method for the sustainable upgrading of lignocellulosic biomass.

Lignin is the most abundant source of renewable aromatics on Earth, but its tendency to undergo irreversible condensation reactions during lignocellulose pretreatment hampers its valorization in current biorefinery schemes. A strategy for circumventing this issue is the so-called reductive catalytic fractionation (RCF), which relies on the use of redox catalysts and hydrogen gas to promote the reductive cleavage of lignin and to prevent lignin condensation, ultimately yielding low-molecular weight phenolics, along with a delignified (hemi)cellulose fraction. Some limitations must be overcome to improve the potential of RCF. The treatment of biomass feedstocks alternative to the widely explored virgin wood is important for extending the range of applications of this method. In addition, the recurrent adoption of high pressures of hydrogen gas poses safety and equipment constraints. This dissertation reports on research undertaken to investigate the RCF of wheat straw, an inexpensive and abundantly available agricultural residue, with a focus on the study of hydrogen-free process configurations. Moreover, an innovative dithionite-assisted organosolv fractionation (DAOF) method for the reductive depolymerization of lignin within biomass pretreatment is developed, based on the use of sodium dithionite as a reducing agent, instead of hydrogen gas and redox catalysts. Overall, this dissertation shows that RCF and DAOF represent promising approaches for the sustainable production of light aromatics via the reductive depolymerization of lignin., (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2022

The development of biomass pretreatment approaches that, next to (hemi)cellulose valorization, aim at the conversion of lignin to chemicals is essential for the long-term success of a biorefinery. Herein, we discuss a dithionite-assisted organosolv fractionation (DAOF) of lignocellulose in n-butanol and water to produce cellulosic pulp and mono-/oligo-aromatics. The study frames the technicalities of this biorefinery process and relates them to the features of the obtained product streams. We comprehensively identify and quantify all products of interest: solid pulp (acid hydrolysis-HPLC, ATR-FTIR, XRD, SEM, enzymatic hydrolysis-HPLC), lignin derivatives (GPC, GC–MS/FID, 1H–13C HSQC NMR, ICP-AES), and carbohydrate derivatives (HPLC). These results were used for inspecting the economic feasibility of DAOF. In the best process configuration, a high yield of monophenolics was reached (∼20 wt%, based on acid insoluble lignin in birch sawdust). Various other lignocellulosic feedstocks were also explored, showing that DAOF is particularly effective on hardwood and herbaceous biomass. Overall, this study demonstrates that DAOF is a viable fractionation method for the sustainable upgrading of lignocellulosic biomass.

The reductive catalytic fractionation (RCF) is a promising method for the development of “lignin-first” biorefineries. Apart from the widely investigated virgin woody biomass, it is essential to explore the potential of waste biomass feedstocks. Herein, the RCF of wheat straw is examined to produce lignin mono-/oligomers along with a processable carbohydrate pulp. The use of different catalysts (Ru/C and Ru/Al2O3) and catalyst loadings (0–20% w/wbiomass) revealed the superior performance of Ru/C, which resulted in the largest yield of phenolic monomers (up to ∼25 wt % of initial acid-insoluble lignin) and in the lowest formation of high-molecular-weight fragments in the extracted lignin oil. Furthermore, the operating temperature was shown to substantially affect both lignin extraction–depolymerization and polysaccharides preservation–processability. For a reaction time of 3 h, an increase of the temperature from 200 to 250 °C resulted in a >2-fold boost of the yields of lignin oil and monophenolics, while the recovery of polysaccharides decreased by about 30 wt % (with ∼20% lower enzymatic digestibility). An economic assessment highlighted that the high-temperature treatment becomes the most profitable configuration as the market price of lignin products increases. Overall, this work provides insight into the adoption of the RCF for the upgrading of lignocellulose from inexpensive and widely available wheat straw biomass.

