Depolymerization of fractionated wood by hydrothermal liquefaction

Direct thermochemical conversion of lignocellulosic biomass produces a mixture of compounds that have to be separated to produce purified building blocks. Moreover, lignin derived products have a detrimental effect on further biological conversion processes, such as fermentation. For all these reasons, it is important to develop an integrated approach for a better fractionation and valorisation of macromolecules (carbohydrates and lignin) in bio-refineries. Please click Additional Files below to see the full abstract

Batch fermentation of d-glucose/cellobiose mixtures by clostridium acetobutylicum atcc 824: energetic and carbon source regulation

Lignocellulosic biomass presents an interesting alternative to fossil carbon sources as a source of renewable energy that respects the environment. Indeed, this abundant resource can be converted by a wide range of thermal, chemical and biological techniques to compounds that can be used as substrate in anaerobic fermentation to produce biofuels and building blocks. As a general rule, micro-organisms possess regulation mechanisms that ensure the sequential use of the carbon and energy sources present in their environment. These regulations may consequently play a vital role in biomass to energy and building blocks conversion performances. Clostridium acetobutylicum, a promising biomass transformation organism, has the capacity to utilize a wide variety of compounds as carbon and energy sources. These compounds may be present in a complex mixture produced from cellulose conversion. Therefore it is of high importance to understand the potential synergy or inhibiting effects of the cellulose-derived products. The aim of this work is to study this regulation mechanism by using glucose and cellobiose as model substrates, provided alone and in mixtures to Clostridium acetobutylicum. Our experiments show a total consumption of both substrates, alone or in mixtures, with an increment of 30% of microbial growth production of cellobiose over glucose. A diauxic growth (cell growth in two phases) occurs in the presence of different mixtures of D-glucose and cellobiose. In general, D-glucose is the preferred substrate and after its complete consumption, when exhausted, the growth kinetics exhibits an adaptation time, of approximately 1-2 hours, before to be able to use cellobiose (figure 1). This adaptation is probably due to an induction stage that is also accompanied of acid consumption (lactic acid). This study provides a first approach to understand the metabolic changes related to substrate utilization in Clostridia. Please click Additional Files below to see the full abstract

Cellulose valorization in biorefinery: integration of fast pyrolysis and fermentation for building blocks production

A combination of thermochemical and biological conversion of cellulosic materials is a promising alternative for the production of biofuels and building blocks in an integrated biorefinery. Indeed, enzymatic depolymerization is selective but slow and expensive. It would be of interest to associate thermochemical conversion for a fast depolymerization of biomass with biochemical conversion for a selective conversion of depolymerized liquid streams. In this work, cellulose is pyrolyzed to produce sugars that can be used as substrate for a fermentation process. This work is the result of a scientific collaboration between ICFAR (London, Canada) and CNRS (Nancy, France). Pyrolysis was performed in a fluidized bed reactor at 475ᵒC with a bio-oil yield of 73.4 wt.% (Figure 1). Different fractions of bio-oil were recovered with a set of 5 condensers. Levoglucosan and total sugars were quantified by GC-FID-MS and phenol/sulphuric acid method respectively. The maximum yields of levoglucosan (43.7 %) and total sugars (80.4 %) were found in the first condenser that was kept at 70ᵒC. Due to the non-fermentable condition of levoglucosan, all the oil fractions, as well as a mixture of them, were hydrolyzed to obtain fermentable glucose. The different bio-oil fractions and a mixture of all fractions were used as substrate in a fermentation reactor to produce acetone, butanol and ethanol (ABE). The talk will present the mass yields obtained for the integrated process combining pyrolysis, hydrolysis and fermentation (figure 2). The microorganisms were not able to grow in the mixture of all fractions. On the contrary, fractions from condenser 1 and 2 lead to normal bacterial growth and fermentation products pattern. Maximum yields (per gram of oil) of acetone=4.6 %, butanol=13.2 % and ethanol=0.1 % were found for the bio-oil collected in the first condenser. These results put in evidence the importance of pyrolysis with staged condensation as an entry for fermentation processes. The methodology proposed in this work could be applied to other biochemical conversion of bio-oils to produce higher added-value products. Please click Additional Files below to see the full abstract

