Influence of Homogenization Treatment on Physicochemical 4 Properties and Enzymatic Hydrolysis Rate of Pure 5 Cellulose Fibers

in Applied Biochemistry and Biotechnology (in press)

The aim of this study is to compare the effect of different homogenization treat- 12 ments on the physicochemical properties and the hydrolysis rate of a pure bleached 13 cellulose. Results obtained show ... [more ▼]

The aim of this study is to compare the effect of different homogenization treat- 12 ments on the physicochemical properties and the hydrolysis rate of a pure bleached 13 cellulose. Results obtained show that homogenization treatments improve the enzymatic 14 hydrolysis rate of the cellulose fibers by 25 to 100 %, depending of the homogenization 15 treatment applied. Characterization of the samples showed also that homogenization had an 16 impact on some physicochemical properties of the cellulose. For moderate treatment inten- 17 sities (pressure below 500 b and degree of homogenization below 25), an increase of water 18 retention values (WRV) that correlated to the increase of the hydrolysis rate was highlighted. 19 Result also showed that the overall crystallinity of the cellulose properties appeared not to be 20 impacted by the homogenization treatment. For higher treatment intensities, homogenized 21 cellulose samples developed a stable tridimentional network that contributes to decrease 22 cellulase mobility and slowdown the hydrolysis process. [less ▲]

Influence of steam explosion on physico-chemical properties and hydrolysis rate of pure cellulose fibers

in Bioresource Technology (2012), 121(221-227),

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that ... [more ▼]

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not improve the enzymatic hydrolysis rate of the cellulose fibers. The characterization of the obtained samples showed an increase of the cellulose accessibility coupled with an increase of the overall crystallinity of the substrate. In these conditions, the higher accessibility is counterbalanced by the increased crystallinity. Indeed, a greater proportion of the substrat is accessible by only a fraction of the enzymatic complex (exo-glucanases) activities. When the severity factor reached 5.2, a decrease of the cellulose enzymatic hydrolysis rate was observed. In this case, TGA analysis showed an increase of the char level at the end of the pyrolysis which traduced an important thermal degradation of the samples. The thermal degradation of cellulose lead to an important change in substrate composition, which induced a decrease of the cellulose ratio available for hydrolysis and caused a decrease of the hydrolysis yields. [less ▲]

Optimization of a formic/acetic acid treatment of beech wood for lignin extraction

Conference (2012, August)

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of ... [more ▼]

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of cellulose (into fermentable glucose) constituted the central axis of lignocellulosic biorefinery processes. Degraded hemicelluloses and lignins were recovered as side-products with no possibilities of high-added value applications. Within the context of an integrated biorefinery, and for economic reasons, the recovery and the non-energetic valorization of lignins have opened recently new horizons. Lignin is a cross-linked phenolic polymer and is considered as potential alternative to petrochemical polymers or as a source of antioxidants for cosmetics and food industry, resins, chelating agent... As the final application of lignin depends on both extraction process and type of lignocellulosic sources, the development of fast and efficient physicochemical characterization methods is thus a prerequisite to optimize extraction processing conditions. In this study, beech wood particles (Fagus sylvatica L.) are delignified at atmospheric pressure by a formic acid/acetic acid/water mixture. Firstly, response surface methodology is used to optimize cooking time and temperature for delignification, pulp yield and concentration of degradation products (2-furfural and 5-hydroxymethylfurfural). The results highlight that best delignification is obtained in the highest cooking times and temperatures and that 5-hydroxymethylfurfural is produced during the formic/acetic acid treatment but is also degraded into 2-furfural. With the aim to develop an integrated biorefinery approach, multi-criteria optimization is used to find ideal cooking time and temperature (5h07, 104.2°C) leading to the maximization of delignification and pulp yield and to the minimization of 2-furfural production Finally, physicochemical and chemical structures of extracted lignins are found dependent on treatment conditions harshness. [less ▲]

STEAM EXPLOSION : PROCESS AND IMPACT ON LIGNOCELLULOSIC MATERIAL

Poster (2012, March 01)

Steam explosion is a thermomechanochemical process which allows the breakdown of lignocellulosic structural components by steam heating, hydrolysis of glycosidic bonds by organic acid formed during the ... [more ▼]

Steam explosion is a thermomechanochemical process which allows the breakdown of lignocellulosic structural components by steam heating, hydrolysis of glycosidic bonds by organic acid formed during the process and shearing forces due to the expansion of the moisture. The process is composed of two distinct stages: vapocracking and explosive decompression. Cumul effects of both phases include modification of the physical properties of the material (specific surface area, water retention capacities, color, cellulose crystallinity rate,…), hydrolysis of hemicellulosic components (mono and oligosaccharides released) and modification of the chemical structure of lignin. These effects permit the opening of lignocellulosic structures and increase the enzymatic hydrolysis rate of cellulose components in the aim to obtain fermentable sugars used in second generation biofuels process. [less ▲]

Effect of physicochemical characteristics of cellulosic substrates on enzymatic hydrolysis by means of a multi-stage process for cellobiose production

in Applied Biochemistry and Biotechnology (2012), 166(6), 1423-1432

The effect of two types of cellulose, microcrystalline cellulose and paper pulp, on enzymatic hydrolysis for cellobiose production was investigated. The particle size, the relative crystallinity index and ... [more ▼]

