Improved sugar yield upon steam explosion and enzymatic saccharification of field-grown poplar downregulated for cinnamyl alcohol dehydrogenase 1

Genetic modification of lignocellulosic biomass can enhance its processability by reducing its recalcitrance to pretreatment and enzymatic conversion to chemicals such as biofuels. Downregulation of cinnamyl alcohol dehydrogenase 1 (CAD1) in poplar results in the increased incorporation of sinapaldehyde in the lignin polymer. Here, we investigated steam explosion as a pretreatment strategy for the enzymatic hydrolysis of field-grown CAD1-downregulated and wild-type (WT) poplar. Steam explosion at 210°C for 90 s resulted in a significantly higher lignin reduction of 25% for CAD wood, compared to 15% for WT wood. Under limited conditions at 8.4% solid loading and 8 filter paper units of Cellic Ctec3 HS per gram dry weight, enzymatic hydrolysis resulted in a significantly higher average glucose yield of 76% for CAD wood compared to 60% for WT wood. Our data show that steam explosion pretreatment of CAD1-modified poplar is a promising strategy to improve enzymatic hydrolysis without the need for additional chemicals.