The stone of L. remains the least known morphological part of this plant, whereas the fruit is appreciated for both consumption purposes and biological activity. The stone is considered to be a byproduct of fruit processing and very little is known about its phytochemical composition and biological properties. In this study, the complete qualitative determination of hydrolyzable tannins, their quantitative analysis, total polyphenolic content, and antioxidant properties of the stone of are presented for the first time. The 37 identified compounds included the following: various gallotannins (), monomeric ellagitannins (), dimeric ellagitannins (), and trimeric ellagitannins (). The presence of free gallic acid and ellagic acid was also reported. Our results demonstrate that stone is a source of various bioactive hydrolyzable tannins and shows high antioxidant activity which could allow potential utilization of this raw material for recovery of valuable pharmaceutical or nutraceutical substances. The principal novelty of our findings is that hydrolyzable tannins, unlike other polyphenols, have been earlier omitted in the evaluation of the biological activities of . Additionally, the potential recovery of these bioactive chemicals from the byproduct is in line with the ideas of green chemistry and sustainable production.

Residual banana bulbs (RBB) were characterized and assessed as a potential starch and cellulose-based feedstock for bioethanol production. To facilitate the enzymatic digestibility, hydrothermal pretreatment was performed on RBB prior to simultaneous saccharification and fermentation (SSF) with Saccharomyces cerevisiae. Composition of RBB was similar to traditional starch and cellulose-based feedstocks with high glucan (60 g/100 gDM) and relatively low lignin content (7 g/100 gDM). Both amylase and cellulase were needed to efficiently hydrolyze RBB. The highest ethanol yield (310 kg EtOH/ton_DM_RBB, 93% of theoretical production based on total available glucose) was obtained with non-pretreated RBB. SSF can be carried out at lower RBB concentrations. Hydrothermal pretreatment affected negatively the bioethanol potential due to the loss of fermentable carbohydrates. In a case study of an African leading producer of bananas and plantains (Cameroon), the energy derived from bioethanol was 80 GWh ethanol/year and corresponded to 1.6% of the annual transportation requirement. This study shows that RBB is a promising alternative feedstock for bioethanol production.

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Les micropolluants sont des composés ayant un impact négatif sur les organismes de l’environnement et ce, même lorsqu’ils sont présents à de très faibles concentrations (ng L−1 au µg L−1). Une vaste gamme d’impacts est liée à la présence des micropolluants, notamment des problèmes de toxicité à long et court termes, des problèmes de perturbation endocrinienne et le développement d’antibiorésistance.Comme les stations d’épuration (STEPs) actuelles n’ont pas été conçues pour éliminer les micropolluants, elles constituent une importante source de relargage de micropolluants dans l’environnement. Un moyen alternatif de traiter les micropolluants serait l’utilisation de laccases. Les laccases sont des enzymes produites principallement par les champignons de la pourriture blanche du bois et qui sont capables de catalyser l’oxydation d’un substrat avec la réduction simultanée d’oxygène en eau. Le substrat oxydé forme un radical réactif qui peut alors intervenir dans des réactions non-enzymatiques comme la réticulation de monomères, la dégradation de polymères ou le clivage de cycles aromatiques. Les laccases sont capables d’oxyder, de polymériser ou de transformer des composés phénoliques ou anthropogéniques en des dérivés moins toxiques.Dans les milieux aquatiques réels, comme les effluents de STEPs, les micropolluants sont présents sous forme de mélanges. La présence de ces mélanges peut mener à des problèmes d’écotoxicité plus importants que ceux observés dans avec des solutions ne contenant qu’un seul micropolluant. Par exemple, il a été montré qu’un mélange de différents anti-inflammatoires non-stéroïdiens (diclofénac, ibuprofène, naproxène et acide acétylsalicylique) était considérablement toxique pour le crustacé planctonique Daphnia et l’algue verte planctonique Scenedesmus subspicatus même à des concentrations auxquelles ces anti-inflammatoires seuls ne provoquaient que très peu ou pas d’effets. La présence de micropolluants sous forme de mélanges dans les milieux, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

