Jürgen Andreaus

Pre-treatment of lignocellulosic biomass using ionic liquids: wheat straw fractionation.

This work is devoted to study pre-treatment methodologies of wheat straw with 1-ethyl-3-methylimidazolium acetate ([emim][CH3COO]) and subsequent fractionation to cellulose, hemicellulose and lignin. The method developed and described here allows the separation into high purity carbohydrate and lignin fractions and permits an efficient IL recovery. A versatility of the established method was confirmed by the IL reuse. The fractionation of completely dissolved biomass led to cellulose-rich and hemicellulose-rich fractions. A high purity lignin was also achieved. To verify the potential further applicability of the obtained carbohydrate-rich fractions, and to evaluate the pre-treatment efficiency, the cellulose fraction resulting from the treatment with [emim][CH3COO] was subjected to enzymatic hydrolysis. Results showed a very high digestibility of the cellulose samples and confirmed a high glucose yield for the optimized pre-treatment methodology.

Current Pretreatment Technologies for the Development of Cellulosic Ethanol and Biorefineries.

Lignocellulosic materials, such as forest, agriculture, and agroindustrial residues, are among the most important resources for biorefineries to provide fuels, chemicals, and materials in such a way to substitute for, at least in part, the role of petrochemistry in modern society. Most of these sustainable biorefinery products can be produced from plant polysaccharides (glucans, hemicelluloses, starch, and pectic materials) and lignin. In this scenario, cellulosic ethanol has been considered for decades as one of the most promising alternatives to mitigate fossil fuel dependence and carbon dioxide accumulation in the atmosphere. However, a pretreatment method is required to overcome the physical and chemical barriers that exist in the lignin-carbohydrate composite and to render most, if not all, of the plant cell wall components easily available for conversion into valuable products, including the fuel ethanol. Hence, pretreatment is a key step for an economically viable biorefinery. Successful pretreatment method must lead to partial or total separation of the lignocellulosic components, increasing the accessibility of holocellulose to enzymatic hydrolysis with the least inhibitory compounds being released for subsequent steps of enzymatic hydrolysis and fermentation. Each pretreatment technology has a different specificity against both carbohydrates and lignin and may or may not be efficient for different types of biomasses. Furthermore, it is also desirable to develop pretreatment methods with chemicals that are greener and effluent streams that have a lower impact on the environment. This paper provides an overview of the most important pretreatment methods available, including those that are based on the use of green solvents (supercritical fluids and ionic liquids).

Characterization of the Cellulase Complex of Penicillium echinulatum

New cellulases from a strain of Penicillium echinulatum were characterized for their filter paper activity and β-glucosidase activity. Both activities showed maximum values between pH 4 and 5. With citrate buffer, activities were slightly higher than in acetate buffer of the same pH. Thermal stability of both activities was good up to 55°C. Filter paper activity was significantly reduced at higher temperatures.

Effects of temperature on the cellulose binding ability of cellulase enzymes

The effects of high temperatures on catalytic activity and binding abilities of crude Trichoderma reesei cellulases in solution and adsorbed to a cotton fabric were studied. Above optimum temperature of 508C, catalytic activities were severely diminished but the binding behaviour was not found to be adversely affected. In order to verify possible applications of cellulases adsorbed to cotton fabrics as anchors for textile finishing purposes, we also checked the binding abilities after ironing. Previous ironing of cellulase adsorbed fabrics increased dyeability with an acid dye, but dye fastness was poor. Desorption of cellulases from cotton fabrics increased from pH 5 to pH 10. Dry ironing of fabrics resulted in less desorption, whereas wet ironing inhibited desorption at pH 5 and only 11% of protein were desorbed at pH 10. Ironing of the fabrics diminished enzyme activity of desorbed cellulases. Wet ironing resulted in complete denaturation of the proteins and no cellulolytic activity was found. The presence of water during thermal treatment of cellulases was found to be essential for complete denaturation and unfolding of the proteins. Dry heat only resulted in partial denaturation. Fluorescence measurements of cellulases adsorbed to cotton fabrics showed after ironing a significant shift in tryptophan fluorescence to higher wavelengths. This indicates unfolding and denaturation of the enzymes and revelation of more hydrophobic amino acids to the surface, which enables increased hydrophobic interactions with the fabric. q 1999 Elsevier Science B.V. All rights reserved. .

Influence of Cellulases on Indigo Backstaining

We have found that increasing concentrations of fungal cellulases on a fabric decrease indigo staining levels. Deletion of the cellulose binding domains (CBD) from either bacterial or fungal cellulases decreases indigo staining levels and generally causes less backstaining than the entire enzyme. Increasing the concentration of cellulases with a CBD of family I on fabric decreases indigo staining, whereas increasing the concentration of cellulase with a CBD of family II has no effect on staining. After-washing experiments of indigo-stained cotton fabrics show that it is easier to remove indigo adsorbed on cellulase adsorbed onto cotton than indigo directly adsorbed onto cotton.