The effect of two types of cellulose, microcrystalline cellulose and paper pulp, on enzymatic hydrolysis for cellobiose production was investigated. The particle size, the relative crystallinity index and the water retention value were determined for both celluloses. A previously studied multistage hydrolysis process that proved to enhance the cellobiose production was studied with both types of celluloses. The cellobiose yield exhibited a significant improvement (120% for the microcrystalline cellulose and 75% for the paper pulp) with the multistage hydrolysis process compared to continuous hydrolysis. The conversion of cellulose to cellobiose was greater for the microcrystalline cellulose than for the paper pulp. Even with high crystallinity, microcrystalline cellulose achieved the highest cellobiose yield probably due to its highest specific surface area accessible to enzymes and quantity of adsorbed protein. [less ▲]

Impact of formic/acetic acid and ammonia pre-treatments on chemical structure and physico-chemical properties of Miscanthus x giganteus lignins

in Polymer Degradation & Stability (2012), 96(10), 1761-1770

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 C and 80° C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 C. The effects of these ... [more ▼]

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 C and 80° C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 C. The effects of these fractionation processes on chemical structure, physico-chemical properties and antioxidant activity of extracted lignins were investigated. Lignins were characterized by their purity, carbohydrate composition, thermal stability, molecular weight and by Fourier transform infrared (FTIR), 1H and quantitative 13C nuclear magnetic resonance (NMR), adiabatic broadband {13C-1H} 2D heteronuclear (multiplicity edited) single quantum coherence (g-HSQCAD). The radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) was also investigated. Formic/acetic acid pretreatment performed in milder conditions (80° C for 3 h) gave a delignification percentage of 44.7% and soaking in aqueous ammonia 36.3%. Formic/acetic acid pretreatment performed in harsh conditions (107°C for 3 h) was more effective for extensive delignification (86.5%) and delivered the most pure lignin (80%). The three lignin fractions contained carbohydrate in different extent: 3% for the lignin obtained after the formic/acetic acid pretreatment performed at 107 C (FAL-107), 5.8% for the formic/acetic acid performed at 80°C (FAL-80) and 13.7% for the ammonia lignin (AL). The acid pretreatment in harsh conditions (FAL-107) resulted in cleavage of b-O-4' bonds and aromatic C-C. Repolymerisation was thought to originate from formation of new aromatic C-O linkages. Under milder conditions (FAL-80) less b-O-4' linkages were broken and repolymerisation took place to a lesser extent. Ammonia lignin was not degraded to a significant extent and resulted in the highest weight average 3140 g mol -1. Despite the fact of FAL-107 repolymerisation, significant phenolic hydroxyls remained free, explaining the greater antioxidant activity. [less ▲]

Influence des traitements de steam explosion sur la dégradation thermique des fibres de cellulose

Poster (2011, December)

La présente étude a pour but d’identifier l’impact de différents traitements de steam explosion sur les propriétés de dégradation thermique des fibres de cellulose. Dans un premier temps, les intensités ... [more ▼]

La présente étude a pour but d’identifier l’impact de différents traitements de steam explosion sur les propriétés de dégradation thermique des fibres de cellulose. Dans un premier temps, les intensités des traitements appliqués ont été définies sur base d’un facteur de sévérité (SF), établi par une corrélation entre le temps de séjour et la température du process. Les résultats obtenus montrent que la dégradation thermique des fibres de cellulose reste limitée lorsque la valeur du facteur de sévérité est inférieure à 4.0. Aux intensités supérieures, le dosage des produits de dégradation montre une croissante importante des concentrations en hydroxyméthylfurfurals (5-HMF) dans les phases liquides issues des différents traitements. Lorsque la valeur du facteur de sévérité dépasse 5.2, les analyses TGA indiquent que l’augmentation des produits de dégradation est couplée à une croissance importante du taux de résidus carbonés, indiquant une forte dégradation thermique de la cellulose [less ▲]

Effect of steam explosion pre-treatment on enzymatic saccharification of lignocellulosic material

Poster (2011, September 08)

Taking into account the sharp rise in prices and the depletion of resources of petroleum, an alternative to fossil resources is needed. A probable alternative is the use of lignocellulosic raw material to ... [more ▼]

