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Banking on filamentous fungi to produce the biofuels of tomorrow
(23/03/2006)
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INRA, culture of Pycnoporus cinnabarinus |
Dwindling reserves of fossil fuel, rising oil prices and increasing quantities of greenhouse gases are just some of the reasons behind the development of biofuels. However, the present production of biofuels from rapeseed (biodiesel), wheat and beets (EBTE) is only viable on the short term: too much land would be necessary to satisfy future demands. The biofuels of tomorrow must use more abundant resources and those that are not in competition with the human food supply such as grain straw residue, wood and green urban waste. The major component of these products is lignocellulose that we do not yet know how to profitably transform into ethanol biofuel. Researchers at INRA in Marseille are studying the transformation of these lignocelluloses using enzymes from filamentous fungi in order to resolve the scientific and technological difficulties standing in the way of the development of bioethanol production in the future.
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Ethanol biofuel satisfies both economic and environmental criteria
Bioethanol makes it possible to reduce greenhouse gas emissions and particularly CO2 by 60 to 80% in comparison to petrol emissions. European directives are aiming at a 5.75% addition of biofuel (ethanol or ethanol transformed into ETBE) in lead-free petrol by 2010. In order to produce the quantities required to achieve this goal, it will be necessary to diversify the raw plant materials used.
Scientific and technological difficulties facing bioethanol production
Lignocellulose is the most abundant raw plant material on Earth. At the chemical level, celluloses are networks of chains (polymers) made up of basic units: sugars. They are bound to lignins, heteropolymers of phenolic compounds. To transform cellulose into ethanol, it must first be separated from the lignin. The following stage consists of transforming it into sugars through hydrolysis that breaks up the chains into basic units. The sugars thus obtained are then transformed into alcohol through fermentation.
Fungus enzymes are used to hydrolyse cellulose. For example, wheat straw is first prefractionated with acid. The fungus enzymes then transform the straw into sugar. The difficulty with this transformation lies in the use of enzymes that can effectively break down the lignin. This biological pathway makes it possible to carry out a highly specific action without creating any by-products. However, the cost of the bioethanol produced from the transformation of lignocellulose is very high. The challenge facing research today is therefore to improve the transformation process and reduce its cost: the biodiversity of fungi and of their enzymes provides the key to making this possible.
Yeast fermentation is generally used to convert sugars into alcohol. However, the role of pentoses, sugars formed from five carbon atoms, is not sufficiently developed at this time, creating yet another research priority.
From the genomic modelling of filamentous fungus to engine testing: NILE, the integrated European project
NILE (New Improvements for Ligno-cellulosic Ethanol), the integrated European project coordinated by the Institut Français du Pétrole (French Petroleum Institute), brings together 12 European countries and five research centres, six universities and eight industrial partners with complementary experience and know-how, covering the entire chain of bioethanol production and utilisation, all the way to automobile manufacturers. With an overall budget of 12.8 million euros, it will make it possible to develop, study and assess new technologies in view of the effective transformation of lignocellulose into bioethanol through fungal hydrolysis and fermentation. These technologies will be validated in a single and totally integrated pilot plant in order to obtain reliable data to be used for overall socio-economic and environmental evaluations and for the design of a future demonstration unit.
INRA heads the sub-project that deals with enzymatic hydrolysis, with the major goal of reducing the costs of this transformation. Within this framework, the Joint Research Unit for Biotechnology of Filamentous Fungi (INRA-Universities of Aix-Marseille I and II) in Marseille, coordinates three approaches:
- functional high-speed screening of genetic resources from the Centre Français des Ressources Fongiques (French Centre of Fungal Resources) of the Joint Research Unit, and the improvement of targeted fungal enzymes through directed evolution;
- genomic modelling of Trichoderma reesei through the incorporation of additional enzymes from Basidiomycetes fungi, as well as the construction of nanosomes (pluri-enzymatic complexes) and chimeric enzymes (that combine the properties of several enzymes);
- control and management of high fungal density bioreactors linked to the study of secretomes of selected fungus lines.
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Written by :
Communications Department
Contacts :
Marcel Asther, marcel.asther@esil.univ-mrs.fr
Unit :
Biotechnology of Filamentous Fungi (INRA-Universities of Aix-Marseille I and II), Avignon Research Centre, http://compact.jouy.inra.fr/compact/CONSULTER/INTER/ externe/unites/ecrans/1163
Department :
Science and Process Engineering of Agricultural Products, http://compact.jouy.inra.fr/compact/ CONSULTER/INTER/external/departements/ecrans/52
Label for the news :
Research example
Date of creation : 05/05/2006
Date of last update : 05/05/2006
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