Publications by Colleges and Departments (MSU - Bozeman)
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Item Effect of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin Properties and Suitability as a Phenol Replacement in Phenol-Formaldehyde Wood Adhesives(American Chemical Society, 2022-12) Saulnier, Brian K.; Siahkamari, Mohsen; Singh, Sandip K.; Nejad, Mojgan; Hodge, David B.Corn stover was subjected to dilute sulfuric acid pretreatment to assess the impact of pretreatment conditions on lignin extractability, properties, and utility as a phenol replacement in wood phenol-formaldehyde (PF) adhesives. It was identified that both formic acid and NaOH could extract and recover 60–70% of the lignin remaining after pretreatment and enzymatic hydrolysis under the mildest pretreatment conditions while simultaneously achieving reasonable enzymatic hydrolysis yields (>60%). The availability of reaction sites for the incorporation of lignins into the PF polymer matrix (i.e., unsubstituted phenolic hydroxyl groups) was shown to be strongly impacted by the pretreatment time and the recovery. Finally, a lignin-based wood adhesive was formulated by replacing 100% of the phenol with formic-acid-extracted lignin, which exhibited a dry shear strength exceeding a conventional PF adhesive. These findings suggest that both pretreatment and lignin extraction conditions can be tailored to yield lignins with properties targeted for this co-product application.Item Particle classification by image analysis improves understanding of corn stover degradation mechanisms during deconstruction(Elsevier BV, 2023-03) Cousins, Dylan S.; Pedersen, Kristian P.; Otto, William G.; Rony, Asif Hasan; Lacey, Jeffrey A.; Aston, John E.; Hodge, David B.iomass feedstock heterogeneity is a principal roadblock to implementation of the biorefinery concept. Even within an identical cultivar of corn stover, different bales contain not only varying abundance moisture, ash, glucan, and other chemical compounds, but also varying abundance of tissue anatomies (e.g., leaf, husk, cob, or stalk). These different anatomical components not only differ in their response to pretreatment and enzymatic hydrolysis to glucose, but also vary in their mechanical and conveyance properties. Although this heterogeneous nature of corn stover feedstock has been identified as a challenge, a fundamental knowledge gap of how these tissues behave during biorefining processing remains. In this work, we demonstrate the use of a commercial fiber image analyzer typically used for wood fiber characterization to monitor the particle size and shapes of non-woody feedstock during milling, pretreatment, and hydrolysis. Additionally, we present novel use of Gaussian process classification to distinguish bundle, parenchyma, and fiber particles to an accuracy of 96.4%. Quantitative probability distribution plots for characteristics such as length and roundness allow elucidation of particle morphology as pretreatment and enzymatic hydrolysis progress. In both stalk pith and stalk rind, particles peel into individual cells whose walls are subsequently fragmented during enzymatic hydrolysis.Item Lignin properties and cell wall response to deconstruction by alkaline pretreatment and enzymatic hydrolysis in brown midrib sorghums(Elsevier BV, 2022-04) Singh, Sandip K.; Saulnier, Brian K.; Hodge, David B.Lignin has an adverse impact on the deconstruction of plant cell wall biopolymers in biorefining processes and its reduction and/or alteration during biosynthesis is one target for decreasing plant cell wall recalcitrance. In this work, the impact of two brown midrib mutations (bmr6 and bmr12) in two sorghum background lines (the commercial hybrid Atlas and near-isogenic BTx623) on lignin properties and the plants’ response to cell wall deconstruction to monomeric sugars via alkaline pretreatment and enzymatic hydrolysis is investigated with the goal of assessing how differences in lignin content and properties impact the plant’s response to pretreatment. We identify that both bmr sorghum lines show significantly lower abundance of water-extractable sugars (glucose, sucrose, and fructose) and alkali-saponifiable p-coumarate. Furthermore, both these properties exhibited identical trends across both background lines. Next, both untreated and mild alkali-pretreated bmr sorghums were shown to exhibit higher glucose hydrolysis yields following enzymatic hydrolysis than the control lines. Following pretreatment, the Atlas bmr sorghums exhibited more lignin solubilization and the solubilized lignin was of lower molar mass than the background control line suggesting that differences in the lignin response to pretreatment resulted these differences. Finally, significant differences were observed in the lignin content, lignin monomer distribution, and inter-unit linkages in the Atlas bmr line relative to the control line with key differences including lower syringyl monomer content in both bmr lines, higher relative abundance of β-O-4 linkages in the bmr6 line, and the presence of 5-hydroxy guaiacyl monomers and benzodioxane (α-O-5/β-O-4) linkages in the bmr12 line.Item Near-Infrared Spectroscopy can Predict Anatomical Abundance in Corn Stover(Frontiers Media SA, 2022-02) Cousins, Dylan S.; Otto, William G.; Rony, Asif Hasan; Pedersen, Kristian P.; Aston, John E.; Hodge, David B.Feedstock heterogeneity is a key challenge impacting the deconstruction and conversion of herbaceous lignocellulosic biomass to biobased fuels, chemicals, and materials. Upstream processing to homogenize biomass feedstock streams into their anatomical components via air classification allows for a more tailored approach to subsequent mechanical and chemical processing. Here, we show that differing corn stover anatomical tissues respond differently to pretreatment and enzymatic hydrolysis and therefore, a one-size-fits-all approach to chemical processing biomass is inappropriate. To inform on-line downstream processing, a robust and high-throughput analytical technique is needed to quantitatively characterize the separated biomass. Predictive correlation of near-infrared spectra to biomass chemical composition is such a technique. Here, we demonstrate the capability of models developed using an “off-the-shelf,” industrially relevant spectrometer with limited spectral range to make strong predictions of both cell wall chemical composition and the relative abundance of anatomical components of the corn stover, the latter for the first time ever. Gaussian process regression (GPR) yields stronger correlations (average R2v = 88% for chemical composition and 95% for anatomical relative abundance) than the more commonly used partial least squares (PLS) regression (average R2v = 84% for chemical composition and 92% for anatomical relative abundance). In nearly all cases, both GPR and PLS outperform models generated using neural networks. These results highlight the potential for coupling NIRS with predictive models based on GPR due to the potential to yield more robust correlations.Item Effect of catalyst and reaction conditions on aromatic monomer yields, product distribution, and sugar yields during lignin hydrogenolysis of silver birch wood(2020-11) Phongpreecha, Thanaphong; Christy, Kendall F.; Singh, Sandip K.; Hao, Pengchao; Hodge, David B.The impact of catalyst choice and reaction conditions during catalytic hydrogenolysis of silver birch biomass are assessed for their effect on aromatic monomer yields and selectivities, lignin removal, and sugar yields from enzymatic hydrolysis. At a reaction temperature of 220 °C with no supplemental H2, it was demonstrated that both Co/C and Ni/C exhibited aromatic monomer yields of >50%, which were close to the theoretical maximum expected for the lignin based on total β-O-4 content and exhibited high selectivities for 4-propylguaiacol and 4-propylsyringol. Pd/C exhibited a significantly different set of products, and using a model lignin dimer, showed a product profile that shifted upon inclusion of supplemental H2, suggesting that the generation of surface hydrogen is critical for this catalyst system. Lignin removal during hydrogenolysis could be correlated to glucose yields and inclusion of lignin depolymerizing catalysts significantly improves lignin removal and subsequent enzymatic hydrolysis yields.Item Impact of dilute acid pretreatment conditions on p-coumarate removal in diverse maize lines(2020-10) Saulnier, Brian K.; Phongpreecha, Thanaphong; Singh, Sandip K.; Hodge, David B.Prior work has identified that lignins recovered from dilute acid-pretreated corn stover exhibit superior performance in phenol–formaldehyde resins used in wood adhesive applications when compared to diverse process-modified lignins derived from other sources. This improved performance is hypothesized to be due to the higher content of unsubstituted phenolic groups specifically p-coumarate lignin esters. In this work, a diverse set of corn stover samples are employed that exhibit diversity in p-coumarate content and total lignin content to explore the relationship between dilute acid pretreatment conditions, p-coumarate ester hydrolysis, xylan solubilization, and the resulting glucose enzymatic hydrolysis yields. The goal of this study is to identify pretreatment conditions that preserve a significant fraction of the p-coumarate esters while simultaneously achieving high enzymatic hydrolysis yields. Kinetic parameters for p-coumarate ester hydrolysis were quantified and pretreatment-biomass combinations were identified that result in glucose hydrolysis yields of more than 90% while retaining nearly 50 mg p-coumarate/g lignin.Item Xylan Is Critical for Proper Bundling and Alignment of Cellulose Microfibrils in Plant Secondary Cell Walls(2021-09) Crowe, Jacob D.; Hao, Pengchao; Pattathil, Sivakumar; Pan, Henry; Ding, Shi-You; Hodge, David B.; Krüger Jensen, JacobPlant biomass represents an abundant and increasingly important natural resource and it mainly consists of a number of cell types that have undergone extensive secondary cell wall (SCW) formation. These cell types are abundant in the stems of Arabidopsis, a well-studied model system for hardwood, the wood of eudicot plants. The main constituents of hardwood include cellulose, lignin, and xylan, the latter in the form of glucuronoxylan (GX). The binding of GX to cellulose in the eudicot SCW represents one of the best-understood molecular interactions within plant cell walls. The evenly spaced acetylation and 4-O-methyl glucuronic acid (MeGlcA) substitutions of the xylan polymer backbone facilitates binding in a linear two-fold screw conformation to the hydrophilic side of cellulose and signifies a high level of molecular specificity. However, the wider implications of GX–cellulose interactions for cellulose network formation and SCW architecture have remained less explored. In this study, we seek to expand our knowledge on this by characterizing the cellulose microfibril organization in three well-characterized GX mutants. The selected mutants display a range of GX deficiency from mild to severe, with findings indicating even the weakest mutant having significant perturbations of the cellulose network, as visualized by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). We show by image analysis that microfibril width is increased by as much as three times in the severe mutants compared to the wild type and that the degree of directional dispersion of the fibrils is approximately doubled in all the three mutants. Further, we find that these changes correlate with both altered nanomechanical properties of the SCW, as observed by AFM, and with increases in enzymatic hydrolysis. Results from this study indicate the critical role that normal GX composition has on cellulose bundle formation and cellulose organization as a whole within the SCWs.Item Lignin-Based Polyurethanes: Opportunities for Bio-Based Foams, Elastomers, Coatings and Adhesives(2019-07-19) Alinejad, Mona; Henry, Christian; Nikafshar, Saeid; Gondaliya, Akasha; Bagheri, Sajad; Chen, Nusheng; Singh, Sandip K.; Hodge, David B.; Nejad, MojganPolyurethane chemistry can yield diverse sets of polymeric materials exhibiting a wide range of properties for various applications and market segments. Utilizing lignin as a polyol presents an opportunity to incorporate a currently underutilized renewable aromatic polymer into these products. In this work, we will review the current state of technology for utilizing lignin as a polyol replacement in different polyurethane products. This will include a discussion of lignin structure, diversity, and modification during chemical pulping and cellulosic biofuels processes, approaches for lignin extraction, recovery, fractionation, and modification/functionalization. We will discuss the potential of incorporation of lignins into polyurethane products that include rigid and flexible foams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating lignin in polyurethane formulations, potential solutions and approaches that have been taken to resolve those issues.