Lignin-based polymers and nanomaterials Grossman, Adam; Vermerris, Wilfred
Current opinion in biotechnology,
April 2019, 2019-04-00, 20190401, 2019-04-01, Letnik:
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Approximately 50 million tons of lignin are currently produced annually as a by-product of the pulp- and paper industry, and this amount is likely to double in the future with the ...anticipated production of renewable fuels and chemicals from lignocellulosic biomass, as a sustainable alternative to petroleum. The latter process can be expedited by valorizing lignin, which entails making products from lignin that generate additional revenues for biorefineries so that the production of biofuels becomes more competitive with gasoline. Industrially produced lignin is considered a low-value material that is used as a boiler fuel to generate heat and electricity, and as an ingredient of adhesives, cement, and drilling fluids for underwater oil wells. The aromatic nature of lignin, its ability to participate in radical-mediated cross-linking reactions, the many functional groups available for derivatization or chemical reactions, and its amenability to existing procedures for making thermoplastics, make it attractive as an additive to polymers to enhance UV-tolerance and/or other physico-chemical properties. Lignin can also be used as the basis for various nanomaterials, either per se or in combination with other polymers. This review summarizes recent developments in the synthesis of lignin-containing polymers and nanomaterials, whereby inherent variation in lignin subunit composition and structure, as a function of plant species and lignin extraction method, offer unique opportunities for fine-tuning material properties (e.g. tensile strength, hardness, elasticity) to match specific applications.
How does the consumption of red wine reduce heart disease? How does a plant battle an invading fungus using physical and chemical defense mechanisms? How are tannins used in leather production ...synthesized? These are just a few examples that illustrate the chemical diversity and use of phenolic compounds, the topic of ‘Phenolic Compound Biochemistry’. This book is written for researchers, instructors, advanced undergraduate students and beginning graduate students in the life sciences who wish to become more familiar with these and many other intriguing aspects of phenolic compounds. Topics covered include nomenclature, chemical properties, biosynthesis, including an up-to-date overview of the genetics controlling phenolic metabolism, isolation and characterization of phenolic compounds, phenolics used in plant defense, and the impact of phenolics on human health. The book is written in an accessible style, and assumes only basic knowledge of organic chemistry, biochemistry and cell physiology. More than 300 chemical structures and reaction schemes illustrate the text. The Authors Wilfred Vermerris is Associate Professor of Agronomy at the University of Florida Genetics Institute in Gainesville, FL. His research focuses on the genetic control of phenolic compounds that impact agro-industrial processing of crop plants. Ralph Nicholson is Professor of Botany and Plant Pathology at Purdue University in West Lafayette, IN. He is an expert on phenolic compounds involved in the plant’s defense against pathogenic fungi and bacteria.
Bioenergy crops currently provide the only source of alternative energy with the potential to reduce the use of fossil transportation fuels in a way that is compatible with existing engine ...technology, including in developing countries. Even though bioenergy research is currently receiving considerable attention, many of the concepts are not new, but rather build on intense research efforts from 30 years ago. A major difference with that era is the availability of genomics tools that have the potential to accelerate crop improvement significantly. This review is focused on maize, sorghum and sugarcane as representatives of bioenergy grasses that produce sugar and/or lignocellulosic biomass. Examples of how genetic mapping, forward and reverse genetics, high-throughput expression profiling and comparative genomics can be used to unravel and improve bioenergy traits will be presented.
Bioenergy crops currently provide the only source of alternative energy with the potential to reduce the use of fossil transportation fuels in a way that is compatible with existing engine ...technology, including in developing countries. Even though bioenergy research is currently receiving considerable attention, many of the concepts are not new, but rather build on intense research efforts from 30 years ago. A major difference with that era is the availability of genomics tools that have the potential to accelerate crop improvement significantly. This review is focused on maize, sorghum and sugarcane as representatives of bioenergy grasses that produce sugar and/or lignocellulosic biomass. Examples of how genetic mapping, forward and reverse genetics, high-throughput expression profiling and comparative genomics can be used to unravel and improve bioenergy traits will be presented.
