Fiber modifications by organosolv catalyzed with H2SO4 improves the SSF of Pinus radiata

• Bioethanol from P. radiata is a promising alternative for fuel in Chile.
• Organosolv catalyzed by an appropriate concentration of H2SO4 promotes structural and morphological changes in P. radiata, such as the formation of lignin droplets.
• The formation of lignin droplets increases the digestibility of the pretreated material to achieve a high conversion of cellulose to glucose.
• The proper dosage of last-generation enzyme Cellic Ctec®3 to achieve high cellulose to glucose conversion is 0044 g of enzyme per g of dry pretreated material.
• High ethanol concentrations and yields in dry wood basis were obtained through SSF and fed-batch SSF using the thermotolerant strain of Saccharomyces cereviseae IR2-9a at high substrate loadings.
• With the feb-batch SSF strategy the viscosity of the formulations are kept low, and good mass transfer is maintained throughout the experiments.
• From the results obtained by SSF, either in batch or fed-batch mode, it follows that high concentrations of ethanol are achieved thanks to the good enzymatic accessibility and digestibility of the pretreated material obtained.
• Using the fed-batch SSF strategy increases the volumetric productivity (QP) of the reactions.
• Cellulase Cellic Ctec®3 enzyme complex maintains a suitable catalytic activity at 40 °C and is not affected by high concentrations of ethanol.
• The highest ethanol concentration obtained was 85.01 g/L. This final concentration inhibits the fermentation by thermotolerant S. cerevisiae IR2-9a.

Pinus radiata is an appropriate feedstock for the production of second-generation bioethanol through a biochemical platform due to its high content of fermentable sugars. However, because of this tree’s recalcitrance, a suitable pretreatment is necessary. In this paper, the effect of the concentration of H2SO4 as a catalyst for the organosolv pretreatment for this raw material was studied. It was determined that a concentration of 1.1% of H2SO4 promotes structural and morphological changes, such as the formation of lignin droplets, which increase the digestibility of the pretreated material to achieve an efficient conversion of cellulose to glucose of 94% using the proper dosage of a last-generation cellulase complex. Because of the good digestibility of the pretreated material obtained, it was possible to obtain high concentrations of ethanol, reaching 85.01 g/L after 72 h of reaction, working with fed-batch simultaneous saccharification and fermentation at 40 °C at high substrate loadings using the thermotolerant strain of Saccharomyces cerevisiae IR2-9a. The importance of obtaining high concentrations of ethanol is that if the concentrations are above 4%, the cost of the distillation process is decreased.