A novel hybrid organosolv: steam explosion method for the efficient fractionation and pretreatment of birch biomass

Background: The main role of pretreatment is to reduce the natural biomass recalcitrance and thus enhance sac- charification yield. A further prerequisite for efficient utilization of all biomass components is their efficient fractiona- tion into well-defined process streams. Currently available pretreatment methods only partially fulfill these criteria. Steam explosion, for example, excels as a pretreatment method but has limited potential for fractionation, whereas organosolv is excellent for delignification but offers poor biomass deconstruction. Results: In this article, a hybrid method combining the cooking and fractionation of conventional organosolv pre - treatment with the implementation of an explosive discharge of the cooking mixture at the end of pretreatment was developed. The effects of various pretreatment parameters (ethanol content, duration, and addition of sulfuric acid) were evaluated. Pretreatment of birch at 200 °C with 60% v/v ethanol and 1% w/w biomass H 2 SO 4 was proven to be the most efficient pretreatment condition yielding pretreated solids with 77.9% w/w cellulose, 8.9% w/w hemicellulose, and 7.0 w/w lignin content. Under these conditions, high delignification of 86.2% was demonstrated. The recovered lignin was of high purity, with cellulose and hemicellulose contents not exceeding 0.31 and 3.25% w/w, respectively, and ash to be < 0.17% w/w in all cases, making it suitable for various applications. The pretreated solids presented high saccharification yields, reaching 68% at low enzyme load (6 FPU/g) and complete saccharification at high enzyme load (22.5 FPU/g). Finally, simultaneous saccharification and fermentation (SSF) at 20% w/w solids yielded an ethanol titer of 80 g/L after 192 h, corresponding to 90% of the theoretical maximum. Conclusions: The novel hybrid method developed in this study allowed for the efficient fractionation of birch biomass and production of pretreated solids with high cellulose and low lignin contents. Moreover, the explosive dis- charge at the end of pretreatment had a positive effect on enzymatic saccharification, resulting in high hydrolyzability of the pretreated solids and elevated ethanol titers in the following high-gravity SSF. To the best of our knowledge, the ethanol concentration obtained with this method is the highest so far for birch biomass