Valorisation de la cellulose dans une bioraffinerie : synergies entre les procédés thermochimiques et biologiques

Because fossil resources are exhaustible by definition, the carbon needed for energy and materials production could be obtained from lignocellulosic biomass. Fermentation processes are able to provide a wide variety of interesting products that can replace the crude oil based "building blocks". However, the abundance of lignocellulosic biomass in the environment contrasts with its very low bioavailability. Indeed, because of (i) its insoluble nature, (ii) its more or less crystalline structure and (iii) the nature of the bonds between the polymer fibers, cellulose is a carbon substrate difficult to valorize by biochemical/fermentation processes alone. Fast pyrolysis or liquefaction of cellulose are mainly studied to produce a bio-oil, which would be upgraded by catalytic hydrotreatment into fuels or building blocks. In the current state of the art, studies at the interface of these two fields involving a biochemical or microbiological conversion of these bio-oils are still rare. The aim of this thesis is the coupling of a thermochemical conversion process of cellulose, to depolymerize it, to a microbial transformation process to produce solvents, acids and gases (butanol, ethanol, acetone, acetic acid, butyric acid, lactic acid, hydrogen) that are of great interest for the fuel or green chemistry industry. To do this, beech wood was fractionated by organosolv and chlorite / acid (SC / AA) methods in order to recover a cellulose-rich pulp. Hydrothermal liquefaction and fast pyrolysis processes were used to obtain sugars that were transformed into building blocks by fermentation. Many analytical methods have been developed for the characterization of products from each step of the process. Finally, a model of the process using the commercial software Aspen Plus® was developed to establish mass and energy balances of the integrated process including: the fractionation of the wood, then the liquefaction of the cellulosic fraction and the fermentation of bio-oilsParce que les ressources fossiles sont épuisables par définition, le carbone nécessaire à la production d'énergie et de matériaux pourrait provenir en grande partie de la biomasse lignocellulosique. Les procédés de fermentation sont capables de fournir une grande variété de produits d'intérêts capables de remplacer les synthons d'origine pétrolière. Cependant, en raison (i) de son caractère insoluble, (ii) de sa structure plus ou moins cristalline et (iii) de la nature des liaisons entre les maillons du polymère, la cellulose est un substrat carboné difficile à valoriser par voie biochimique/fermentaire seule. La pyrolyse rapide ou la liquéfaction de la cellulose sont principalement étudiées pour produire une bio-huile, qui serait valorisée par hydrotraitement catalytique en carburant ou en building blocks. Dans l'état de l'art actuel, les travaux à l'interface de ces deux domaines portant sur une conversion biochimique ou microbiologique de ces bio-huiles sont encore rares. L’objectif de cette thèse est de coupler un procédé de conversion thermochimique de la cellulose, pour la dépolymériser, à un procédé de transformation microbienne pour produire des solvants, des acides et des gaz (butanol, éthanol, acétone, acide acétique, acide butyrique, acide lactique, hydrogène) qui suscitent un fort intérêt dans l’industrie des carburants ou de la chimie verte. Pour ce faire, le bois de hêtre a été fractionné par les méthodes organosolv et chlorite/acide (SC/AA) afin de récupérer une pâte riche en cellulose. Des procédés de liquéfaction hydrothermale et de pyrolyse rapide ont été utilisés pour obtenir des sucres qui ont été finalement transformés par fermentation en synthons. De nombreuses méthodes analytiques ont été développées pour la caractérisation des produits issus de chaque étape du procédé. Enfin, un modèle du procédé utilisant le logiciel commercial Aspen Plus® a été développé pour établir les bilans de matière et énergie du procédé intégré : du fractionnement du bois, puis la liquéfaction de la fraction cellulosique et à la fermentation des bio-huile

Importance of lignin removal in enhancing biomass hydrolysis in hot-compressed water

International audienc

Diauxic growth of Clostridium acetobutylicum ATCC 824 when grown on mixtures of glucose and cellobiose

