African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12278

Full Length Research Paper

Investigating the potential of Aucoumea klaineana Pierre sapwood and heartwood wastes to produce cellulosic ethanol

Rodrigue Safou-Tchiama
  • Rodrigue Safou-Tchiama
  • Laboratoire de Recherche et de Valorisation du Matériau Bois (LaReVa Bois). Bât du Master Recherche en Sciences du Bois. Ecole Nationale des Eaux et Forêts. BP 3930, Libreville, Gabon.
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Sébastien Ngwa Obame
  • Sébastien Ngwa Obame
  • Laboratoire de Recherche et de Valorisation du Matériau Bois (LaReVa Bois). Bât du Master Recherche en Sciences du Bois. Ecole Nationale des Eaux et Forêts. BP 3930, Libreville, Gabon.
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Nicolas Brosse
  • Nicolas Brosse
  • Laboratoire d’Etudes et de Recherche sur le Matériau Bois, Faculté des Sciences et Techniques, Nancy-Université, Vandœuvre-lès-Nancy, France.
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Patrice Soulounganga
  • Patrice Soulounganga
  • Laboratoire Pluridisciplinaire des Sciences. Ecole Normale Supérieure. BP 17009, Libreville, Gabon.
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Timoléon Andzi Barhé
  • Timoléon Andzi Barhé
  • Laboratoire des Substances Naturelles et de Synthèse Organométalliques. Unité de Recherche en Chimie. Université des Sciences et Techniques de Masuku. BP. 941 Franceville, Gabon.
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  •  Received: 07 June 2016
  •  Accepted: 24 October 2016
  •  Published: 16 November 2016

Abstract

This work investigates for the first time the different reactivity exhibited by sapwood and heartwood wastes under two conditions: They were pretreated with catalyzed ethanol organosolv in the presence of sulfuric acid and their pulps underwent enzymatic hydrolysis by Trichoderma reesei which causes them to release neutral sugars for the production of cellulosic ethanol.  Aucoumea klaineana Pierre (Okoumé) wood wastes were used for the experiment. Organosolv pretreatment was performed to investigate how to harness the benefits of fermentable sugars and lignin, which were reacted at varying defined severity levels as follows: 160°C≤T≤210°C and 0%≤[H2SO4]≤2% (w/w). The highest ethanol organosolv lignin content was obtained at T=160°C and [H2SO4]=1% for sapwood (18.10%) and heartwood (19.46%) (w/w). Enzymatic hydrolysis of the pretreated wood samples displayed that sapwood and heartwood pulps released their highest sugars content under free acid pretreatment conditions. The maximum neutral sugar released by heartwood pulps pretreated at T=160°C and [H2SO4]=0% was 0.126 g/L while that from sapwood pretreated at T=185°C and [H2SO4]=0% was 0.125 g/L. It is noteworthy that, the neutral sugars from sapwood and heartwood do not have the same sensitivity to temperature increase. When pretreated at T=160°C and [H2SO4]=0%, sapwood pulps yielded the following neutral sugars: Xyl< Ara»Gal < Man < Glu, while heartwood was: Ara < Gal < Xyl < Man < Glu. However, with increased temperature ( T=185°C and [H2SO4]=0%), sapwood yielded the following neutral sugars: Ara < Gal < Xyl < Man < Glu, while heartwood yielded the following: Xyl < Ara»Gal < Man < Glu. Similar trend was observed in both sapwood and heartwood pulps when sulfuric acid concentration was increased.

Key words: Aucoumea klaineana Pierre, wood wastes, ethanol organosolv lignin, enzymatic hydrolysis, bioethanol.