Hydrothermal pretreatment and enzymatic hydrolysis of lignocellulosic biomass

Lignocellulosic biomass which includes agricultural and forestry residues and/or byproducts, is a promising source for the production of 2nd generation biofuels and chemicals. Lignocellulosic biomass from beech wood and pinewood, poplar and grapevine trimmings were used in the present study. The biomass samples were subjected to hydrothermal pretreatment, which aimed at the deconstruction of the microfibrils, and to enzymatic saccharification of cellulose towards glucose, while the effect of other mild processes, such as surface lignin extraction with organic solvents and the effect of a simultaneous enzymatic hydrolysis with milling, on the saccharification efficiency were also evaluated. The main effect of hydrothermal pretreatment was the selective dissolution of hemicellulose, catalyzed by the acetyl units contained in hemicellulose. Hemicellulose was retrieved in the hydrothermal process liquids as a mixture of soluble xylo-oligomers/monomeric xylose, and their concentration and ratio is governed by the severity of the processes, which is expressed with the severity factor logRo. Maximum hemicellulose recovery in the liquid product for all four types of biomass was close to 60%, a value achieved at severities of logRo= 3.8-4.14, with a corresponding value of 70-80% removal of hemicellulose from biomass. At more intense reaction conditions of logRo 4,7 almost all hemicellulose was removed from biomass but the greater part of xylose was converted to degradation products, such as furfural, formic acid and furoic acid, via dehydration, (re)hydration and oxidation reactions. Small amounts of glucose were also detected in the hydrothermal process liquids, originating either from a limited hydrolysis of cellulose or from soluble extractives present in the biomass of poplar, grapevine and pinewood, which were also converted to degradation products, such as HMF, formic and levulinic acid. Lignin is partially dissolved, relocated and recondensed on the surface of the biomass, while structural cellulose remains almost intact. Ηydrothermal pretreatment lead to an increase of the specific surface area and pore volume of the biomass. In the case of beech wood, poplar, and grapevine biomass, hydrothermal pretreatment allowed for the relatively high saccharification of cellulose at conversion levels of 67%, 50% and 75%, respectively, but only 19% for pine wood. The extraction of surface lignin with the organic solvents ethanol and acetone improved enzymatic conversion for beech wood and grapevine trimmings. Extraction of lignin with acetic acid enabled almost complete delignification of beech wood and its almost complete enzymatic saccharification. Enzymatic hydrolysis combined with milling led to additional improvement of saccharification for all types of biomass, reaching almost complete conversion for beech, 95% for grapevine, 67% for poplar and 58% for pine. The combined enzymatic hydrolysis - milling process resulted in some cases in considerable reduction of the necessary amount of enzyme without affecting the overall hydrolysis conversion. Finally the pretreated and delignified biomass samples were used as a low cost substrate for the production of cellulase from the microorganism T. reesei, achieving greater productivities compared to untreated biomass, while the beech wood hydrothermally pretreated and delignified by acetic acid gave cellulase yields similar to those obtained with commercial crystalline cellulose.