Deacetylation Followed by Fractionation of Yellow Poplar Sawdust for the Production of Toxicity-Reduced Hemicellulosic Sugar for Ethanol Fermentation

In order to produce bioethanol from yellow poplar sawdust without detoxification, deacetylation (mild alkali treatment) was performed with aqueous ammonia solution. To select the optimal conditions, deacetylation process was carried out using different conditions: NH₄OH loading (2–10% (w/v)) and solid-to-liquid ratio (1:4–10) at 121 °C for 60 min. In order to assess the effectiveness of deacetylation, fractionation of deacetylated yellow poplar sawdust was performed using dilute acid (H₂SO₄, 0.5–2.0% (w/v)), reaction temperature (130–150 °C) and time (10–80 min). The toxicity-reduced hemicellulosic hydrolysates that were obtained through a two-step treatment at optimized conditions were fermented using Pichia stipitis for ethanol production, without any further detoxification. The maximum ethanol production was 4.84 g/L, corresponding to a theoretical ethanol yield of 82.52%, which is comparable to those of intentionally made hydrolyzates as controls.