Taking into account the sharp rise in prices and the depletion of resources of petroleum, an alternative to fossil resources is needed. A probable alternative is the use of lignocellulosic raw material to produce biofuels. The “first generation” biofuels are highly controversial because of the use of food plant material. The aim of the “second generation” biofuels is to take lignocellulosic non-food plant material as raw material. Lignocellulosic biomass has a very complex structure made of linkages between lignins, cellulose and hemicelluloses. The saccharification of these lignocellulosic materials requires the fractionation of its constituents. Research has lead to many lignocellulosic biomass fractionation pre-treatments. This study particularly focuses on the steam explosion pretreatment followed by an enzymatic saccharification. Steam explosion is a thermomechanical process which allows the breakdown of the lignocellulosic material structure by the combined action of steam heating, hydrolysis induced by the organic acids formed during the process and shear stress resulting from the pressure rough drop. This treatment leads to modification of the physical parameters such as water retention capacity, cristallinity rate of the cellulosic fraction, hydrolysis of the hemicellulosic fraction and rearrangement in the lignin structure. Such modifications are supposed to make cellulose enzymatic hydrolysis from complex lignocellulosic material easier. In order to verify this hypothesis, different lignocellulosic raw materials have been pre-treated by steam explosion. These materials were sugar beet pulp, corn straw and miscanthus. In order to check the effect of steam explosion pre-treatment on cellulose, a microcrystalline cellulose was also treated. Steam explosion was performed at a vapor pressure of 18 bars and with a retention time of 2 minutes. The steam exploded lignocellulosic materials and the untreated one were submitted to a hydrolysis with a mixture of enzymes composed of cellulases and cellobiase activities during 24 hours. The quantification of glucose in the hydrolysates at different times was performed by HPAEC-PAD. Rate of cellulose converted into glucose were better with steam exploded raw material showing that steam explosion allows improvement of lignocellulosic material for enzymatic saccharification. [less ▲]

Study on the susceptibility of the bovine milk fat globule membrane proteins to enzymatic hydrolysis and organization of some of the proteins

in International Dairy Journal (2011), 21(5), 312-318

Isolated milk fat globules were subjected to enzyme hydrolysis by a specific protease (trypsin) and a nonspecific protease (pronase E) to study the asymmetric arrangement of milk fat globule membrane ... [more ▼]

Isolated milk fat globules were subjected to enzyme hydrolysis by a specific protease (trypsin) and a nonspecific protease (pronase E) to study the asymmetric arrangement of milk fat globule membrane (MFGM) proteins. The remaining proteins on the globules after proteolysis were resolved by two-dimensional gel electrophoresis and identified by mass spectrometry. By this proteomic approach, the results confirmed different susceptibility of the MFGM proteins to proteolysis by enzymes. Butyrophilin and adipophilin were completely digested by trypsin and by pronase E, whereas lactadherin and xanthine dehydrogenase/oxidase were almost resistant to hydrolysis by trypsin and partially attacked by pronase E. Based on our results and recent bibliographic data, an up-dated model of the organization of some MFGM proteins is proposed and discussed. (c) 2011 Elsevier Ltd. All rights reserved. [less ▲]

Impact of a formic/acetic acid treatment of beech wood on delignification and chemical structure of lignins

Conference (2011)

Lignocellulosic substrates constitute a promising alternative resource for the sustainable production of energy (biofuels), biobased products and organic compounds. In the past, the extraction and the ... [more ▼]

Lignocellulosic substrates constitute a promising alternative resource for the sustainable production of energy (biofuels), biobased products and organic compounds. In the past, the extraction and the valorization of cellulose (into fermentescible glucose) constituted the central axis of lignocellulosic biorefinery processes. Degraded hemicelluloses and lignins were however recovered as side-products with no possibilities of high-added value applications. Within the context of an integrated biorefinery, and for economic reasons, the recovery and the non-energetic transformation of lignins have opened recently new horizons. Lignin is a cross-linked phenolic polymer and is considered as a potential alternative to petrochemical polymers or as a source of antioxidants for cosmetics and food industry, resins, chelating agent... As the final application of lignin is dependent of both extraction process and type of lignocellulosic sources, the development of fast and efficient physicochemical characterization methods is thus a prerequisite to optimize extraction processing conditions. In this study, beech wood particles (Fagus sylvatica L.) collected in the region of Gaume (Belgium) were delignified at atmospheric pressure by a mixture of formic acid/acetic acid/water. The effect of cooking time and temperature was evaluated on delignification and on chemical structure of lignins obtained by precipitation from the black liquor after treatments. To study the delignification, a central composite design and response surface methodology were used for the optimization of two treatments parameters, i.e. time (between 1h30 and 4h30) and temperature (from 87 to 107°C). These two variables were optimized for delignification yield, pulp yield, concentration of degradation products (furfural and hydroxymethylfurfural) and for the amount of residual linkages between lignin constitutive units. On the basis of our results, higher delignification yields were obtained when cooking time and temperature increased. However, for high cooking times and temperatures, pulp yield decreased because hemicelluloses and cellulose were hydrolyzed and the production of furfural and hydroxymethylfurfural was augmented. The structural and physico-chemical features of extracted lignins were investigated with different analytical tools, namely infrared spectrometry, thermogravimetric analysis, size-exclusion chromatography, mono-dimensional nuclear magnetic resonance (NMR 1H and NMR 13C) and bidimensional NMR (heteronuclear HSQC experiments). The characterization of lignins indicated the occurrence of a repolymerization phenomenon when both cooking time and temperature increased. Indeed, HSQC NMR spectra presented oxidized syringyl units. Otherwise, thermogravimetric analysis and HSQC analysis showed the presence of hemicelluloses in lignin samples from soft treatments (1h30, 87°C). Some linkages between lignin and hemicelluloses were not cleaved under these experimental conditions. [less ▲]