Plant cell wall fragments released on solubilisation in trifluoroacetic acid

A scheme is presented for the fractionation of plant cell walls and treated plant cell walls (fibres) after suspending/dissolving in >99% trifluoroacetic acid (TFA), with oat straw and crystalline cellulose being given as examples. While cleavage of covalent bonds occurs, particularly in the non-cellulosic polysaccharides, many bonds are not hydrolysed and fragments have been identified in which covalent bonds remain between carbohydrates and phenolic components. Cellulose chains do not undergo extensive hydrolysis, even after being dissolved in TFA for at least 8 days. However, CP/MAS NMR and DRIFT IR spectroscopy both confirm that the secondary and tertiary structures of regenerated cellulose are severely modified. By analogy with the crystalline cellulose sample, all the cellulose from the oat straw should be present in the material which is soluble in TFA but is precipitated on addition of water (fraction II). The DRIFT spectrum of oat straw fraction II confirms the presence of non-cellulosic components as well. Most of the lignin from the straw is present in the fraction not soluble in TFA.