Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Michèle Asther is active.

Publication


Featured researches published by Michèle Asther.


Journal of Applied Microbiology | 2006

Fungal tyrosinases: new prospects in molecular characteristics, bioengineering and biotechnological applications

S. Halaouli; Michèle Asther; J.-C. Sigoillot; Moktar Hamdi; A. Lomascolo

Tyrosinases are type‐3 copper proteins involved in the initial step of melanin synthesis. These enzymes catalyse both the o‐hydroxylation of monophenols and the subsequent oxidation of the resulting o‐diphenols into reactive o‐quinones, which evolve spontaneously to produce intermediates, which associate in dark brown pigments. In fungi, tyrosinases are generally associated with the formation and stability of spores, in defence and virulence mechanisms, and in browning and pigmentation. First characterized from the edible mushroom Agaricus bisporus because of undesirable enzymatic browning problems during postharvest storage, tyrosinases were found, more recently, in several other fungi with relevant insights into molecular and genetic characteristics and into reaction mechanisms, highlighting their very promising properties for biotechnological applications. The limit of these applications remains in the fact that native fungal tyrosinases are generally intracellular and produced in low quantity. This review compiles the recent data on biochemical and molecular properties of fungal tyrosinases, underlining their importance in the biotechnological use of these enzymes. Next, their most promising applications in food, pharmaceutical and environmental fields are presented and the bioengineering approaches used for the development of tyrosinase‐overproducing fungal strains are discussed.


Journal of Biotechnology | 1994

Vanillin as a product of ferulic acid biotransformation by the white-rot fungus Pycnoporus cinnabarinus I-937: identification of metabolic pathways

B. Falconnier; Catherine Lapierre; Laurence Lesage-Meessen; G. Yonnet; Pascal Brunerie; B. Colonna-Ceccaldi; Georges Corrieu; Michèle Asther

Abstract Ferulic acid metabolism was studied in cultures of the white-rot fungus Pycnoporus cinnabarinus I-937. After 6 days of growth, during the secondary metabolism of the fungus, the concentration of vanillin in the culture medium reached a maximum of 64 mg l −1 , corresponding to a molar yield of 27.5%. During the biotransformation process, the propenoic side chain of ferulic acid was oxidatively cleaved to yield vanillic acid, further decarboxylated to 2-methoxyhydroquinone. In addition, two reductive routes were evidenced, involving the conversion of ferulic and vanillic acids into coniferyl and vanillyl alcohols, respectively. The biotransformation process was not easily controlled since the P. cinnabarinus species is known to release laccase into the growth medium. When produced, the enzyme countered the vanillin formation by promoting the polymerization of ferulic acid into lignin-like polymers.


Journal of Applied Microbiology | 2005

Characterization of a new tyrosinase from Pycnoporus species with high potential for food technological applications

S. Halaouli; Mi. Asther; K. Kruus; L. Guo; M. Hamdi; J.-C. Sigoillot; Michèle Asther; A. Lomascolo

Aims:  Tyrosinase production by Pycnoporus cinnabarinus and Pycnoporus sanguineus was screened among 20 strains originating from various geographical areas, particularly from tropical environments. The tyrosinase from the most efficient strain was purified and characterized and tested for food additive applications.


Fungal Genetics and Biology | 2008

FOLy: An integrated database for the classification and functional annotation of fungal oxidoreductases potentially involved in the degradation of lignin and related aromatic compounds

Anthony Levasseur; François Piumi; Pedro M. Coutinho; Corinne Rancurel; Michèle Asther; Michel Delattre; Bernard Henrissat; Pierre Pontarotti; Marcel Asther; Eric Record

The breakdown of lignin by fungi is a key step during carbon recycling in terrestrial ecosystems. This process is of great interest for green and white biotechnological applications. Given the importance of these enzymatic processes, we have classified the enzymes potentially involved in lignin catabolism into sequence-based families and integrated them in a newly developed database, designated Fungal Oxidative Lignin enzymes (FOLy). Families were defined after sequence similarity searches starting from protein sequences and validated by the convergence of results with biochemical experiments reported in the literature. The resulting database was applied as a tool for the functional annotation of genomes from different fungi, namely (i) the Basidiomycota Coprinopsis cinerea, Phanerochaete chrysosporium and Ustilago maydis and (ii) the Ascomycota Aspergillus nidulans and Trichoderma reesei. Genomic comparison of the oxidoreductases of these fungi revealed significant differences in the putative enzyme arsenals. Two Ascomycota fungal genomes were annotated and new candidate genes were identified that could be useful for lignin degradation and (or) melanin synthesis, and their function investigated experimentally. This database efforts aims at providing the means to get new insights for the understanding and biotechnological exploitation of the lignin degradation. A WWW server giving access to the routinely updated FOLy classifications of enzymes potentially involved in lignin degradation can be found at http://foly.esil.univ-mrs.fr.


