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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.

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%.