Fig. 5
TFA hydrolysis of swollen and gelatinized cellulose generated by TFA. Cellulose samples were swollen in TFA at − 20 °C for 15 h and heated to 55 °C for up to 5 h before addition of four volumes of ethanol and washing in water. a 5 mg samples of freeze-dried (FD) and 0.5-mL suspensions of never-dried (ND) swollen and gelatinized cellulose were brought to 2-M TFA and heated to 120 °C for 90 min. Equivalent samples were hydrolyzed in acetic–nitric (A/N) reagent [38]. Control samples in TFA were diluted to 2 M with water and hydrolyzed at 120 °C (TFA direct). Additional controls were hydrolyzed with either 2 M TFA or A/N reagent. After hydrolysis, samples were centrifuged to pellet residual cellulose, and the TFA solutions dried under N2. Glucose equivalents were determined by a phenol–sulfuric assay [47, 57] in both TFA-soluble and insoluble fractions. Values represent mean and variance or S.D. of two to four samples. b Solubilized sugars from 2-M TFA hydrolysis at 120 °C were dried under a stream of nitrogen gas, and converted to alditol acetates for characterization by GC–MS [38, 55]. Values represent the means of two to four samples, with variance or S.D. within the width of the symbols