11-20: Tissue-specific biomass recalcitrance in corn stover pretreated with liquid hot-water: enzymatic hydrolysis and SEM imaging

Lignin content, composition, distribution as well as cell wall thickness, structures, and type of tissue all have measurable effects on enzymatic hydrolysis of cellulose in lignocellulosic feedstocks.  Our work combined compositional analysis, pretreatment, enzyme hydrolysis and SEM imaging for fractionated pith, rind, and leaf tissues from a hybrid stay-green corn, in order to identify the role of structural characteristics on enzyme hydrolysis of cell walls.  Hydrolysis followed the sequence rind < leaves < pith,  with 75% conversion to glucose achieved with 9 mg enzyme protein/ g glucan or 3.6 mg protein/ total solids and  90% with 108 mg protein/ g glucan or 43.2 mg protein/ total solids in 24 hours.  Physical fractionation of corn stalks or other C₄ grasses into soft and hard tissue types could reduce cost of cellulose conversion by enabling reduced enzyme loadings to hydrolyze soft tissue, and directing the hard tissue to other uses.  The amount of lignin alone remaining after pretreatment of the different fractions is about the same, so differences in lignin content do not explain the differences in enzymatic hydrolysis. SEM images show sugar yields correlate with changes in plant cell wall structure both before and after liquid hot water pretreatment.

Note:  Work in press (Feb. 2012): “Enzyme Hydrolysis and Imaging of Fractionated Corn Stalk Tissues Pretreated with Liquid Hot Water Part I”, Biotechnol. Bioeng.; and 2. “Enzyme Hydrolysis and Imaging of Fractionated Corn Stalk Tissues Pretreated with Liquid Hot Water Part II”, Biotechnol. Bioeng.