10-04: Diluted thermopressurized phosphoric acid as a gentle proton donor for the hydrolysis of polysaccharides from several phytobiomass models: softwood heteromannans as target

We have developed a wide scope pioneering very diluted acid pretreatment for cane/ sorghum bagasses using thermopressurized phosphoric acid (e.g., 0.0625 % and 200^oC) to depolymerize the hemicellulosic heteroxylan fraction and to render the residual cellulose fully hydrolysable by commercial cellulases ((J.D.Fontana et al. (1984) Biotechnol. Bioeng.Symp.14:175-186) besides satisfactory solubilization of lignin, too. Another advantage of this mild phosphorolysis is the use of the catalyst as one of the conutrients for any further free sugars fermentation step. Later, phosphoric technology was adapted to starch under milder kinetic conditions (e.g., 160-180^oC) to generate maltosaccharides/ glucose {J.D.Fontana. Brazilian patent PI0002001-0; J.D.Fontana et al. (2000); Appl. Biochem.Biotechnol., 91-93:469-478}. Recently we applied the same technology to inulin polyfructose to produce nutraceutical FOS-FructoOligoSaccharides {J.D.Fontana et al. Brazilian patent request PI0703206-4, 2007; J.Med.Food (2011) 14(11):1425-1430} under even milder conditions (75-85^oC)  at pHs as gentle as 2.0-2.5, again taking advantage of H₃PO₄ cogenerating much less furfural and hydroxymethylfurfural than the stronger H₂SO₄ and HCl. A new capability of the same acid catalyst to release free mono-/oligosaccharides from the complex hemicellulose fraction {(h)-(Xyl)_n/(h)-(Man)_n´} of an alternative ligno(hemi)cellulosic model, namely, the angiosperm Pinus taeda sawdust is now reported, along with cane bagasse and seed gum (h)mannans as comparison models. Extensive chromatographic analyses after phosphoric pretreatments  at pH 2.00-1.75 and 3-12 atm (144-185^oC) ranges indicated that modulation of the severity parameters allows the recovery of nutraceutical oligosaccharides as an alternative to biofuel stuffs (Funding: CAPES-CNPQ-SETI/PR).