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Enhanced direct fermentative production of chemicals from forestry residues in a membrane biofilm reactor by enzymatic in-situ lignin modification

Applicant Studer Michael Hans-Peter
Number 136712
Funding scheme NRP 66 Resource Wood
Research institution Berner Fachhochschule
Institution of higher education Berne University of Applied Sciences - BFH
Main discipline Other disciplines of Engineering Sciences
Start/End 01.08.2012 - 31.01.2016
Approved amount 562'026.00
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All Disciplines (5)

Discipline
Other disciplines of Engineering Sciences
Forest Engineering
Mechanical Engineering
Chemical Engineering
Experimental Microbiology

Keywords (6)

lignin modifying enzymes; process integration; enzymatic hydrolysis; biofilm; fermentation; lignocellulosic biomass

Lay Summary (German)

Lead
Einstufige Fermentation von Holz zu Ethanol in einem Membran-Biofilm-Reaktor Im Mittelpunkt des Projekts stehen Verfahrensverbesse¬rungen zur Produktion von Bioethanol aus Holz, welches als Alternative zu fossilen Treibstoffen nur sehr geringe Mengen des klimaschädlichen CO2 emittiert. Mit Hilfe eines speziellen Reaktors und geeigneter Mikroorganismen sollen mehrere bis anhin getrennte Verfahrensschritte vereint und die Gewinnung von Ethanol aus Holz vereinfacht werden.
Lay summary

Hintergrund
Der Einsatz von Bioethanol als Treibstoff reduziert den Ausstoss von Treibhausgasen wie CO2. Bis heute wird Bioethanol meist aus Zuckerrohr oder Maisstärke hergestellt und steht somit in Konkurrenz zur Nahrungs- und Futtermittelproduktion. Ethanol kann aber auch – obgleich technisch schwieriger – aus Lignocellulose wie Holz gewonnen werden. Im derzeitigen biotechnologischen Verfahren wird die Biomasse zunächst thermochemisch vorbehandelt. Im nächsten Schritt spalten Enzyme die Cellulose zu Einfachzuckern, welche Mikroorganismen zu Ethanol vergären. Für eine kommerzielle Nutzung ist es allerdings notwendig, diesen Prozess stark zu vereinfachen und kostengünstiger zu machen.

Ziel
Die Forschungsarbeiten bauen auf ein vereinfachtes, integriertes Verfahren zur Gewinnung von Ethanol aus vorbehandelter Lignocellulose auf. In einem Multispezies-Biofilm-Membran-Reaktor (MBM-Reaktor) werden die notwendigen Enzyme hergestellt, die Hemicellulose und die Cellulose verzuckert, die resultierenden Einfachzucker fermentiert und das Ethanol schliesslich abgetrennt. Ligninreiches Holz lässt sich biotechnologisch jedoch schlecht in Ethanol umwandeln. Deswegen erweitern die Forschenden das eingesetzte mikrobielle Konsortium mit Lignin abbauenden Pilzstämmen und untersuchen, ob sich dadurch Ausbeute und Reaktionsrate verbessern und der Energieverbrauch im Vorbehandlungsschritt reduzieren lässt.

Bedeutung
Klimapolitische und ressourcenökonomische Gründe sprechen dafür, den Anteil an erneuerbaren, aus Lignocellulose hergestellten Treibstoffen zu erhöhen. Das technisch einfache MBM-Verfahren hat das Potential, Ethanol nachhaltig, effizient und auch dezentral in einem forst- oder landwirtschaftlichen Umfeld zu produzieren, wobei die Transportwege für die benötigte Biomasse kurz blieben.

Direct link to Lay Summary Last update: 29.01.2013

Lay Summary (French)

Lead
Fermentation directe du bois en éthanol dans un réacteur à biofilm sur membrane Le projet est axé sur des améliorations des procédés de production de bioéthanol à partir de bois, une alternative aux carburants fossiles ne générant que de très faibles émissions de CO2 nocives pour l’environnement. A l’aide d’un réacteur et de microorganismes adaptés, les chercheurs vont regrouper plusieurs étapes de procédés pour simplifier l’extraction d’éthanol à partir du bois.
Lay summary

Contexte
Le recours au bioéthanol en tant que carburant réduit les émissions de gaz à effet de serre tels que le CO2. A l’heure actuelle, le bioéthanol provient principalement du sucre de canne ou de l’amidon de maïs, ce qui le place en concurrence avec la production alimentaire et fourragère. Or, l'éthanol peut aussi être tiré de la lignocellulose du bois, quoi que cette extraction soit plus complexe sur le plan technique. Le procédé biotechnologique actuellement employé consiste tout d’abord à soumettre la biomasse à un prétraitement thermochimique. Des enzymes décomposent ensuite la cellulose en sucres simples, qui entrent alors en fermentation sous l’action de microorganismes pour produire de l’éthanol. Avant d’envisager une application commerciale, ce processus doit être fortement simplifié et son coût rationalisé.

But
Les travaux de recherche reposent sur un procédé intégré simplifié d’extraction d’éthanol à base de lignocellulose prétraitée. Un réacteur à biofilm sur membrane multi-espèces fabrique les enzymes nécessaires, transforme en sucres les hémicelluloses et la cellulose, engendre la fermentation des monosaccharides qui en résultent avant de séparer l'éthanol. La transformation en éthanol d’un bois riche en lignine est cependant difficile sur le plan biotechnologique. C’est pourquoi les chercheurs élargissent le consortium microbien utilisé en y ajoutant des souches de champignons dégradeurs de lignine. Ils examinent ensuite si ceci entraîne une amélioration des taux d’exploitation et de réaction et une réduction de la consommation énergétique dans l’étape de prétraitement.

