Optimization conditions for oxalic acid pretreatment of deacetylated yellow poplar for ethanol production

The optimal conditions for pretreatment of deacetylated yellow poplar (Liriodendron tulipifera L.) with oxalic acid for ethanol production were evaluated. Yellow poplar was deacetylated by treatment with 0.8% NaOH for 80min at 60°C. The conditions for pretreatment of deacetylated yellow poplar for ethanol production via simultaneous saccharification and fermentation (SSF) were optimized using response surface methodology (RSM). All pretreatments were conducted using the same solid-to-liquid ratio (1:8) and reaction temperature (150°C). The combined severity factor (CSF) was used to determine the overall effect of pretreatment on ethanol production. Severe pretreatment conditions (long reaction time and high oxalic acid concentration) caused a decrease in the xylan content of deacetylated yellow poplar. The highest ethanol concentration obtained via SSF was 26.60g/L at CSF 1.95. Based on the RSM data, the optimal pretreatment conditions for SSF were as follows: reaction temperature, 150°C; reaction time, 45min; and oxalic acid concentration, 0.15M. Under these conditions, the highest degradation ratio was 33.72%, which implied that maximum dissolution of the chemical components of biomass occurred during pretreatment. The ethanol yield from the hydrolysate ranged from 0.29g/g to 0.49g/g. The highest ethanol concentration in the hydrolysate was obtained when pretreatment was carried out at 150°C for 30min with 0.1M oxalic acid.