Η λιγνοκυτταρινούχα βιομάζα, που περιλαμβάνει κάθε είδους αγροτικά και δασικά υπολείμματα και παραπροϊόντα, αποτελεί μια υποσχόμενη ανανεώσιμη πηγή για την παραγωγή ενέργειας, βιοκαυσίμων και χημικών ενώσεων υψηλής προστιθέμενης αξίας. Στην παρούσα διδακτορική διατριβή χρησιμοποιήθηκαν ως λιγνοκυτταρινούχα βιομάζα ξύλο οξυάς και πεύκου και κλαδέματα λεύκας και αμπελιού. Η λιγνοκυτταρινούχα βιομάζα υποβλήθηκε σε υδροθερμική προκατεργασία, για την υδρόλυση της ημικυτταρίνης, και σε ενζυμική υδρόλυση για την σακχαροποίηση της κυτταρίνης. Επιπλέον μελετήθηκε η επίδραση ήπιων διεργασιών, όπως η εκχύλιση της λιγνίνης με οργανικούς διαλύτες και η εφαρμογή άλεσης ταυτόχρονα με την ενζυμική υδρόλυση της κυτταρίνης. Η υδροθερμική προκατεργασία είχε ως αποτέλεσμα την εκλεκτική απομάκρυνση της ημικυτταρίνης μέσω όξινης υδρόλυσης με καταλύτη τις οξικές ομάδες που εμπεριέχονται στην ημικυτταρίνη. Η ημικυτταρίνη ανακτάται στα υγρά προϊόντα της υδροθερμικής προκατεργασίας ως μίγμα ολιγομερών/μονομερών ξυλόζης, ενώ ο λόγος της συγκέντρωσης τους καθορίζεται από την ένταση των πειραματικών συνθηκών εκφραζόμενη με τον συντελεστή δριμύτητας logRo. Η μέγιστη ανάκτηση ημικυτταρίνης κυμαίνεται στο 60% και για τα τέσσερα είδη βιομάζας και επιτυγχάνεται σε τιμές logRo 3,8-4,14, με απομάκρυνση της ημικυτταρίνης από τη βιομάζα 70-80%. Σε υψηλότερες τιμές logRo 4,7 επιτυγχάνεται σχεδόν πλήρης απομάκρυνση της ημικυτταρίνης απο τη βιομάζα αλλά το μεγαλύτερο ποσοστό της παραγόμενης ξυλόζης και των υπολοίπων πεντοζών μετατρέπεται σε προϊόντα αποικοδόμησης (φουρφουράλη, φορμικό οξύ και φουροϊκό οξύ). Επιπλέον, παράγονται και μικρές ποσότητες γλυκόζης μέσω περιορισμένης υδρόλυσης της κυτταρίνης ή λόγω των διαλυτών εκχυλίσιμων συστατικών της βιομάζας αμπελιού, λεύκας και πεύκου, και προϊόντα αποικοδόμησης της γλυκόζης, όπως 5-υδροξυμεθυλοφουρφουράλη (HMF), φορμικό οξύ και λεβουλινικό οξύ. Η λιγνίνη υφίσταται μερική διαλυτοποίηση, αναδιάταξη και επανασυμπύκνωση στην επιφάνεια των σωματιδίων της βιομάζας ενώ η δομική κυτταρίνη υφίσταται πολύ μικρές μεταβολές. Η υδροθερμική προκατεργασία οδηγεί σε αύξηση της ειδικής επιφάνειας και του όγκου πόρων των σωματιδίων. Για τη βιομάζα από ξύλο οξυάς, λεύκας, και αμπελιού, η υδροθερμική προκατεργασία επέτρεψε την σχετικά υψηλή ενζυμική σακχαροποίηση της κυτταρίνης σε ποσοστό 67%, 50% και 75% αντίστοιχα, ενώ αντίθετα μικρή ήταν η μετατροπή στην περίπτωση του πεύκου με 19% σακχαροποίηση. Η απομάκρυνση της επιφανειακής λιγνίνης με τη χρήση οργανικών διαλυτών αιθανόλη και ακετόνη βελτίωσε την απόδοση της ενζυμικής μετατροπής κυρίως για την οξυά και τη λεύκα. H εκχύλιση της λιγνίνης από βιομάζα οξυάς με οξικό οξύ επέτρεψε την πλήρη απολιγνινοποίηση της βιομάζας και την σχεδόν πλήρη ενζυμική σακχαροποίηση. Ο συνδυασμός της ενζυμικής υδρόλυσης με άλεση επέτρεψε την βελτίωση της σακχαροποίησης για όλες τις βιομάζες, φτάνοντας και πάλι την πλήρη σακχαροποίηση για την οξυά, στο 95% για το αμπέλι, στο 67% για τη λεύκα και στο 58% για το πεύκο. Επίσης, η συνδυασμένη ενζυμική υδρόλυση με άλεση οδήγησε σε ορισμένες περιπτώσεις στην μείωση της ποσότητας του προστιθέμενου ενζύμου χωρίς σημαντική μεταβολή στην μετατροπή της κυτταρίνης σε γλυκόζη. Τέλος τα υδροθερμικά προκατεργασμένα και απολιγνινοποιημένα δείγματα βιομάζας χρησιμοποιήθηκαν ως χαμηλού κόστους υποστρώματα για την παραγωγή κυτταρινασών από τον μύκητα T. reesei, επιτυγχάνοντας μεγαλύτερες ενεργότητες σε σχέση με την αρχική βιομάζα, ενώ η βιομάζα οξυάς που υπέστη υδροθερμική προκατεργασία και απολιγνινοποίηση με οξικό οξύ, οδήγησε σε παραγωγικότητα κυτταρινασών παρόμοια με αυτή της καθαρής εμπορικής κυτταρίνης