In this study Salicornia sinus-persica, a succulent halophyte was assessed for its potential to be used as a feedstock for bioethanol production. For such succulent, salty, green biomasses, direct fractionation and fermentation allow for water preservation in the process. Fresh biomass of S. sinus-persica was collected and split into two fractions by wet fractionation; liquid (juice) and solid (pulp). Sugar contents were found to be 1.0–1.5% for the juice fraction and 50% (w/w) for the fresh pulp. Direct fermentation of the juice using Saccharomyces cerevisiae showed no salt inhibition of the yeast and ethanol yields of ~70% were achieved. A pretreatment study was carried out for the pulp fraction applying mild hydrothermal pretreatment. Cellulose convertibility was found to be significantly higher for severity factors above 2.00, and the highest ethanol yield (76.91 ± 3.03%) was found at process severity of 3.06 (170 °C, 10 min)

Date palm residues are one of the most promising lignocellulosic biomass for bioethanol production in the Middle East. In this study, leaflets and rachis were subjected to hydrothermal pretreatment to overcome the recalcitrance of the biomass for enzymatic conversion. Evident morphological, structural, and chemical changes were observed by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy after pretreatment. High glucan (>90% for both leaflets and rachis) and xylan (>75% for leaflets and >79% for rachis) recovery were achieved. Under the optimal condition of hydrothermal pretreatment (210°C/10 min) highly digestible (glucan convertibility, 100% to leaflets, 78% to rachis) and fermentable (ethanol yield, 96% to leaflets, 80% to rachis) solid fractions were obtained. Fermentability test of the liquid fractions proved that no considerable inhibitors to Saccharomyces cerevisiae were produced in hydrothermal pretreatment. Given the high sugar recovery, enzymatic digestibility, and ethanol yield, production of bioethanol by hydrothermal pretreatment could be a promising way of valorization of date palm residues in this region.

alm tree trimmings represent primary landscaping residue in the United Arab Emirates, making it an easily accessible feedstock for bio-based products generation. This study examines organosolv treatment of the palm fronds as a method of delignification and fractionation of this lignocellulosic biomass. The results revealed that treating palm fronds with ethanol-water mixture at elevated temperature (200oC) results in up to 43% lignin recovery with no catalyst added. This corresponds to production of 13 g lignin per 100 g raw dry biomass. Over 90% glucan was found to be retained in the solid fiber fraction after the treatment, producing cellulose-rich pulp. Previous article in issue

Seagrass (Halodule uninervis) native to Abu Dhabi was sampled in various locations thorough February to June 2013. Chemical composition was analyzed, which included ash, extractives, structural carbohydrates, acid insoluble residue and CHNSO content. The theoretical methane yield was calculated based on the CHN content using Buswell's formula. Anaerobic digestion was performed with the use of sewage sludge. Three concentrations of seagrass biomass were tested (1%, 3%, 5% of VS) to evaluate the practical methane yield. The highest specific methane yield was obtained for 1% loading rate and resulted in 122 ml/gVS, which corresponds to 30% of theoretical methane yield.

Salicornia bigelovii straw was characterized and evaluated as a potential lignocellulosic bioethanol feedstock. S. bigelovii used in the study was grown in the United Arab Emirates using saltwater (40 ppt) for irrigation. Salt removal was performed prior to pretreatment to protect the processing equipment and avoid inhibition of enzymes and yeast. Composition of the washed biomass was comparable to traditional lignocellulosic biomasses with relatively high glucan and xylan content (26 and 22 g/100 gDM, respectively) but with lower lignin content (7 g/100 gDM). The washed feedstock was subjected to hydrothermal pretreatment, producing highly digestible (up to 92% glucan-to-glucose conversion) and fermentable (up to 100% glucose-to-ethanol conversion) fiber fractions. Liquid fractions obtained in the pretreatment did not show inhibition towards Saccharomyces cerevisiae. No significant differences among the enzymatic convertibility and microbial fermentability of the fibers as well as low xylose recoveries suggest that lower severity pretreatment conditions could be exploited for S. bigelovii. Previous article in issue

