Ultrastructure and Enzymatic Hydrolysis of Deuterated Switchgrass

Abstract

Neutron scattering of deuterated plants can provide fundamental insight into the structure of lignocellulosics in plant cell walls and its deconstruction by pretreatment and enzymes. Such plants need to be characterized for any alterations to lignocellulosic structure caused by growth in deuterated media. Here we show that glucose yields from enzymatic hydrolysis at lower enzyme loading were 35% and 30% for untreated deuterated and protiated switchgrass, respectively. Lignin content was 4% higher in deuterated switchgrass but there were no significant lignin structural differences. Transmission electron microscopy showed differences in lignin distribution and packing of fibers in the cell walls that apparently increased surface area of cellulose in deuterated switchgrass, increasing cellulose accessibility and lowering its recalcitrance. These differences in lignification were likely caused by abiotic stress due to growth in deuterated media.

Nanoscale FTIR and Mechanical Mapping of Plant Cell Walls for Understanding Biomass Deconstruction

“…Therefore, these regions appear darker with toluidine blue staining, had higher fluorescence because of autofluorescence of lignin and higher contrast in TEM as lignin has higher affinity toward permanganate oxidation than polysaccharides. 2 For all three trees, there are regions of thick cell corners extending into middle lamellae that are rich in lignin deposits. The dimensions of plant cells that were not adjacent to rays ranged in 15−25 μm (major axis) and 12−20 μm (minor axis).…”

“…The middle lamellae and cell corners contain higher concentration of lignin than secondary cell walls. Therefore, these regions appear darker with toluidine blue staining, had higher fluorescence because of autofluorescence of lignin and higher contrast in TEM as lignin has higher affinity toward permanganate oxidation than polysaccharides . For all three trees, there are regions of thick cell corners extending into middle lamellae that are rich in lignin deposits.…”

“…TEM imaging of stained/immunolabeled plant tissues can provide nanometer scale resolution of lignin distribution. 2 However, it is difficult to distinguish spatial variations in chemical structure and related properties among the cell wall polymers at the nanoscale (∼20 nm). New atomic force microscopy (AFM)based techniques like nano-FTIR and quantitative nanomechanical property mapping through PeakForce Tapping mode (PF QNM) 3 introduce avenues to study the spatial distribution of chemical structure and mechanical properties at high resolution and without any modification to the native chemical structure.…”

“…Ultraviolet, infrared, Raman, optical and fluorescence microscopy can distinguish spatial differences in cell wall polymers like cellulose, hemicelluloses, and lignin at the micrometer scale. TEM imaging of stained/immunolabeled plant tissues can provide nanometer scale resolution of lignin distribution . However, it is difficult to distinguish spatial variations in chemical structure and related properties among the cell wall polymers at the nanoscale (∼20 nm).…”

Production of Sugar Feedstocks for Fermentation Processes from Selected Fast Growing Grasses

“…Perennial grasses have been increasingly used as energy crops (mainly as solid biofuels and for biogas production) [8,9], because of the higher cellulose and lignin contents, as compared to the biomass of annual crops, that results in a higher heating value [10]. Fast growing grasses, such as switchgrass (Panicum virgatum L.) [11][12][13], Miscanthus giganetus JM Greef and Deuter ex Hodk. and Renvoize [14,15], and sweet sorghum (Sorghum bicolor L.) [16][17][18], have been most studied.…”