Organosolv Fractionation of Softwood Biomass for Biofuel and Biorefinery Applications

Softwoods represent a significant fraction of the available lignocellulosic biomass for conversion into a variety of bio-based products. Its inherent recalcitrance, however, makes its successful utilization an ongoing challenge. In the current work the research efforts for the fractionation and utilization of softwood biomass with the organosolv process are reviewed. A short introduction into the specific challenges of softwood utilization, the development of the biorefinery concept, as well as the initial efforts for the development of organosolv as a pulping method is also provided for better understanding of the related research framework. The effect of organosolv pretreatment at various conditions, in the fractionation efficiency of wood components, enzymatic hydrolysis and bioethanol production yields is then discussed. Specific attention is given in the effect of the pretreated biomass properties such as residual lignin on enzymatic hydrolysis. Finally, the valorization of organosolv lignin via the production of biofuels, chemicals, and materials is also described

Current and novel approaches to downstream processing of microalgae: A review

International audienceBiotechnological application of microalgae cultures at large scale has significant potential in the various fields of biofuels, food and feed, cosmetic, pharmaceutic, environmental remediation and water treatment. Despite this great potential application, industrialisation of microalgae culture and valorisation is still faced with serious remaining challenges in culture scale-up, harvesting and extraction of target molecules. This review presents a general summary of current techniques for harvesting and extraction of biomolecules from microalgae, their relative merits and potential for industrial application. The cell wall composition and its impact on microalgae cell disruption is discussed. Additionally, more recent progress and promising experimental methods and studies are summarised that would allow the reader to further investigate the state of the art. A final survey of energetic assessments of the different techniques is also made. Bead milling and high-pressure homogenisation seem to give clear advantages in terms of target high value compounds extraction from microalgae, with enzyme hydrolysis as a promising emerging technique. Future industrialisation of microalgae for high scale biotechnological processing will require the establishment of universal comparisonstandards that would enable easy assessment of one technique against another

Evaluation of Mediterranean Agricultural Residues as a Potential Feedstock for the Production of Biogas via Anaerobic Fermentation

Hydrothermal, dilute acid, and steam explosion pretreatment methods, were evaluated for their efficiency to improve the methane production yield of three Mediterranean agricultural lignocellulosic residues such as olive tree pruning, grapevine pruning, and almond shells. Hydrothermal and dilute acid pretreatments provided low to moderate increase in the digestibility of the biomass samples, whereas steam explosion enabled the highest methane yields to be achieved for almond shells at 232.2 ± 13.0 mL CH4/gVS and olive pruning at 315.4 ± 0.0 mL CH4/gVS. Introduction of an enzymatic prehydrolysis step moderately improved methane yields for hydrothermal and dilute acid pretreated samples but not for the steam exploded ones

Evaluation of Mediterranean Agricultural Residues as a Potential Feedstock for the Production of Biogas via Anaerobic Fermentation

Hydrothermal, dilute acid, and steam explosion pretreatment methods, were evaluated for their efficiency to improve the methane production yield of three Mediterranean agricultural lignocellulosic residues such as olive tree pruning, grapevine pruning, and almond shells. Hydrothermal and dilute acid pretreatments provided low to moderate increase in the digestibility of the biomass samples, whereas steam explosion enabled the highest methane yields to be achieved for almond shells at 232.2 ± 13.0 mL CH 4 /gVS and olive pruning at 315.4 ± 0.0 mL CH 4 /gVS. Introduction of an enzymatic prehydrolysis step moderately improved methane yields for hydrothermal and dilute acid pretreated samples but not for the steam exploded ones

Organosolv biomass pretreatment for fuel production

Never has the issue of sustainability gathered so much importance than now. The latest report by the Intergovernmental Panel on Climate Change2 necessitates us to take drastic actions to combat the emissions of greenhouse gases. A rising population, an urban lifestyle and increased economic growth would place enormous pressure on the global energy demand and food production. Thus, targeting industrial chemicals – valued at 3 trillion USD per year, with bio-based processes will enable the production of these chemicals from a non-petrochemical feedstock. Biomass is a renewable feedstock that is available abundantly. However, it needs to be processed, to release the sugars that can be utilised by microorganisms to produce various products of interest. Several pretreatment methods are currently available for biomass deconstruction, but inevitably they produce compounds, such as hydroxyl methyl furfural and furfural, that are toxic to the microorganisms. Organosolv pretreatment has shown much promise, as it yields three distinct and clean streams — cellulose, hemicellulose and lignin, that are microorganisms ‘friendly’.The cellulose stream can be hydrolysed using a cocktail of enzymes (Novozymes) to release the glucose monomers. In this study, we evaluated the sugar yields from the hydrolysis of organosolv pretreated spruce and birch biomass

Organosolv pretreatment produces an inhibitor free hydrolysate with superior fermentability at high-solids loadings