We discuss the potential of using halophytes as a source for producing liquid biofuels. We review the potential pathways for converting oilseeds into biodiesel and bio-derived synthetic paraffinic kerosene and presents some preliminary data on biomass composition and pretreatment of the halophyte Salicornia bigelovii. Six samples of S. bigelovii cultivated at three fertilizer levels (F1: 1 gN/m2, F2: 1.5 gN/m2 and F3: 2 gN/m2) and two salinity levels (S1: 10 ppt and S5: 50 ppt salt) were analyzed with regard to chemical composition and bioethanol potential. Chemical characterization showed that S. bigelovii contained, 16.31–55.67 g/100gTS (total solids) of carbohydrates, 5.42–16.60 g/100gTS of lignin, 27.85–66.37 g/100gTS of total extractives (including extractable ash), and 2.18–9.68 g/100gTS of structural ash, depending on the plant fraction and cultivation conditions. Enzymatic hydrolysis of the pretreated samples revealed high glucose recoveries of up to 90 % (of glucose in raw S. bigelovii) corresponding to ethanol yield of 111 kg ethanol/dry ton S. bigelovii.

Ethanol production from low severity pretreated (85 °C, 1 h) solid household waste was studied using simultaneous saccharification and fermentation (SSF). The aim of the study was to examine typical composition of the organic fraction of municipal solid waste (OFMSW) and to develop a simple method for simultaneous liquefaction and biofuels production. A model waste was prepared based on the composition of the organic waste in Masdar City. Chemical analysis of the OFMSW showed that it contained 37 % total solids with up to 57 g glucan/100 g total solid (TS). Hydrolysis of the wet OFMSW was carried out using a mix of hydrolytic enzymes: amylase, cellulase, protease, lipase, hemicellulase, and pectate lyase. The enzymatic hydrolysis using this enzyme mix was studied using different dilutions of the OFMSW at different enzyme loadings. This study has demonstrated that SSF of low severity pretreated OFMSW can be carried out using Saccharomyces cerevisiae without dilution (addition of water), and liquefaction of the undiluted OFMSW can be achieved in less than 24 h of hydrolysis. Also, SSF of the pretreated waste can be carried out with very low enzyme loading (10 % of the company recommended dosage)—0.1 % cellulase, 0.1 % amylase, 0.02 % protease, 0.02 % hemicellulase, 0.02 % lipase, and 0.02 % pectate lyase (w/w per TS) following mild heat pretreatment conditions of 85 °C for 1 h.

Straw of the halophyte Salicornia bigelovii was chemically analyzed for lignocellulosic components, extractives, and ash in relation to varying cultivation conditions (namely, irrigating water salinity and fertilizer grade). Irrigation water contained 10–50 ppt salt, and fertilizer application varied between 1 and 2 gN/m2. Composition of the biomass was comparable to traditional lignocellulosic biomasses, containing glucan (up to 27 g/100 g total solids (TS)), xylan (up to 23 g/100 g TS), and lignin (24 g/100 g TS), but also high amounts of ash (up to 53 g/100 g TS) and water–ethanol soluble extractives (up to 25 g/100 g TS). As most of the ash is extractable (up to 90%), a simple water wash is sufficient to bring the ash content down to a typical value found in the lignocellulosic materials. It was found that increasing water salinity used for the plant irrigation decreases lignocellulosic components content, increases ash content, and does not affect extractives content. The fertilizer application rate was not found to influence any of the responses, except for ash composition (lowering mineral content) and its amount in the flowering spike fraction. Stem and spike fractions were found to be significantly different in composition, with stems being closer to a typical lignocellulosic material.

Halophyte species of United Arab Emirates are a source of unique active phytochemicals, potentially due to the extreme environmental conditions under which the plants grow in the UAE. These phytochemicals make the native halophytes possibly interesting crops for biorefining, where biofuel production is combined with the production of value added chemicals, improving the economic feasibility of both process. Phytochemicals found in these species are widely recognized and researched as potential pharmaceutical and nutraceutical products. We reviewed the literature for secondary metabolites from species from the following halophyte families: Aizoaceae, Amaranthaceae (incl. Chenopodiaceae), Avicenniaceae, Zygophyllaceae. The review revealed that plant species belonging to these families contain valuable phytochemicals, such as fatty acids, terpenoids, flavonoids, alkaloids, steroids, tannins, saponins, quinones and coumarins, many of which have been reported to have therapeutic effects in humans.