Abstract Clostridium acetobutylicum, a promising organism for biomass transformation, has the capacity to utilize a wide variety of carbon sources. During pre-treatments of (ligno) cellulose through thermic and/or enzymatic processes, complex mixtures of oligo saccharides with beta 1,4-glycosidic bonds can be produced. In this paper, the capability of C. acetobutylicum to ferment glucose and cellobiose, alone and in mixtures was studied. Kinetic studies indicated that a diauxic growth occurs when both glucose and cellobiose are present in the medium. In mixtures, d-glucose is the preferred substrate even if cells were pre grown with cellobiose as the substrate. After the complete consumption of glucose, the growth kinetics exhibits an adaptation time, of few hours, before to be able to use cellobiose. Because of this diauxic phenomenon, the nature of the carbon source deriving from a cellulose hydrolysis pre-treatment could strongly influence the kinetic performances of a fermentation process with C. acetobutylicum

Hydrothermal conversion of wood, organosolv and chlorite pulps

International audienc

Decomposition of Cellulose in Hot-Compressed Water: Detailed Analysis of the Products and Effect of Operating Conditions

Understanding the reaction pathways of cellulose hydrolysis in hot-compressed water (HCW) is crucial for the optimization of fermentable sugar and chemical production. Advanced analytical strategies are required to better assess the wide range of products from cellulose conversion in HCW. In this work, cellulose conversion in HCW was conducted in an autoclave with sampling upon the reaction time under isothermal conditions (180, 220, and 260 °C from 0 to 120 min). Total water-soluble carbohydrates were quantified (phenol/sulfuric acid method). These products were first characterized by size-exclusion chromatography coupled to evaporative light scattering detection and mass spectrometry (SEC–ELSD–MS). SEC is useful for screening the molecular weight distribution of soluble products. Then, the chemical structure of water solubles has been attributed by hydrophilic interaction liquid chromatography coupled to a linear trap quadrupole Orbitrap mass spectrometer (HILIC–LTQ–Orbitrap–MS). This method notably provides evidence of the formation of a cellobiose conformer under some HCW conditions. A specific high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC–PAD) method has been developed. This method allows for a selective separation of 5-hydroxymethylfurfural (5-HMF), glucose, fructose, mannose, and oligomers up to cellopentaose. Carboxylic acids were quantified by high-performance liquid chromatography with ultraviolet detection (HPLC–UV). Solid residues obtained after HCW conversion were characterized by X-ray diffraction (XRD) and permanent gas by micro-gas chromatography. The global reaction mechanism of cellulose liquefaction in HCW is rationalized on the basis of these complementary methods. Cellulose conversion first proceeds with heterogeneous hydrolysis (fiber surface) to produce soluble oligomers in competition with pyrolysis (inner fibers with limited mass transfer of water), producing levoglucosan (promoted at a higher temperature). Soluble oligomers produce glucose and isomers by homogeneous hydrolysis (liquid phase). C₆ sugars can then undergo further conversion to produce notably 5-HMF and erythrose

Fast Pyrolysis of Heartwood, Sapwood, and Bark: A Complementary Application of Online Photoionization Mass Spectrometry and Conventional Pyrolysis Gas Chromatography/Mass Spectrometry

Wood offers important potential for biofuel or chemical production by fast pyrolysis but exhibits variable chemical composition that impacts pyrolysis product composition. Here, fast pyrolysis of heartwood, sapwood, and bark isolated from Douglas fir (softwood) and oak (hardwood) was studied by a microfluidized bed reactor (MFBR) combined with single photoionization mass spectrometry (SPI–MS) to provide insights into the wood zone effects on the composition of pyrolysis volatiles. The difference in pyrolysis volatile composition has been clearly unraveled by principle component analysis (PCA) based on the major ions detected by SPI–MS. Some specific product markers have been defined for each wood zone (heartwood, sapwood, and bark) and related to the chemical composition of wood samples (lignin, carbohydrates, and minerals). The catalytic effect of minerals (notably potassium) has a higher impact on carbohydrate decomposition than on lignin decomposition for a given wood type. Therefore, sapwood and heartwood (for both oak and Douglas fir) can be clearly discriminated by specific markers mainly from carbohydrate pyrolysis. Interestingly, our results show that the wood cylinders exhibit a more marked wood zone effect on product compositions compared to fine powders. SPI–MS results were further compared to those of pyrolysis gas chromatography/mass spectrometry (Py–GC/MS), and many of them are consistent. MFBR combined with SPI–MS is a selective analytical technique to figure out the effect of wood composition on pyrolysis volatiles