title: Catalyst transport in corn stover internodes: elucidating transport mechanisms using Direct Blue-I.
abstract: The transport of catalysts (chemicals and enzymes) within plant biomass is believed to be a major bottleneck during thermochemical pretreatment and enzymatic conversion of lignocellulose. Subjecting biomass to size reduction and mechanical homogenization can reduce catalyst transport limitations; however, such processing adds complexity and cost to the overall process. Using high-resolution light microscopy, we have monitored the transport of an aqueous solution of Direct Blue-I (DB-I) dye through intact corn internodes under a variety of impregnation conditions. DB-I is a hydrophilic anionic dye with affinity for cellulose. This model system has enabled us to visualize likely barriers and mechanisms of catalyst transport in corn stems. Microscopic images were compared with calculated degrees of saturation (i.e., volume fraction of internode void space occupied by dye solution) to correlate impregnation strategies with dye distribution and transport mechanisms. Results show the waxy rind exterior and air trapped within individual cells to be the major barriers to dye transport, whereas the vascular bundles, apoplastic continuum (i.e., the intercellular void space at cell junctions), and fissures formed during the drying process provided the most utilized pathways for transport. Although representing only 20-30% of the internode volume, complete saturation of the apoplast and vascular bundles by fluid allowed dye contact with a majority of the cells in the internode interior.
authors.affiliation: National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401, USA. Sridhar_viamajala@nrel.gov
authors.forename: Sridhar
authors.initials: S
authors.lastname: Viamajala
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Selig
authors.forename: Todd B
authors.initials: TB
authors.lastname: Vinzant
authors.forename: Melvin P
authors.initials: MP
authors.lastname: Tucker
authors.forename: Michael E
authors.initials: ME
authors.lastname: Himmel
authors.forename: James D
authors.initials: JD
authors.lastname: McMillan
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Decker
mesh_terms: D001391:Azo Compounds; D001693:Biological Transport, Active / Q000502:physiology; D002384:Catalysis; D002463:Cell Membrane Permeability / Q000502:physiology*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000737:chemistry* / Q000378:metabolism; D035261:Plant Components, Aerial / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D011312:Pressure; D013696:Temperature; D014343:Trypan Blue; D003313:Zea mays / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*
chemical_list: D001391:Azo Compounds; D017077:Culture Media, Conditioned; C009000:pontamine sky blue; D014343:Trypan Blue