The study focus was an examination of the hydrothermal pretreatment method applied to the lignocellulosic substrate, represented by the prairie cord grass, and comparison between different conditions based on the yield of glucose after enzymatic hydrolysis. The treatment did not involve any chemicals usage. Enzymatic hydrolysis was performed in order to examine the amount of glucose which was released from pretreated materials. The most efficient pretreatment conditions were at high temperature and relatively short reaction time (210°C and 10 min), after which the lignocellulose structure was the most available for enzymes actions which resulted in a pretreatment conversion rate of 97%. Temperature had a significant influence on glucose release during the hydrolysis, which was confirmed by the Michaelis-Menten and kinetic models. Kinetic models were used to fit the inhibitors and their conversion rates were related to temperature.

The purpose of this study was to fractionate switchgrass (SG) to obtain hemicellulose-, lignin-rich fractions and highly digestible pulp, using a clean fractionation (CF) approach. The main objective was to produce highest glucose yield in the enzymatic hydrolysis of pulp. Effects of processing factors such as time (10–50 min), temperature (120–160 °C), catalyst concentration (0.21–0.93% w/w sulfuric acid) and organic solvent mixture composition (7–43% w/w methyl isobutyl ketone) were evaluated. Response surface methodology and central composite design were used for process optimization and statistical analyses. High lignin (75–93%) and xylan (83–100%) removal from biomass were obtained, leaving solid pulp rich in glucan (78–94%). High enzymatic hydrolysis glucose yields (more than 90%) were obtained for selected optimal conditions. Pulp can be used for ethanol production while separated xylan and lignin fractions can be used as a feedstock for value-added products which suggests the applicability of clean fractionation technology in a biorefinery concept.

Prairie cordgrass (PCG) was pretreated by sequential extrusion and clean fractionation (CF) processing. Following CF, PCG was fractionated into cellulose, hemicellulose and lignin-rich fractions. Cellulose pulp was then enzymatically hydrolyzed, producing glucose. The main purpose of this study was to produce the highest glucose yield as possible. The effects of time, temperature, catalyst concentration and solvent mixture composition on the fractionation were tested. Different proportions of methyl isobutyl ketone (MIBK), ethanol and water with sulfuric acid as a catalyst were evaluated. Optimal conditions for sequential extrusion and clean fractionation (39 min, 129 °C, 0.69% catalyst, and 28% MIBK) resulted in higher glucose yield (92%), and more lignin (87%) and xylan (95%) removal than for clean fractionation alone. Pairwise comparison of raw PCG with extruded PCG clean fractionation revealed no difference in glucose yields, but xylan and AIL removal were higher in the case of clean fractionation of the pre-extruded PCG.

Switchgrass was used as a lignocellulosic feedstock for second generation ethanol production, after pretreatment using sulfuric acid-catalyzed modified clean fractionation based on NREL’s (National Renewable Energy Laboratory) original procedure. Optimization of temperature, catalyst concentration and solvent composition was performed using Response Surface Methodology, and 59.03 ± 7.01% lignin recovery, 84.85 ± 1.34% glucose, and 44.11 ± 3.44% aqueous fraction xylose yields were obtained at 140.00 °C, 0.46% w/w catalyst concentration, 36.71% w/w ethyl acetate concentration, and 25.00% w/w ethanol concentration. The cellulose fraction did not inhibit the fermentation performance of Saccharomyces cerevisiae and resulted in an ethanol yield of 89.60 ± 2.1%.

Lignin extracted from prairie cordgrass, switchgrass, and corn stover (using ethyl acetate–ethanol–water organosolv pretreatment) was analyzed and characterized using several methods. These methods included analysis of purity (by determination of Klason lignin, carbohydrate, and ash contents), solubility (with several organic solvents), phenolic group analysis (ultraviolet ionization difference spectra, and nitrobenzene oxidation), and general functional group analysis (by 1H NMR). Results showed that all the examined lignin samples were relatively pure (contained over 50% Klason lignin, less than 5% carbohydrate contamination, and less than 3% ash), but switchgrass-derived lignin was observed to be the purest. All the lignins were found to contain high amounts of phenolic groups, while switchgrass-derived lignin was the most phenolic, according to the ionization difference spectra. Nitrobenzene oxidation revealed that all the lignin samples contained available guaiacyl units in high amounts.

