pubs.acs.org/JAFC Published on Web 07/02/2010 © 2010 American Chemical Society J. Agric. Food Chem. 2010, 58, 8279–8285 8279 DOI:10.1021/jf101174x Miscanthus x giganteus Bark Organosolv Fractionation: Fate of Lipophilic Components and Formation of Valuable Phenolic Byproducts JUAN JOSE ´ VILLAVERDE,* ,† ALBERTO DE VEGA, ‡ PABLO LIGERO, ‡ CARMEN S. R. FREIRE, † CARLOS PASCOAL NETO, † AND ARMANDO J. D. SILVESTRE † † Centre for Research in Ceramics and Composite Materials (CICECO) and Department of Chemistry, University of Aveiro, Aveiro 3810-193, Portugal, and ‡ Department of Physical Chemistry and Chemical Engineering, University of A Corun˜ a, A Corun˜ a 15071, Spain The behavior of Miscanthus x giganteus bark lipophilic extractives during three acid organosolv pulping processes (Acetosolv, formic acid fractionation, and Milox) was investigated. It was demonstrated that nearly 90% of the lipophilic extractives were removed from pulps by either dissolution in the organosolv liquors (fatty acids and alcohols) or extensive degradation (sterols). The organosolv liquors were found to be rich in vanillin, syringaldehyde, and ferulic, vanillic, and p-coumaric acids. The Acetosolv fractionation process was found to be the most efficient in the removal of lipophilic components from pulps, and it was also the process that generated higher amounts of valuable monomeric phenolic compounds that could be exploited within the biorefinery context. KEYWORDS: Miscanthus x giganteus; organosolv fractionation; lipophilic extractives; GC-MS analysis INTRODUCTION Biomass is expected to become the major renewable resource for the production of chemicals, materials, fuels, and energy (without affecting food and feed supplies), within a future sustainable society, following the so-called biorefinery concept ( 1 -3 ). To meet that vision, i.e., to use the available biomass as effi- ciently as possible and with the lowest environmental impact, deep scientific and technological improvements will be necessary cover- ing all steps of the production chain, from agro-forest activities to the conversion of raw materials into valuable chemicals/mate- rials ( 1 -3 ). The selection of adequate plant species and of suitable processing technologies for their conversion are two crucial aspects to meet such goals. The genus Miscanthus and, particularly, the sterile hybrid horticultural genotype Miscanthus x giganteus Greef and Deuter ex Hodkinson and Renvoize ( 4 ) have attracted the interest of the European Union (EU) authorities as a promising crop for energy and materials production, because of its excellent productivity, rapid growth, and high resistance to disease ( 5 ). In the past decade, numerous studies have been carried out to access the potential of this grass in a wide range of applications ( 6 -14 ). Most of the mentioned applications require the fractionation of raw material into their main macromolecular components and were primarily based on pulping processes ( 15 -17 ). Among them, organosolv fractionation processes have demonstrated to be promising alternatives to exploit some of these biomass resources for the production of methylcellulose ( 13 ), carboxy- methylcellulose ( 6 ), adhesives ( 7 ), ethanol ( 14 ), and activated carbon ( 9 ), among other products ( 8 ). In this vein, we have studied the behavior of M. x giganteus bark during organosolv fractionation, with mixtures of acetic acid, water, and hydrochloric acid (Acetosolv process) ( 16, 17 ), with formic acid, water, and hydrochloric acid as catalysts (henceforth referred as the Formosolv process) ( 15, 17 ), and with mixtures of formic acid, water, and hydrogen peroxide (Milox process) ( 18 ). The totally chlorine-free (TCF) bleaching of the ensuing pulps ( 19 , 20) and the characterization of their main macromolecular compo- nents ( 11 , 12) were also investigated. Besides the macromolecular fractions, the exploitation of the extractives fraction could also contribute to the global valorization of the plant biomass. In this perspective, we have reported the first detailed characterization of the lipophilic extractives of M. x giganteus ( 11 ), showing that this species could be seen as a promising source of low-molecular-weight components, such as sterols and aromatic compounds. To our knowledge, the behavior of M. x giganteus lipophilic components during the pulping and bleaching processes men- tioned above has not been studied thus far; however, this knowl- edge is particularly important, on the one hand, in the perspective of their potential exploitation in an integrated biorefinery and, on the other hand, considering their potential impact in the pulping and bleaching processes. It is known that the presence of lipophilic components causes problems in the pulp industry, such as the formation of deposits in machinery and dark spots in bleached pulp, known as pitch (e.g., refs 21 -25 ), as well as some increase in chemicals consumption during pulping and bleaching ( 26 ). Furthermore, extractives and their derivatives may impact bleaching effluents toxicity (e.g., refs 27 and 28 ). However, these studies were in most cases focused on kraft pulping processes; therefore, a substantial lack of information exists when considering the behavior of these components during organosolv fractionation processes. *To whom correspondence should be addressed. Telephone: þ351- 234-370-711. Fax: þ351-234-370-084. E-mail: jjvillaverde@ua.pt.