Maize Silage as a Feedstock for Cellulosic Ethanol Production: Impact of Brown Midrib Lignin Variants On Bioprocessing Performance.

Effective storage of cellulosic feedstocks that preserves quality is critical for supplying biorefineries for the production of biofuels.  Ensiling is a well developed technology for preserving herbaceous feedstocks for animal feed.  We present the effect of brown midrib lignin mutations on rates and yields of cellulosic ethanol production from maize silage and dry stover.  Both stover and silage from commercial sources were pretreated using liquid hot water (160-180°C) and assessed by enzymatic hydrolysis and fermentation using the glucose/xylose fermenting Purdue recombinant S. cerevisiae 424A (LNH-ST).  At 20% solids concentration (200 g/L), silage achieved higher yields of fermentable sugars than stover.  Lignin altered bmr stover and silage achieved higher yields of sugars than the non-bmr stover or silage pretreated under the same conditions.  At the optimal pretreatment conditions, bmr silage achieved 62% of theoretical yield of glucose within 24 hours of enzymatic hydrolysis (15 FPU cellulase per gram glucan) compared to 50% yield from non-bmr silage.  Sugars from both silage varieties fermented to ethanol at high yields using the Purdue recombinant yeast strain, indicating bmr silage may be an ideal feedstock for cellulosic ethanol production.