The main objective of this study was to fractionate prairie cordgrass (PCG) obtaining the highest cellulose digestibility. Following clean fractionation (CF) processing, the PCG lignocellulosic biomass was fractionated into three main building blocks: cellulose, hemicellulose and lignin. Effects of processing factors such as time, temperature, catalyst concentration and organic solvent mixture composition were evaluated. Organic solvent–aqueous mixture contained methyl isobutyl ketone (MIBK), ethanol and water in different proportions. Sulfuric acid was used as a catalyst. In order to evaluate the degree of pre-treatment, enzymatic saccharification was employed on the cellulose fraction obtained from the CF process. Response surface methodology was used for process optimization and statistical analysis. Optimal conditions (39 min, 154 °C, 0.69% catalyst and 9% MIBK) resulted in 84% glucose yield and 87% acid insoluble lignin (AIL).

The main purpose of this study was pretreatment of prairie cordgrass obtaining three fractions: lignin, hemicellulose and fermentable cellulose. Modified clean fractionation process (using ethyl acetate–ethanol–water mixture) was employed to extract lignin and hemicellulose fractions. Different proportions of constituents in the solvent mixture were tested. In order to improve lignin recovery, the process was catalyzed with sulfuric acid. Optimization was performed for fractionation processing conditions using lignin recovery and glucose yields as primary response variables. Optimal conditions resulted in a 51.33% lignin recovery, 53.82% hydrolysis glucose yield and 33.73% xylose yield in the aqueous fraction. To improve cellulose digestibility, solid fraction was subjected to hydrothermal post-treatment, for which optimal processing conditions were found, resulting in 78.93% hydrolysis glucose yield. This research represents a step forward for biomass pretreatment, and may open up new possibilities for utilization of prairie cordgrass.

A clean sequential process including clean fractionation and hydrothermal post-treatment was developed to fractionate and pretreat prairie cord grass (PCG) prior to ethanol fermentation. An optimized clean fractionation was applied to extract lignin; then, the remaining material was subjected to a hydrothermal treatment process to enhance cellulose digestibility. The main purpose of the hydrothermal post-treatment was to improve digestibility of delignified cellulose and reduce harshness of the clean fractionation process. Optimization was performed for solvent compositions as well as time and temperatures applied to each sequential process. The glucose yield was 89% from enzymatic hydrolysis and 92% from combined fractionation and hydrothermal treatments of PCG.

In this study, modified clean fractionation process was optimized for prairie cordgrass, with usage of alternative organic constituent –ethyl acetate. Other constituents of the solvent mixture included ethanol and water. Clean fractionation solvent was used in different proportions of the constituents. Process efficiency was determined by lignin recovery, solvent composition, as well as time and temperature applied to each sequential process. and overall pretreatment were calculated. Glucose yield during enzymatic hydrolysis Optimal conditions (125°C, 37 min, with the solvent composition of ester:ethanol:water = 32.5:22.5:45) yielded a 20% lignin recovery, 38% glucose yield during enzymatic hydrolysis and 26% xylose recovery in aqueous fraction.

The focus of this study was examination of the hydrothermal pretreatment method applied to the lignocellulosic substrate for bioethanol production, represented by prairie cord grass, and comparison between different conditions, based on the yield of glucose after enzymatic hydrolysis. The treatment did not involve any chemicals usage. Hydrothermal pretreatment was conducted in the Parr high-pressure reactor, in the presence of water. After the pretreatment, material was analyzed via high-performance liquid chromatography (HPLC) for products and scanning electron microscopy (SEM) for biomass structure changes. Enzymatic hydrolysis was performed to examine the amount of glucose that was released from pretreated materials. Results were compared based on the conversion rates of glucose and other sugars, as well as the generation of byproducts. Final results suggested that the most efficient pretreatment conditions involved high temperatures (210 °C) and relatively short reaction times (10 min), after which the lignocellulose structure seems to be the most available for enzymes actions. The pretreatment conversion rate in this case reached a level of 97%.