Enzymatic saccharification and fermentation of rice processing residue for ethanol production at constant temperature

• Constant temperature for hydrolysis and fermentation.
• Conversion of 84% of fermentable sugar to ethanol.
• Yield of 175 g of ethanol per kg of rice bran.

The aim was to investigate the enzymatic saccharification and fermentation for ethanol production. The rice bran, inoculum, corn steep liquor, soybean bran, amylase, cellulase concentrations and time of inoculum addition were evaluated using a Plackett-Burman (PB) experimental design. Furthermore, a central composite rotational design (CCRD) for three independent variables was carried out to optimise the ethanol production. Inoculum was added after 18 h of enzymatic hydrolysis and all the process was carried out at 35 °C during 48 h. Maximum ethanol production was 175 ± 5.8 g kg−1 obtained at 15% (m/m) concentration of inoculum, 150 g l−1 of rice bran and 3% (m/m) of cellulase. Rice bran is therefore a promising raw material for ethanol production.