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GLBRC's Publications

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Publications

When it comes to interdisciplinary collaboration, the titles of GLBRC publications speak for themselves. Each new year of operation has seen more publications from multiple labs that span the four Research Areas, accelerating the Center's production of the basic research that generates technology to convert cellulosic biomass to advanced biofuels.

Publications

A co-solvent hydrolysis strategy for the production of biofuels: process synthesis and technoeconomic analysis

Wangyun Won; Ali H. Motagamwala; James A. Dumesic; Christos T. Maravelias

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2017

We develop an integrated strategy for the production of ethanol from lignocellulosic biomass. Cellulose and hemicellulose fractions are first hydrolyzed into sugars using a mixture of γ-valerolactone (GVL), water, and toluene as a solvent containing dilute sulfuric acid as a catalyst, and the sugars are then co-fermented into ethanol over engineered yeast strains. Separation subsystems are designed to effectively recover GVL and toluene for reuse in biomass hydrolysis, and to recover lignin and humins for heat and power generation. We also develop an alternative process, in which we recover sugars and GVL from the residual biomass. To minimize utility requirements, we conduct heat integration, which allows us to meet all heating requirement using biomass residues. Finally, we perform a range of system-level analyses to identify the major cost and technological drivers. The proposed strategy is shown to be cost-competitive with other strategies.

A superstructure-based framework for bio-separation network synthesis

WenZhao Wu; Kirti Yenkie; Christos T. Maravelias

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2017

Modern biotechnologies enable the production of chemicals using engineered microorganisms. However, the cost of downstream recovery and purification steps is high, which means that the feasibility of bio-based chemicals production depends heavily on the synthesis of cost-effective separation networks. To this end, we develop a superstructure-based framework for bio-separation network synthesis. Based on general separation principles and insights obtained from industrial processes for specific products, we first identify four separation stages: cell treatment, product phase isolation, concentration and purification, and refinement. For each stage, we systematically implement a set of connectivity rules to develop stage-superstructures, all of which are then integrated to generate a general superstructure that accounts for all types of chemicals that can be produced using microorganisms. We further develop a superstructure reduction method to solve specific instances, based on product attributes, technology availability, case-specific considerations, and final product stream specifications. A general optimization model, including short-cut models for all technologies, is formulated. The proposed framework enables preliminary synthesis and analysis of bio-separation networks, and thus estimation of separation costs.

Biochemical transformation of lignin for deriving valued commodities from lignocellulose

Daniel L. Gall; J. Ralph; Timothy J. Donohue; Daniel R. Noguera

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2017

The biochemical properties of lignin present major obstacles to deriving societally beneficial entities from lignocellulosic biomass, an abundant and renewable feedstock. Similar to other biopolymers such as polysaccharides, polypeptides, and ribonucleic acids, lignin polymers are derived from multiple types of monomeric units. However, lignin’s renowned recalcitrance is largely attributable to its racemic nature and the variety of covalent inter-unit linkages through which its aromatic monomers are linked. Indeed, unlike other biopolymers whose monomers are consistently inter-linked by a single type of covalent bond, the monomeric units in lignin are linked via non-enzymatic, combinatorial radical coupling reactions that give rise to a variety of inter-unit covalent bonds in mildly branched racemic polymers. Yet, despite the chemical complexity and stability of lignin, significant strides have been made in recent years to identify routes through which valued commodities can be derived from it. This paper discusses emerging biological and biochemical means through which degradation of lignin to aromatic monomers can lead to the derivation of commercially valuable products.

