Analytical methods
The total sugar content was evaluated by the phenol–sulfuric
method (Dubois et al., 1956) in previously filtered samples (Acrodisc
GHP filters (Pall Life Sciences) (13 mm £ diameter and
0.45 lm porosity for acid samples and cellulose acetate (13 mm
£ and 0.45 lm porosity) (Sartorius GmbH) for the remaining).
The identification and quantification of the monosaccharide’s
sugars were done by HPLC, in a Merck Hitachi (Darmstadt, Germany)
system, in a Aminex HPX-87H column and with a refraction
index detector. The column’s temperature was set to 50 C. The
volume of the injection was 20 lL. The eluent consisted of a previously
filtered and degasified solution of sulfuric acid 5 mM at a
flow of 0.5 mL min1. The identification and quantification of sugars’
degradation products were performed under the same conditions
used for the quantification of sugars but it was used a UV
detector instead.