A green and efficient approach to selective conversion of xylose and biomass hemicellulose into furfural in aqueous media using high-pressure CO2 as a sustainable catalyst

This work introduces a novel approach to produce furfural from lignocellulosic biomass without the use of mineral acids or heterogeneous catalysts. The proposed concept consists of two reaction stages. The first one consists of an extraction of hemicellulose from wheat straw using high-pressure CO2 and H2O to produce a water-soluble fraction containing pentoses in oligomeric and monomeric forms. The second step involves the conversion of this fraction into furfural in a system consisting of water, tetrahydrofuran (THF), methyl isobutyl ketone (MIBK) and high-pressure CO2 at elevated temperatures with MIBK as the water immiscible extracting solvent. At 200 °C and 50 bar of initial CO2 pressure, the high-pressure CO2 and H2O assisted process of hemicellulose extraction resulted in 81 mol% conversion of hemicellulose into xylose and arabinose (mainly as oligomers). Prior to the use of the produced hemicellulose hydrolysate in dehydration reactions to obtain furfural, a series of preliminary trials with xylose, as a model compound, were performed. The biphasic system with water/THF/MIBK under the reaction conditions with 50 bar of initial CO2 pressure, at 180 °C, 60 min favoured the production of furfural and allowed to obtain furfural at a yield and selectivity of 56.6 mol% and 62.3 mol%, respectively. Under the same conditions, hemicellulose hydrolysate dehydration yielded 43 mol% of furfural with a selectivity of 44 mol%.

The application of catalase for the elimination of hydrogen peroxide residues after bleaching of cotton fabrics.

Results of dyeing of cotton fabrics with a bifunctional reactive dye were significantly improved when the fabric after bleaching with hydrogen peroxide was treated with catalase for the elimination of hydrogen peroxide residues from the fabrics. Compared to processes with a varying number of washing steps, with and without commercial reducing agents, the consumption of water could be significantly reduced, without altering the final color shade.

Application of cellulases from Acrophialophora nainiana and Penicillium echinulatum in textile processing of cellulosic fibres

New cellulases from the fungi Acrophialophora nainiana and Penicillium echinulatum were used in the finishing of knitted cotton fabrics (biopolishing) and compared with the well established enzymes from Trichoderma reesei. Both cellulases reduced the pilling tendency with a lower weight loss than T. reesei cellulases. Cellulases from P. echinulatum were also studied in stonewashing of denim fabrics to obtain the fashionable aged look in indigo dyed jeans ware and were found to remove more colour from denim fabrics and produce less indigo dye redeposition (back-staining) than commercial acid or neutral cellulases under the test conditions. Efficiency was found to be influenced by pH during textile processing and the substrate used for the production of cellulases. Cellulases produced by P. echinulatum grown on cellulose showed better stonewashing results (higher colour removal and less back-staining) than cellulases produced on sugar cane bagasse. The substrate used during enzyme production of P. echinulatum cellulases seems to have a significant influence on cellulose composition, which affects textile processing results.

High-pressure carbon dioxide/water pre-treatment of sugarcane bagasse and elephant grass: Assessment of the effect of biomass composition on process efficiency

The performance of two lignocellulosic biomasses was studied in high-pressure carbon dioxide/water pre-treatment. Sugarcane bagasse and elephant grass were used to produce C5-sugars from hemicellulose and, simultaneously, to promote cellulose digestibility for enzymatic saccharification. Different pre-treatment conditions, with combined severity factor ranging from -1.17 to -0.04, were evaluated and maximal total xylan to xylose yields of 59.2wt.% (34.4wt.% xylooligomers) and 46.4wt.% (34.9wt.% xylooligomers) were attained for sugarcane bagasse and elephant grass, respectively. Furthermore, pre-treated biomasses were highly digestible, with glucan to glucose yields of 77.2mol% and 72.4mol% for sugarcane bagasse and elephant grass, respectively. High-pressure carbon dioxide/water pre-treatment provides high total C5-sugars and glucose recovery from both lignocellulosic biomasses; however it is highly influenced by composition and intrinsic features of each biomass. The obtained results confirm this approach as an effective and greener alternative to conventional pre-treatment processes.

Decolorization of aqueous solutions of disperse textile dyes by oxidoreductases

The potential of three oxidoreductases, a laccase preparation of Pleurotus sajor-caju PS-2001, horseradish peroxidase (HRP) and a microbial peroxidase (MP) was evaluated for the decolorization of disperse textile dyes (CI Disperse Red 343, CI Disperse Red 167 and CI Disperse Blue 148) used in polyester dyeing. Decolorization was studied in aqueous solutions varying in dye concentration, pH, temperature, enzyme concentration and the addition of mediators HBT and syringaldazine. The best conditions found for Disperse Red 343 with laccase, HRP and MP were: 15 mg L−1 dye concentration, 50°C, pH 3.0 for laccase and pH 5.0 for peroxidases. Without mediator, the highest decolorizaton results (38.5% and 58.6%) were achieved with the highest tested concentrations of laccase (10 U mL−1) and HRP (89.7 U mL−1), respectively, but no significant difference in decolorization was found for the tested MP concentrations (29.9–89.7 U mL‐1). HBT or syringaldazine increased decolorization with peroxidases significantly, but no effect was observed for the laccase. Decolorization of Disperse Red 167 (up to 15%) and Disperse Blue 148 (up to 25%) was much lower than of Disperse Red 343. With respect to enzyme concentration, the use of mediator and under the selected test conditions the laccase of P. sajor-caju PS-2001 turned out to be more efficient in disperse dye decolorization, than peroxidases HRP and MP.