Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

The recalcitrance of lignocellulosic materials to biochemical conversion is a major hurdle for cost-effective production of cellulosic sugars that can be processed into fuels and valuable chemicals. In this study, Alamo switchgrass (Panicum virgatum L.) was genetically transformed to suppress the expression of 4-coumarate-CoA ligase (4CL). The transgenic plants were determined to have lignin content reductions of up to 5.8%. The ratios of acid soluble lignin (ASL) to acid insoluble lignin (AIL) in transgenic plants were 21.4-64.3% higher than those of conventional biomass. Both conventional and transgenic plants were pretreated with alkalis at mild temperatures: lime at 50C and the combination of lime and NaOH at 21C, followed by enzymatic hydrolysis with commercial cellulases and xylanases. At the recommended conditions (0.1 g/g raw biomass and 12 h) for lime pretreatment at 50C, the glucan and xylan conversions of transgenic switchgrass were 12% and 10%, respectively, higher than those of conventional plant. These increases were reduced to 7% and 8% for glucan and xylan conversions, respectively, when the best conditions (0.025 g lime/g raw biomass, 0.1 g NaOH/g raw biomass, and 6 h) for combined alkali pretreatment at 21C were employed. The results show that down-regulation of 4CL gene promoted enzymatic hydrolysis of plant cell walls following mild alkaline pretreatments.