Never has the issue of sustainability garnered so much importance than now. The fifth assessment report by the Intergovernmental Panel on Climate Change necessitates us to take drastic actions to combat the emissions of greenhouse gases. A rising population, an urban lifestyle and increased economic growth would place enormous pressure on the global energy demand and food production. Thus, targeting industrial chemicals – valued at 3 trillion USD per year, with bio-based processes will enable the production of these chemicals from a non-petrochemical feedstock. Towards fulfilling some of the sustainable development goals formulated by the United Nations Biomass is a renewable feedstock that is available abundantly. However, it needs to be processed, to release the sugars that can be utilised by microorganisms to produce various products of interest. Several pretreatment methods are currently available for biomass deconstruction, but inevitably they produce compounds, such as hydroxy methyl furfural and furfural, that are toxic to the microorganisms. Organosolv (with ethanol as a solvent) pretreatment has shown much promise, as it yields three distinct and clean streams — cellulose, hemicellulose and lignin, that are less toxic to the microorganisms. The enriched cellulose fraction can be hydrolysed using a cocktail of enzymes to release the glucose monomers and subsequently be fermented to ethanol using native yeasts. In this study, we report the sugar yields during the hydrolysis of organosolv pretreated birch and spruce biomass and the superior fermentability of birch biomass over spruce, in an SSF process using Ethanol Red yeast. Ethanol yields up to 95% of theoretical maximum at 5% solids loading could be achieved in a small-scale set-up. Studies at a large-scale including LCA analysis would provide conclusive evidence on the efficacy of this pretreatment method over others

Investigation of different pretreatment methods of Mediterranean-type ecosystem agricultural residues: characterisation of pretreatment products, high-solids enzymatic hydrolysis and bioethanol production

<p>Agricultural and agro-industrial lignocellulosic residues represent an important renewable resource for the production of fuels and chemicals towards a bio-based economy. Olive pruning, vineyard pruning and almond shells are important residues from agricultural activities in Mediterranean-type ecosystems. In the current work, bioethanol production from the above three types of agro-residues was studied, focusing on the effect of different pretreatment methods on enzymatic saccharrification efficiency of cellulose and production of second-generation bioethanol. Dilute acid, hydrothermal and steam explosion pretreatments were compared in order to remove hemicellulose and facilitate the subsequent enzymatic hydrolysis of the hemicellulose-deficient biomass to glucose. Enzymatic hydrolysis was performed in a free-fall mixing reactor enabling high solids loading of 23% w/w. This allowed hydrolysis of up to 67% of available cellulose in almond shells and close to 50% in olive pruning samples, and facilitated high ethanol production in the subsequent fermentation step; the highest ethanol concentrations achieved were 47.8 g/L for almond shells after steam explosion and 42 g/L for hydrothermally pretreated olive pruning residue.</p

High-Titer Methane from Organosolv-Pretreated Spruce and Birch

The negative impact of fossil fuels and the increased demand for renewable energy sources has led to the use of novel raw material sources. Lignocellulosic biomass could serve as a possible raw material for anaerobic digestion and production of biogas. This work is aimed at using forest biomass, both softwood (spruce) and hardwood (birch), as a raw material for anaerobic digestion. We examined the effect of different operational conditions for the organosolv pretreatment (ethanol content, duration of treatment, and addition of acid catalyst) on the methane yield. In addition, we investigated the effect of addition of cellulolytic enzymes during the digestion. We found that inclusion of an acid catalyst during organosolv pretreatment improved the yields from spruce, but it did not affect the yields from birch. Shorter duration of treatment was advantageous with both materials. Methane yields from spruce were higher with lower ethanol content whereas higher ethanol content was more beneficial for birch. The highest yields obtained were 185 mL CH4/g VS from spruce and 259.9 mL CH4/g VS from birch. Addition of cellulolytic enzymes improved these yields to 266.6 mL CH4/g VS and 284.2 mL CH4/g VS, respectively.Validerad; 2017; Nivå 2; 2017-04-03 (andbra)</p