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L'étape limitante pour les applications possibles de valorisation biotechnologiques des substrats agricoles cellulosiques (pailles de céréales, pulpes de betteraves, bagasse...) est l'hydrolyse chimique ou enzymatique de la cellulose en sucres simples. Nos recherches ont été orientées vers la production de cellulases d'un champignon filamenteux cellulolytique #Trichoderma harzianum$ cultivé sur différents substrats lignocellulosiques par fermentation en milieu solide. L'étude de la physiologie de la croissance et de la sporulation de #T. harzianum$ nous a permis de définir des conditions et des milieux de culture optima pour ce microorganisme. De même l'utilisation d'un dispositif d'incubation simple nous a permis de suivre le développement de #T. harzianum$ et d'étudier au laboratoire la production de cellulases sur divers substrats lignocellulosiques (paille et son de blé, pulpe de betterave, bagasse) en milieu solide. Pour l'extrapolation des résultats au niveau pilote expérimental nous avons mis au point deux nouveaux fermenteurs pour la culture en milieu solide : un fermenteur à disques de 4,4 litres pour la production d'inoculum ; un fermenteur statique de 100 litres pour la production de cellulases. Ce travail a permis d'élaborer un nouveau procédé de production et d'extraction de cellulases de #T. harzianum$ par culture en milieu solide statique. De plus trois brevets d'invention ont été déposés à l'ANVAR. (Résumé d'auteur)

Ferulic, caffeic, p-coumaric and chlorogenic acids are classified as hydroxycinnamic acids, presenting anticarcinogenic, anti-inflammatory and antioxidant properties. In this work, enzymatic extraction has been studied in order to extract high value-added products like hydroxycinnamic acids from coffee pulp. A commercial pectinase and enzyme extract produced by Rhizomucor pusillus strain 23aIV in solid-state fermentation using olive oil or coffee pulp (CP) as an inducer of the feruloyl esterase activity were evaluated separately and mixed. The total content (covalently linked and free) of ferulic, caffeic, p-coumaric and chlorogenic acids was 5276 mg per kg of coffee pulp. Distribution was as follows (in %): chlorogenic acid 58.7, caffeic acid 37.6, ferulic acid 2.1 and p-coumaric acid 1.5. Most of the hydroxycinnamic acids were covalently bound to the cell wall (in %): p-coumaric acid 97.2, caffeic acid 94.4, chlorogenic acid 76.9 and ferulic acid 73.4. The content of covalently linked hydroxycinnamic acid was used to calculate the enzyme extraction yield. The maximum carbon dioxide rate for the solid-state fermentation using olive oil as an inducer was higher and it was reached in a short cultivation time. Nevertheless, the feruloyl esterase (FAE) activity (units per mg of protein) obtained in the fermentation using CP as an inducer was 31.8 % higher in comparison with that obtained in the fermentation using olive oil as the inducer. To our knowledge, this is the first report indicating the composition of both esterified and free ferulic, caffeic, p-coumaric and chlorogenic acids in coffee pulp. The highest yield of extraction of hydroxycinnamic acids was obtained by mixing the produced enzyme extract using coffee pulp as an inducer and a commercial pectinase. Extraction yields were as follows (in %): chlorogenic acid 54.4, ferulic acid 19.8, p-coumaric acid 7.2 and caffeic acid 2.3. An important increase in the added value of coffee pulp was mainly due to the extraction of chlorogenic acid.