Process Biochemistry | 2002

Feruloyl esterase from Aspergillus niger a comparison of the production in solid state and submerged fermentation

Michèle Asther; Mireille Haon; Sevastianos Roussos; Eric Record; Michel Delattre; Laurence Lesage-Meessen; Marc Labat; Marcel Asther

Solid state fermentation (SSF) culture conditions were investigated for the production of feruloyl esterase by Aspergillus niger I-1472 and compared with submerged culture conditions. Sugar beet pulp was tested for its ability to be used both as solid support and/or carbon substrate. Mycelial growth was monitored through ergosterol measurements. Under submerged culture conditions, A. niger I-1472 produced esterase active on methyl ester of cinnamic acids, principally methyl ferulate and methyl sinapinate. Under SSF culture conditions, the enzymic profile was different since significant esterase activities using methyl caffeate and methyl p-coumarate as substrate were detected, showing the presence of at least two different proteins. Northern blot analysis of the mycelium clearly indicated the expression of feruloyl esterase gene in both conditions.


Applied Biochemistry and Biotechnology | 2002

A biotechnological process involving filamentous fungi to produce natural crystalline vanillin from maize bran

Laurence Lesage-Meessen; Anne Lomascolo; Estelle Bonnin; Jean-François Thibault; Alain Buléon; Marc Roller; Michèle Asther; Eric Record; Benoit Colonna Ceccaldi; Marcel Asther

A new process involving the filamentous fungi Aspergillus niger and Pycnoporus cinnabarinus has been designed for the release of ferulic acid by enzymic degradation of a cheap and natural agricultural byproduct (autoclaved maize bran) and its biotransformation into vanillic acid and/or vanillin with a limited number of steps. On the one hand, the potentialities of A. niger I-1472 to produce high levels of polysaccharide-degrading enzymes including feruloyl esterases and to transform ferulic acid into vanillic acid were successfully combined for the release of free ferulic acid from autoclaved maize bran. Then vanillic acid was recovered and efficiently transformed into vanillin by P. cinnabarinus MUCL 39533, since 767 mg/L of biotechnologic vanillin could be produced in the presence of cellobiose and XAD-2 resin. On the other hand, 3-d-old high-density cultures of P. cinnabarinus MUCL39533 could be fed with the autoclaved fraction of maize bran as a ferulic acid source and a. niger I-1472 culture filtrate as an extracellular enzyme source. Under these conditions, P. cinnabarinus MUCL39533 was shown to directly biotransform free ferulic acid released from the autoclaved maize bran by A. niger I-1472 enzymes into 584 mg/L of vanillin. These processes, involving physical, enzymic, and fungal treatments, permitted us to produce crystallin vanillin from autoclaved maize bran without any purification step.


BMC Evolutionary Biology | 2006

Tracking the connection between evolutionary and functional shifts using the fungal lipase/feruloyl esterase A family

Anthony Levasseur; Philippe Gouret; Laurence Lesage-Meessen; Michèle Asther; Marcel Asther; Eric Record; Pierre Pontarotti

BackgroundThere have been many claims of adaptive molecular evolution, but what role does positive selection play in functional divergence? The aim of this study was to test the relationship between evolutionary and functional shifts with special emphasis on the role of the environment. For this purpose, we studied the fungal lipase/feruloyl esterase A family, whose functional diversification makes it a very promising candidate.ResultsThe results suggested functional shift following a duplication event where neofunctionalisation of feruloyl esterase A had occurred with conservation of the ancestral lipase function. Evolutionary shift was detected using the branch-site model for testing positive selection on individual codons along specific lineages. Positively selected amino acids were detected. Furthermore, biological data obtained from site-directed mutagenesis experiments clearly demonstrated that certain amino acids under positive selection were involved in the functional shift. We reassessed evolutionary history in terms of environmental response, and hypothesized that environmental changes such as colonisation by terrestrial plants might have driven adaptation by functional diversification in Euascomycetes (Aspergilli), thus conferring a selective advantage on this group.ConclusionThe results reported here illustrate a rare example of connection between fundamental events in molecular evolution. We demonstrated an unequivocal connection between evolutionary and functional shifts, which led us to conclude that these events were probably linked to environmental change.