Biomass and biofuel crop effects on biodiversity and ecosystem services in the North Central US

Douglas A. Landis; Claudio Gratton; Randall D. Jackson; Katherine L. Gross; David S. Duncan; Chao Liang; Timothy D. Meehan; Bruce A. Robertson; Thomas M. Schmidt; Karen A. Stahlheber; James M. Tiedje; Benjamin P. Werling

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2017

Biomass cropping systems have the potential to alter the ecosystem services provided by agricultural landscapes. Depending on crop type and management, strategic incorporation of biomass cropping systems into existing agricultural landscapes could enhance a range of ecosystem services while mitigating some disservices. Here, we review the approaches and findings of eight years of research into the potential effects of a range of biomass cropping systems on ecosystem services in the North Central US. Our research was framed by an initial assessment of the abundance and distribution of multiple taxa (i.e., biodiversity) within candidate biomass cropping systems. The processes underpinning important ecosystem services in each system were then measured or modeled, related to biodiversity metrics, and used to explore the influence of management scenarios on biodiversity and ecosystem processes. We also used these data and models to develop a decision support system that allows stakeholders to consider tradeoffs and synergies under alternative landscape composition, configuration, and agronomic management. Perennial grass cropping systems provided the greatest potential to promote multiple ecosystem services. More diverse perennial grasslands that include forbs have the potential to increase pest suppression and pollination, decrease greenhouse gas emissions, and enhance grassland bird communities, but likely at the expense of biomass yield. Providing stakeholders and policymakers with information about the expected mix of ecosystem services supported by different biomass feedstock cropping systems in advance of their adoption offers the potential for informed choices to guide the implementation and management of future biomass-producing landscapes.

Brachypodium as an experimental system for the study of stem parenchyma biology in grasses

Jacob Krüger Jensen; Curtis Gene Wilkerson

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2017

Stem parenchyma is a major cell type that serves key metabolic functions for the plant especially in large grasses, such as sugarcane and sweet sorghum, where it serves to store sucrose or other products of photosynthesis. It is therefore desirable to understand the metabolism of this cell type as well as the mechanisms by which it provides its function for the rest of the plant. Ultimately, this information can be used to selectively manipulate this cell type in a controlled manner to achieve crop improvement. In this study, we show that Brachypodium distachyon is a useful model system for stem pith parenchyma biology. Brachypodium can be grown under condition where it resembles the growth patterns of important crops in that it produces large amounts of stem material with the lower leaves senescing and with significant stores of photosynthate located in the stem parenchyma cell types. We further characterize stem plastid morphology as a function of tissue types, as this organelle is central for a number of metabolic pathways, and quantify gene expression for the four main classes of starch biosynthetic genes. Notably, we find several of these genes differentially regulated between stem and leaf. These studies show, consistent with other grasses, that the stem functions as a specialized storage compartment in Brachypodium.

Bumble bee colony growth and reproduction depend on local flower dominance and natural habitat area in the surrounding landscape

Brian J. Spiesman; Ashley Bennett; Rufus Isaacs; Claudio Gratton

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2017

Conservation measures for bees often focus on increasing the diversity and abundance of floral resources. But it has not been clear if observed benefits of floral enhancements result from greater population growth, which is critical for the long-term success of conservation, or from mobile foragers aggregating in high-resource locations. Experimental evidence is only beginning to emerge in favor of the former mechanism and it is not well-established how different aspects of floral resources affect population growth. For example, bumble bee colonies may benefit from greater overall floral abundance, richness, or relative dominance of resource species. Because bumble bees are highly mobile, resource variability in the surrounding landscape is also important for colonies and may mediate local-scale effects. We experimentally assessed the growth and reproduction of bumble bee colonies (Bombus impatiens) deployed in grasslands in different local- and landscape-scale resource environments. We found that floral dominance, rather than the overall abundance or richness of floral resources, was the most important local factor for colony growth and reproduction. This may reflect more efficient foraging on a few numerically dominant and abundant resource species. Local- and landscape-scale predictor variables had interacting effects on colony growth and reproduction, suggesting that foraging distance depends on where in the landscape efficiently used resources are located. Our results provide further evidence that conservation strategies aimed at enhancing floral resources can increase bumble bee population growth. However, the most effective form of floral enhancement may vary among bee species.

