Monday, April 30, 2007
5B-25

Differentiation in activity of fractions of stay green corn stover for hot water pretreatment and cellulase saccharification

Meijuan Zeng1, Joan Goetz2, Richard Hendrickson1, Chia-Ping Huang3, Debra Sherman3, Nathan S. Mosier4, and Michael R. Ladisch5. (1) LORRE, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 57866, (2) LORRE/CSR, Purdue University, West Lafayette, IN 57866, (3) Life Science Microscopy Facility, Purdue University, West Lafayette, IN 47907, (4) LORRE/Ag. and Bio. Engineering, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907, (5) Lorre/abe, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 57866

Corn stover is a heterogeneous substrate consisting of different fractions including leaves, stalk fiber and stalk pith.  Tissue types and proportions in these fractions are not uniform which result in different cell structures, average cell wall thickness and lignin distribution.  These factors may have different impacts on enzyme digestion, since the lignin barrier (content/distribution) and cell wall thickness are believed to be substrate related factors that influence the effectiveness of enzymatic hydrolysis of cellulose in lignocellulosic feedstocks.  The hypothesis being tested in this research addresses potential differences of intrinsic reactivity of different parts of stay green corn stover (leaves, stalk fiber and stalk pith).  Carbohydrate analysis shows that pith is more readily hydrolyzed than leaves and fiber at cellulase level equivalent to 5 FPU Spezyme CP / g glucan.  Hot water pretreatment at 190°C for 15 min removes 40% to 50% hemicellulose in these fractions, respectively, although structural changes in the cell wall are not evident when the residual material is imaged by scanning electron microscopy.  Enzyme hydrolysis of pretreated and washed fractions of leaves and pith exhibit much higher glucose conversion than the fractions that has not been pretreated.  Pretreated fiber (from the rind) is still resistant to hydrolysis and shows 2/3 lower glucose formation than pretreated leaf or pith at low enzyme loadings equivalent to about 5 FPU Spezyme CP/g glucan.

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