Investigating Lignin Key Features in Maize Lignocelluloses Using Infrared Spectroscopy

Lignins and their cross-linking to hemicelluloses detrimentally affect the cellulose-to-ethanol conversion of grass lignocelluloses. Screening appropriate grass cell walls and their compositional changes during the various steps of the process calls for a high-throughput analytical technique. Such a performance can be fulfilled by Fourier transform mid-infrared (FT-MIR) spectroscopy. In the present paper, a set of maize cell walls from mature stems were selected, including brown midrib samples. Lignin fractions were isolated by mild acidolysis to obtain a set of purified maize lignin standards. The lignin content and the percentage of lignin-derived p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) thioacidolysis monomers were determined. In addition, the composition of cell wall polysaccharides, as well as the amount of ester-linked p-coumaric (CA) and ferulic (FA) acids, was measured by wet chemistry. Partial least square (PLS) analyses were applied to infrared and chemical data of cell walls. The resulting models showed a good predictive ability with regard to the lignin content, to the frequency of S (or G) thioacidolysis monomers, and to the level of ester-linked CA of maize cell walls. The loading plots and regression coefficients revealed relevant infrared absorption bands

Cord blood volume reduction using an automated system (Sepax) vs. a semi-automated system (Optipress II) and a manual method (hydroxyethyl starch sedimentation) for routine cord blood banking: a comparative study.

International audienceBackground With the development of cord blood banking, solutions have to be found to solve the storage space problem, by reducing the volume of cord blood units (CBU). Methods We compared total nucleated cell (TNC) and CD34(+) cell counts before and after processing with three different CBU volume reduction methods used consecutively in our bank: a manual method based on hydroxyethyl starch sedimentation (HES) (n=447), a top-and-bottom (TB) semi-automated method (n=181) using Optipress II, and the Sepax automated method (n=213). Statistical analysis was done using t-tests, linear regression and Spearman correlation coefficients. Adjusted variables included TNC, CD34(+) cell counts, CD34(+) cell percentage and CB volume before processing. Results TNC recovery was higher with Sepax (80.3+/-7.7%) than with HES (76.8+/-9.1%) and TB (60.7+/-13.5%) (P<0.0001, both). It was higher with HES than with TB (P<0.0001). CD34(+) cell recovery was higher with Sepax (86+/-11.6%) than with HES (81.5+/-12.5%) and TB (82.0+/-17.7%) (P<0.008 and <0.0001, respectively) and results with HES and TB were not significantly different (P=0.7). Interestingly, with Sepax, TNC and CD34(+) cell recoveries were not correlated with pre-processing values (P=0.8 and 0.4, respectively). Discussion In conclusion, the Sepax volume reduction method allows higher TNC and CD34(+) cell recoveries

Dry separation of ground maize stems provides fractions with distinct enzymatic degradation patterns

Dry separation of ground maize stems provides fractions with distinct enzymatic degradation patterns. 3. International Symposium on Green Chemistry (ISGC 2015

Dry separation of ground maize stems provides fractions with distinct enzymatic degradation patterns

The enzymatic saccharification of lignocelluloses depends on their physical state and chemical composition, which is related to tissue properties. The objective of the present work was to study the enzymatic degradation pattern of particles isolated through a dry separation process from maize plant. Whole plants without ears were ground and fractionated by turbo-separation. The fine- and medium-size particles were submitted to electrostatic sorting. The IMATORE reactor [1] allowed us to monitor the compositional changes and size evolution of the particles during saccharification. In all fractions, glucose and xylose were the major sugars. However, minor sugars displayed distinct distributions, fine particles being richer in arabinose and uronic acids. While the large particles were found to be lignin-richer, the fine ones exhibited the lowest lignin amount and a higher ratio of syringyl over guaiacyl units. The enzymatic degradation patterns differed between fractions. Not unexpectedly, large and fine particles were respectively the less and the more degraded, as revealed by their compositional and size changes. Interestingly, positive-deviated medium size particles had a particular behaviour with most of the sugar released during the first 30 min without any noticeable change in particle size. The negative-deviated medium size particles behaved like the large ones. The present work confirms that plant heterogeneity should be considered in the biorefinery chain. Next steps will be (i) to find the relationships of particles degradation pattern to stem histology and (ii) to improve the dry separation process in order to increase the saccharification yield