Cellulosic feedstock production on Conservation Reserve Program land: potential yields and environmental effects

Stephen D. LeDuc; Xuesong Zhang; Christopher M. Clark; César Izaurralde

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2017

Producing biofuel feedstocks on current agricultural land raises questions of a “food-vs-fuel” tradeoff. The use of current or former Conservation Reserve Program (CRP) land offers an alternative; yet the volumes of ethanol that could be produced and the potential environmental impacts of such a policy are unclear. Here, we applied the Environmental Policy Integrated Climate (EPIC) model to a U.S. Department of Agriculture database of over 200,000 CRP polygons in Iowa, USA, as a case study. We simulated yields and environmental impacts of growing three cellulosic biofuel feedstocks on CRP land: (i) an Alamo-variety switchgrass (Panicum virgatum L.); (ii) a generalized mixture of C4 and C3 grasses; (iii) and no-till corn (Zea mays L.) with residue removal. We simulated yields, soil erosion, and soil carbon (C) and nitrogen (N) stocks and fluxes. We found that although no-till corn with residue removal produced approximately 2.6-4.4 times more ethanol per area compared to switchgrass and the grass mixture, it also led to 3.9-4.5 times more erosion, 4.4-5.2 times more cumulative N loss, and a 10% reduction in total soil carbon as opposed to a 6-11% increase. Switchgrass resulted in the best environmental outcomes even when expressed on a per liter ethanol basis. Our results suggest planting no-till corn with residue removal should only be done on low slope soils to minimize environmental concerns. Overall, this analysis provides additional information to policy makers on the potential outcome and effects of producing biofuel feedstocks on current or former conservation lands. This article is protected by copyright. All rights reserved.

Cover crop root contributions to soil carbon in a no-till corn bioenergy cropping system

Emily E. Austin; Kyle Wickings; Marshall D. McDaniel; Philip Robertson; Stuart Grandy

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2017

Deciphering the role of the phenylpropanoid metabolism in the tolerance of Capsicum annuum L. to Verticillium dahliae Kleb.

Marta Novo; Cristina Silvar; Fuencisla Merino; Teresa Martínez-Cortés; Fachuang Lu; John Ralph; Federico Pomar

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2017

Verticillium dahliae is an economically relevant soilborne pathogen that causes vascular wilt in several crops, including pepper (Capsicum annuum). Fungal infection is usually visualized as a vascular browning, likely due to the onset of phenylpropanoid metabolism, which also seems to play a crucial role in the tolerance of some pepper varieties. In the current work, the potential function of distinct phenylpropanoid derivatives (suberin, lignin and phenolic compounds) in the pepper tolerance response against V. dahliae, was investigated. Histochemical and biochemical analyses ruled out suberin as a key player in the pepper-fungus interaction. However, changes observed in lignin composition and higher deposition of bound phenolics in infected stems seemed to contribute to the reinforcement of cell walls and the impairment of V. dahliae colonization. Most importantly, this is the first time that the accumulation of the hydroxycinnamic acid amide N-feruloyltyramine was reported in pepper stems in response to a vascular fungus. Fungitoxic activity for that hydroxycinnamate-tyramine conjugate was demonstrated as well.

Degradation of lignin β-aryl ether units in Arabidopsis thaliana expressing LigD, LigF and LigG from Sphingomonas paucimobilis SYK-6

Ewelina Mnich; Ruben Vanholme; Paula Oyarce; Sarah Liu; Fachuang Lu; Geert Goeminne; Bodil Jørgensen; Mohammed S. Motawie; Wout Boerjan; John Ralph; Peter Ulvskov; Birger L. Møller; Nanna Bjarnholt; Jesper Harholt

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2017

Lignin is a major polymer in the secondary plant cell wall and composed of hydrophobic interlinked hydroxyphenylpropanoid units. The presence of lignin hampers conversion of plant biomass into biofuels; plants with modified lignin are therefore being investigated for increased digestibility. The bacterium Sphingomonas paucimobilis produces lignin-degrading enzymes including LigD, LigF and LigG involved in cleaving the most abundant lignin interunit linkage, the beta-aryl ether bond. In this study, we expressed the LigD, LigF and LigG (LigDFG) genes in Arabidopsis thaliana to introduce postlignification modifications into the lignin structure. The three enzymes were targeted to the secretory pathway. Phenolic metabolite profiling and 2D HSQC NMR of the transgenic lines showed an increase in oxidized guaiacyl and syringyl units without concomitant increase in oxidized beta-aryl ether units, showing lignin bond cleavage. Saccharification yield increased significantly in transgenic lines expressing LigDFG, showing the applicability of our approach. Additional new information on substrate specificity of the LigDFG enzymes is also provided.