Portée
Les politiques de protection du climat et de préservation des ressources plaident la cause d’un accroissement des carburants d’origine lignocellulosique. Très simple sur le plan technique, le procédé MBM a le potentiel de produire de l’éthanol de manière durable, efficiente et décentralisée, dans un environnement sylvicole ou agricole, en réduisant les trajets dus au transport de la biomasse.

Direct link to Lay Summary Last update: 29.01.2013

Lay Summary (English)

Lead
One-stage fermentation of wood into ethanol in a membrane biofilm reactor This project focuses on procedural improvements for the production of bio-ethanol from wood, which serves as an alternative to fossil fuels and emits only very small amounts of the environmentally harmful CO2. With the help of a special reactor and suitable microorganisms, several process steps that were separate until now will be integrated and the production of ethanol out of wood simplified.
Lay summary

Background
The use of bio-ethanol as fuel reduces the emission of greenhouse gases such as CO2. Bio-ethanol has so far mainly been produced from sugar cane and corn starch and has therefore competed with the production of food and fodder. Although difficult in technical terms, ethanol can also be produced from lignocellulose, e.g. wood. In the current biotechnological procedure, the biomass is initially thermochemically treated. In the next step, the enzymes split the cellulose into monosaccharides, which is then fermented into ethanol by microorganisms. This process needs to be strongly simplified and made more cost-efficient, however, before it can be used commercially.

Aim
The research work focuses on a simplified, integrated process for producing ethanol from pre-treated lignocellulose. In a multi-species biofilm membrane reactor (MBM reactor), the enzymes are produced, the hemicelluloses and cellulose saccharified, the resultant monosaccharides fermented and the ethanol ultimately separated. It is, however, difficult to transform lignin-rich wood into ethanol biotechnologically. For this reason, the researchers are expanding the microbial consortium used with lignin-degrading fungi strains to see whether the yield and reaction rate can thereby be improved and the energy consumption at the pre-treatment stage reduced.

Significance
Climate policy and resource economy offer good reasons for increasing the share of renewable fuels made from lignocellulose. The simple MBM procedure has the potential to produce ethanol sustainably, efficiently and decentrally in a forested or agricultural environment with short transport routes for the required biomass.

Direct link to Lay Summary Last update: 29.01.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Biochemical Conversion Processes of Lignocellulosic Biomass to Fuels and Chemicals – A Review
Brethauer Simone, Studer Michael (2015), Biochemical Conversion Processes of Lignocellulosic Biomass to Fuels and Chemicals – A Review, in Chimia, 69(10), 572-581.
Lignin repolymerisation in spruce autohydrolysis pretreatment increases cellulase deactivation
Pielhop Thomas, Larrazabal Gaston O., Studer Michael H., Brethauer Simone, Seidel Christoph-M., Rudolf von Rohr Philipp (2015), Lignin repolymerisation in spruce autohydrolysis pretreatment increases cellulase deactivation, in GREEN CHEMISTRY, 17(6), 3521-3532.

Collaboration

Group / person Country
Types of collaboration
Prof. Ph. Rudolf von Rohr, Inst. für Verfahrenstechnik, ETH Zürich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Werner Teufel, IAP, Graz Austria (Europe)
- Industry/business/other use-inspired collaboration

Abstract

Lignocellulosic biomass is the only sustainable resource in terms of cost, availability and scale, that can be converted into commodity chemicals or liquid fuels to reduce the world’s dependency on fossil resources such as oil. However, to unlock the potential of lignocellulosic feedstocks, their inherent recalcitrance to the release of fermentable sugars such as glucose at high yields and low costs has to be overcome. The biotechnological conversion route from the raw biomass to the desired product typically consists of three main steps: 1) a thermochemical pretreatment, 2) the production of fermentable sugars by enzymatic hydrolysis of cellulose and 3) the fermentation of the sugars to the desired product. Overall, the complexity of the process results in high capital and processing costs and it is therefore highly desirable to simplify the process scheme. In our laboratory, we have developed an innovative process, which allows the integrated production of cellulolytic enzymes, the hydrolysis of the cellulosic biomass and the fermentation of the resulting sugars to ethanol (our model substance) in a single multispecies biofilm membrane reactor. The feasibility of the concept could successfully be demonstrated by producing ethanol with >80% yield by the combined action of Trichoderma reesei and Saccharomyces cerevisiae using pure cellulose as the sole carbon source.In the herein presented project we aim to further develop our process for hardwood residues as feedstock. Wood is more recalcitrant to sugar release than herbaceous biomass especially due to its higher lignin content. Lignin protects the carbohydrate fraction and hinders the cellulolytic enzymes to reach and attack the cellulose fibres. Harsher pretreatment conditions are generally employed to overcome the higher recalcitrance, leading however to an increased consumption of energy and chemicals and to a higher formation of toxic enzyme and fermentation inhibitors. Alternatively, we propose to make use of the natural ability of fungi such as Pleurotus, Phanerochaete or Trametes to degrade or modify hindering lignin and thereby enabling more efficient saccharification of wood at milder pretreatment conditions. Furthermore, the enzymes expressed by these strains contribute to the detoxification of the pretreatment liquor. Instead of using these strains in a separate upstream biological pretreatment step as known from literature, we will incorporate them into the microbial consortium of the above described biofilm membrane reactor. Thereby, the otherwise observed loss of hemicellulose and to a lesser extent cellulose can be circumvented and the biological delignification is accelerated.
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