Bioorganosolv pretreatments of P. radiata by a brown rot fungus (Gloephyllum trabeum) and ethanolysis

Pinus radiata wood chips were pretreated with the brown rot fungus Gloephyllum trabeum for 3 weeks followed by an organosolv delignification with ethanol:water mixture at pH 2. The organosolv process was assessed using biotreated material that showed a high viscosity loss and a mass loss ranging from 6% to 8%. The experiment was designed to optimize the organosolv conditions, ethanol:water ratio and H factor (factor that combines temperature and time in one variable) to obtain the highest ethanol yield by simultaneous enzymatic saccharification and fermentation (SSF) for 96 h at 10% consistency. The optimized conditions for organosolv process for biotreated material were: ethanol:water mixture (60/40, v/v) and 1156 H factor (185 °C, 18 min); the optimized conditions for the control (chips without biotreatment) were: ethanol:water mixture (60/40, v/v) and 6000 H factor (200 °C, 32 min). The experimental ethanol yields obtained at these conditions were 63.8% and 64.3% (wood basis) for biotreated material and control, respectively. The maximum amount of ethanol that could be produced from P. radiata is 252 g ethanol/kg wood, assuming total glucose conversion into ethanol. The results indicate that the obtained ethanol was 161 g ethanol/kg wood from both materials. The biotreatment of the wood before the organosolv process improved solvent accessibility. To obtain the same ethanol yield, lower process severity was required in the biotreated samples in comparison with the control.