Design of biofuel supply chains with variable regional depot and biorefinery locations

Rex T.L. Ng; Christos T. Maravelias

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2017

We propose a multi-period mixed-integer linear programming (MILP) model for the design and operational planning of cellulosic biofuel supply chains. Specifically, the proposed MILP model accounts for biomass selection and allocation, technology selection and capacity planning at regional depots and biorefineries. Importantly, it considers the location of regional depots and biorefineries as continuous optimization decisions. We introduce approximation and reformulation methods for the calculation of the shipments and transportation distance in order to obtain a linear model. We illustrate the applicability of the proposed methods using two medium-scale examples with realistic data.

Designing agricultural landscapes for biodiversity-based ecosystem services

Douglas A. Landis

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2017

Sustainable and resilient agricultural systems are needed to feed and fuel a growing human population. However, the current model of agricultural intensification which produces high yields has also resulted in a loss of biodiversity, ecological function, and critical ecosystem services in agricultural landscapes. A key consequence of agricultural intensification is landscape simplification, where once heterogeneous landscapes contain increasingly fewer crop and non-crop habitats. Landscape simplification exacerbates biodiversity losses which leads to reductions in ecosystem services on which agriculture depends. In recent decades, considerable research has focused on mitigating these negative impacts, primarily via management of habitats to promote biodiversity and enhance services at the local scale. While it is well known that local and landscape factors interact, modifying overall landscape structure is seldom considered due to logistical constraints. I propose that the loss of ecosystem services due to landscape simplification can only be addressed by a concerted effort to fundamentally redesign agricultural landscapes. Designing agricultural landscapes will require that scientists work with stakeholders to determine the mix of desired ecosystem services, evaluate current landscape structure in light of those goals, and implement targeted modifications to achieve them. I evaluate the current status of landscape design, ranging from fundamental ecological principles to resulting guidelines and socioeconomic tools. While research gaps remain, the time is right for ecologists to engage with other disciplines, stakeholders, and policymakers in education and advocacy to foster agricultural landscape design for sustainable and resilient biodiversity services.

Determination of glycoside hydrolase specificities during hydrolysis of plant cell walls using glycome profiling

Johnnie A. Walker; Sivakumar Pattathil; Lai F. Bergeman; Emily T. Beebe; Kai Deng; Maryam Mirzai; Trent R. Northen; Michael G. Hahn; Brian G. Fox

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2017

Glycoside hydrolases (GHs) are enzymes that hydrolyze polysaccharides into simple sugars. To better understand the specificity of enzyme hydrolysis within the complex matrix of polysaccharides found in the plant cell wall, we studied the reactions of individual enzymes using glycome profiling, where a comprehensive collection of cell wall glycan-directed monoclonal antibodies are used to detect polysaccharide epitopes remaining in the walls after enzyme treatment and quantitative nanostructure initiator mass spectrometry (oxime-NIMS) to determine soluble sugar products of their reactions.

Distribution of switchgrass (Panicum virgatum L.) aboveground biomass in response to nitrogen addition and across harvest dates

Jessica R. Miesel; Laura C. Jach-Smith; Mark J. Renz; Randall D. Jackson

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2017

Decisions about the harvest timing for switchgrass (Panicum virgatum L.) crops has important implications for economic and environmental objectives because there may be a significant trade-off between harvestable yield, bioenergy crop quality, and environmental cost or benefit. We investigated the effects of harvest timing and nitrogen (N) addition on switchgrass crops established in Wisconsin, USA to investigate the causes of biomass loss over time and to identify plant components that contribute to N loss or retention at each harvest date. We found that harvestable yield decreased over successive harvest dates, as a result of the physical loss of leaves and inflorescence biomass. Although N addition increased total aboveground biomass, it also increased the proportion of biomass occurring as leaves and infloresence. Leaf and infloresence biomass decreased over time and during harvest operations; however, this biomass became incorporated into the litter pool and increased on-site N retention. We conclude that although adding N to switchgrass is unlikely to increase harvestable yield when harvests are conducted after plant senescence, retention of high-N plant components will help maintain long-term site productivity and ecosystem function of bioenergy cropping systems, especially for sites targeted for low-input management.

