Development of a Highly Efficient Pretreatment Sequence for the Enzymatic Saccharification of Loblolly Pine Wood

The efficient pretreatment of lignocellulosic materials for bioenergy production is a critical step upon which efficient saccharification is highly dependent, particularly in softwoods due to both their high lignin content and condensed lignin structures. In the present study, preliminary pretreatment steps (e.g., Wiley milling, acetone extraction, autohydrolysis, and disc refining) and economical subsequent/core-pretreatment steps (e.g., reagents immersion, hydrothermolysis, dilute acid hydrolysis, and ionic liquids treatment) were systematically investigated to identify which combinations led to effective enzymatic saccharification of loblolly pine wood, the dominant softwood resource in the US. The results demonstrated that 85% phosphoric acid based immersions were highly efficient for both cellulose crystallinity degradation and enzymatic hydrolysis, and thus can be included as core pretreatment steps. The highest glucan recovery yield obtained was 93.0% after enzymatic hydrolysis when a pretreatment sequence consisting of autohydrolysis, disc refining, acetone drying, and 85% phosphoric acid immersion (50 °C, 1 h) was employed.