Journal of Applied Microbiology | 2009

High redox potential laccases from the ligninolytic fungi Pycnoporus coccineus and Pycnoporus sanguineus suitable for white biotechnology: from gene cloning to enzyme characterization and applications

Eva Uzan; P. Nousiainen; V. Balland; J. Sipila; François Piumi; David Navarro; Michèle Asther; Eric Record; A. Lomascolo

Aims:  Exploitation of natural biodiversity in species Pycnoporus coccineus and Pycnoporus sanguineus to screen for a new generation of laccases with properties suitable for the lignin‐processing sector.


Applied Microbiology and Biotechnology | 1999

Improvement of ferulic acid bioconversion into vanillin by use of high-density cultures of Pycnoporus cinnabarinus

J. Oddou; Christelle Stentelaire; Laurence Lesage-Meessen; Michèle Asther; B. Colonna Ceccaldi

Abstract High-density cultures of Pycnoporus cinnabarinus were tested with a view to optimisation of ferulic acid bioconversion into vanillin. The dry weight was increased fourfold by using glucose, fructose or a mixture of glucose and phospholipids as carbon source instead of maltose, the carbon source previously used. 5 mmol l−1 vanillin, i.e. 760 mg l−1, was produced over 15 days with glucose-phospholipid medium. In contrast, formation of vanillin was lower using glucose or fructose compared to the maltose control. A bioreactor (2 l) with a glucose-phospholipid medium gave a molar yield of vanillin of 61% (4 mmol l−1). An alternative strategy was to grow the fungus on a glucose or fructose medium for 3 days, then switch to maltose during the bioconversion phase: this method allowed 3.3 mmol l−1 vanillin to be obtained in 10 days. Many by-products such as methoxyhydroquinone and vanillyl alcohol were also produced.


Applied Microbiology and Biotechnology | 1997

An attempt to channel the transformation of vanillic acid into vanillin by controlling methoxyhydroquinone formation in Pycnoporus cinnabarinus with cellobiose

Laurence Lesage-Meessen; Mireille Haon; Michel Delattre; Jean-François Thibault; B. Colonna Ceccaldi; Michèle Asther

Abstract The effects of adding cellobiose on the transformation of vanillic acid to vanillin by two strains of Pycnoporus cinnabarinus MUCL39532 and MUCL38467 were studied. When maltose was used as the carbon source in the culture medium, very high levels of methoxyhydroquinone were formed from vanillic acid. When cellobiose was used as the carbon source and/or added to the culture medium of P. cinnabarinus strains on day 3 just before vanillic acid was added, it channelled the vanillic acid metabolism via the reductive route leading to vanillin. Adding 3.5 g l−1 cellobiose to 3-day-old maltose cultures of P. cinnabarinus MUCL39532 and 2.5 g l−1 cellobiose to 3-day-old cellobiose cultures of P. cinnabarinus MUCL38467, yielded 510 mg l−1 and 560 mg l−1 vanillin with a molar yield of 50.2 % and 51.7 % respectively. Cellobiose may either have acted as an easily metabolizable carbon source, required for the reductive pathway to occur, or as an inducer of cellobiose:quinone oxidoreductase, which is known to inhibit vanillic acid decarboxylation.

Collaboration


Dive into the Michèle Asther's collaboration.

Top Co-Authors

Avatar

Eric Record

Aix-Marseille University

View shared research outputs
Top Co-Authors

Avatar

Marcel Asther

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

Laurence Lesage-Meessen

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

David Navarro

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

Jean-Claude Sigoillot

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

Anne Lomascolo

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

Mireille Haon

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar

Michel Delattre

Institut national de la recherche agronomique

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Christelle Stentelaire

Institut national de la recherche agronomique

View shared research outputs
Researchain Logo
Decentralizing Knowledge