Ecoinformatics (big data) for agricultural entomology: pitfalls, progress, and promise

Jay A. Rosenheim; Claudio Gratton

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2017

Ecoinformatics, as defined in this review, is the use of pre-existing, observational datasets to address questions in ecology. We provide the first review of ecoinformatics methods in agricultural entomology. Ecoinformatics methods have been used to address the full range of questions studied by agricultural entomologists, enabled by the special opportunities associated with datasets that are larger, that are more diverse, and that embrace larger spatial and temporal scales than most experimental studies. We argue that ecoinformatics research methods and traditional, experimental research methods have strengths and weaknesses that are largely complementary. We address the important interpretational challenges associated with observational datasets, highlight common pitfalls, and propose some best practices for researchers using these methods. Ecoinformatics methods hold great promise as a vehicle for capitalizing on the explosion of data emanating from farmers, researchers, and the public, as novel sampling and sensing techniques are developed and digital data sharing becomes more widespread. Expected final online publication date for the Annual Review of Entomology Volume 62 is January 7, 2017. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Effect of ethanol blending on particulate formation from premixed combustion in spark-ignition engines

Stephen Sakai; David A. Rothamer

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2017

Particulate formation due to combustion of a wide range of ethanol-gasoline blends were investigated in an internal combustion engine. The engine used for this study is a single-cylinder research engine, the architecture of which is representative of a modern spark ignited direct injected (SIDI) engine. Instead of direct injection, the engine was fueled using a premixed prevaporized (PMPV) mode, which supplied the fuel to the engine in a well-mixed, gas-phase air-fuel mixture in order to isolate physical effects of the fuel. This created a completely homogenous air-fuel mixture with no pockets of significantly differing equivalence ratio, liquid fuel droplets, or wetted surfaces, ensuring that particulate formation was due to homogenous, gas-phase combustion. The engine was operated at a fixed load and phasing so that the effects of varying equivalence ratio and ethanol content could be examined. The results in this work show that the addition of ethanol results in a consistent decrease in engine-out particulate proportional to ethanol content. Moreover, the critical equivalence ratio, the equivalence ratio at which significant sooting begins, increases in a linear fashion with ethanol addition. It was also shown that the shape of the particulate size distribution (PSD) is affected by ethanol content, with increased ethanol leading to more nucleation-mode dominated distributions.

Effect of increased fuel volatility on CDC operation in a light-duty CIDI engine

Michael A. Groendyk; David A. Rothamer

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2017

Alternative diesel fuels derived from biomass can vary significantly in volatility compared to their petroleum-derived counterparts, and their appropriate utilization is contingent on their compatibility with existing engine infrastructure. To investigate this compatibility, experiments were carried out to study the effect of fuel volatility on conventional diesel combustion (CDC) performance under a wide range of in-cylinder thermodynamic conditions at start of injection (SOI). Fuels of matched reactivity (i.e., cetane number (CN)) and varying volatility were produced by blending binary mixtures of 2,6,10-trimethyldodecane (farnesane) and 2,2,4,4,6,8,8-heptamethylnonane, octane number primary reference fuels (PRF), and cetane number secondary reference fuels (SRF). Nine fuel blends were tested in total, consisting of 3 volatility characteristics at 3 reactivity levels. Five engine operating conditions were utilized, ranging from 14.7–29 kg/m3 and 980–1120 K in-cylinder density and temperature at SOI. Testing was performed in a single-cylinder GM 1.9 L diesel engine. Only small differences in ignition delay (ID), in-cylinder pressure, and heat release rate (HRR) were observed between fuels of matched CN, regardless of their volatility. An analysis of the spray breakup and mixture formation process indicated that there were only small variations in ambient air entrainment and jet temperature between fuel blends, in agreement with the observed combustion behavior.

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