Composition analyses of pretreated samples were performed
after separating pretreated liquid and solid by centrifugation.
Monomeric sugars and inhibitor concentrations in the pretreatment
liquor were analyzed directly by HPLC (Aminex HPX-87H,
Bio-Rad, Hercules, CA). To measure oligomeric sugars in the pretreatment
liquor, liquor was adjusted to a final concentration of
4% acid by adding 72% sulfuric acid. Prepared supernatant samples
were autoclaved at 121 C for 1 h as described in the NREL protocol,
‘‘Determination of sugars, byproducts and degradation products
in liquid fraction process samples (NREL/TP-510-42623).”
Samples were neutralized with barium carbonate to pH 5–6 and
total sugar concentrations were measured by HPLC (Aminex
HPX-87P). To obtain oligomeric sugar concentrations, monomeric
sugar concentrations were subtracted from the measured total
sugar concentrations.