Ferulate and lignin cross-links increase in cell walls of wheat grain outer layers during late development

International audienceImportant biological, nutritional and technological roles are attributed to cell wall polymers from cereal grains. The composition of cell walls in dry wheat grain has been well studied, however less is known about cell wall deposition and modification in the grain outer layers during grain development. In this study, the composition of cell walls in the outer layers of the wheat grain (Triticum aestivum Recital cultivar) was investigated during grain development, with a focus on cell wall phenolics. We discovered that lignification of outer layers begins earlier than previously reported and long before the grain reaches its final size. Cell wall feruloylation increased in development. However, in the late stages, the amount of ferulate releasable by mild alkaline hydrolysis was reduced as well as the yield of lignin-derived thioacidolysis monomers. These reductions indicate that new ferulate-mediated cross-linkages of cell wall polymers appeared as well as new resistant interunit bonds in lignins. The formation of these additional linkages more specifically occurred in the outer pericarp

Enzymatic degradation of maize shoots: monitoring of chemical and physical changes reveals different saccharification behaviors

International audienceBackground : The recalcitrance of lignocellulosics to enzymatic saccharification has been related to many factors, including the tissue and molecular heterogeneity of the plant particles. The role of tissue heterogeneity generally assessed from plant sections is not easy to study on a large scale. In the present work, dry fractionation of ground maize shoot was performed to obtain particle fractions enriched in a specific tissue. The degradation profiles of the fractions were compared considering physical changes in addition to chemical conversion.Results : Coarse, medium and fine fractions were produced using a dry process followed by an electrostatic separation. The physical and chemical characteristics of the fractions varied, suggesting enrichment in tissue from leaves, pith or rind. The fractions were subjected to enzymatic hydrolysis in a torus reactor designed for real-time monitoring of the number and size of the particles. Saccharification efficiency was monitored by analyzing the sugar release at different times. The lowest and highest saccharification yields were measured in the coarse and fine fractions, respectively, and these yields paralleled the reduction in the size and number of particles. The behavior of the positively- and negatively-charged particles of medium-size fractions was contrasted. Although the amount of sugar release was similar, the changes in particle size and number differed during enzymatic degradation. The reduction in the number of particles proceeded faster than that of particle size, suggesting that degradable particles were degraded to the point of disappearance with no significant erosion or fragmentation. Considering all fractions, the saccharification yield was positively correlated with the amount of water associated with [5–15 nm] pore size range at 67% moisture content while the reduction in the number of particles was inversely correlated with the amount of lignin.Conclusion : Real-time monitoring of sugar release and changes in the number and size of the particles clearly evidenced different degradation patterns for fractions of maize shoot that could be related to tissue heterogeneity in the plant. The biorefinery process could benefit from the addition of a sorting stage to optimise the flow of biomass materials and take better advantage of the heterogeneity of the biomass

Rôles de la lignification du grain de céréales

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Brachypodium cell wall mutant with enhanced saccharification potential despite increased lignin content

Plant lignocellulosic biomass, mostly composed of cell walls, is one of the largest, mostly untapped, reserves of renewable carbon feedstock on the planet. Energy-rich polysaccharide polymers of plant cell walls can be broken down to produce fermentable sugars used to produce bioethanol. However, the complex structure of plant cell walls, and in particular, the presence of lignin, makes them recalcitrant to enzymatic degradation. Reducing this recalcitrance represents a major technological challenge. Brachypodium distachyon is an excellent model to identify parameters underlying biomass quality of energy grasses. In this work, we identified a mutant line spa1 with a so far undescribed phenotype combining brittleness with increased elasticity of the internodes. Mutant cell walls contain less crystalline cellulose and changes in hemicellulose and lignin quality and quantity. Using a dedicated reactor to follow in real-time, the evolution of straw particle size and sugar release during enzymatic digestion, we show that, despite the increased lignin content, the spa1 mutant has a dramatic reduced recalcitrance to saccharification compared to the WT. These observations demonstrate that other parameters besides lignin content are relevant for the improvement of biomass recalcitrance in energy grasses