Sugarcane straw
The sugarcane straw was kindly provided by Usina Santa
Adélia, Jaboticabal, São Paulo, Brazil. It was collected directly
in the form left in the field after the harvest. The straw was
dried until moisture content was 11.25%. The biomass in nature
was chemically characterized for cellulose, hemicellulose and
lignin contents, according to the methodology proposed by
Gouveia and colleagues.23
Preparation of hemicellulosic hydrolyzate
The sugarcane straw was subjected to dilute-acid hydrolysis
with 1.0% (w/v) H2SO4 in a 35-L steel reactor at 121 ◦Cfor 20min
at a 1:10 solid/liquid ratio. The hemicellulosic hydrolyzate
was filtered and vacuum-concentrated at 70 ◦C to increase
the initial concentration of xylose by threefold.24 Next, it was
subjected to a detoxification treatment consisting of a pH
adjustment to 7.0 with CaO (commercial grade) and to 2.5
with H3PO4, followed by the addition of 1.0% (w/v) activated
charcoal (refined powder) and incubation at 60 ◦C, 100 rpm
for 30min.25 All the precipitates formed during the process
were removed by vacuum filtration. The treated hemicellulosic
hydrolyzate was autoclaved at 111 ◦C, for 15min to be
used as a fermentation medium.