Genetic linkage maps based on single nucleotide polymorphisms (SNPs) represent an essential tool for a variety of genomic analyses. Today, next-generation sequencing (NGS) enables rapid genotyping of ...different mapping populations based on thousands of SNPs and the construction of highly saturated linkage maps. Nevertheless, missing data in the genotyping of the parental lines creates a bottleneck that determines the number of SNPs that can be used for the linkage map. As a proof of concept, a highly saturated genetic linkage map was constructed using the imputed genotypic data of a recombinant inbred line (RIL) population and the limited genotypic information of its parental lines. Two ABH genotype files were created from a pseudo-parental genotypic data set that includes all the SNPs present in the RIL population. In the first ABH file pseudo-parental 1 was considered parental A, while in the second pseudo-parental 1 was considered parental B. These two duplicate ABH genotype files were merged by chromosome and subjected to linkage map analysis. Since the ABH data were duplicated, two mirrored linkage groups were generated per chromosome. The correct linkage map was identified and selected based on the partial genotypic data of the parental lines. This strategy was effective for constructing a highly saturated linkage map of 33,421 SNPs based on the genotyping of 205 RILs and a limited number of 100 SNPs present in the parental lines. This strategy enables the use of all the NGS SNP data obtained from a low-coverage sequencing experiment in the mapping population.
Modern medicine has relied heavily on the availability of effective antibiotics to manage infections and enable invasive surgery. With the emergence of antibiotic-resistant bacteria, novel approaches ...are necessary to prevent the formation of biofilms on sensitive surfaces such as medical implants. Advances in nanotechnology have resulted in novel materials and the ability to create novel surface topographies. This review article provides an overview of advances in the fabrication of antimicrobial nanomaterials that are derived from biological polymers or that rely on the incorporation of natural compounds with antimicrobial activity in nanofibers made from synthetic materials. The availability of these novel materials will contribute to ensuring that the current level of medical care can be maintained as more bacteria are expected to develop resistance against existing antibiotics.
The biotrophic fungus Ustilago maydis causes smut disease in maize with characteristic tumor formation and anthocyanin induction. Here, we show that anthocyanin biosynthesis is induced by the ...virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with maize protein kinase ZmTTK1. Tin2 masks a ubiquitin-proteasome degradation motif in ZmTTK1, thus stabilizing the active kinase. Active ZmTTK1 controls activation of genes in the anthocyanin biosynthesis pathway. Without Tin2, enhanced lignin biosynthesis is observed in infected tissue and vascular bundles show strong lignification. This is presumably limiting access of fungal hyphae to nutrients needed for massive proliferation. Consistent with this assertion, we observe that maize brown midrib mutants affected in lignin biosynthesis are hypersensitive to U. maydis infection. We speculate that Tin2 rewires metabolites into the anthocyanin pathway to lower their availability for other defense responses. DOI: http://dx.doi.org/10.7554/eLife.01355.001.
•All sweet sorghums are >3m tall. Is this a prerequisite for sugar accumulation?•Height in sorghum is controlled by four Dw loci that act in an additive fashion.•Crossing short inbred lines with ...complementary dw genotypes results in tall offspring.•In the case of sweet sorghum, this would require short, sweet inbred parents.•This study shows that sugar accumulation can occur in short plants.
Sweet sorghum (Sorghum bicolor (L.) Moench) is a tall, seed-propagated C4 grass with stems that contain saccharine juice. The sugars in the juice can be easily extracted with a press, which generates large amounts of bagasse. Sweet sorghum has potential as a multi-purpose crop whereby depending on the available infrastructure and market demands, all fermentable sugars from juice and biomass can be converted to renewable fuels and chemicals, or the juice can be processed to syrup, fuels, or chemicals, while the bagasse is either burned or used as fodder. Large-scale industrial production of sweet sorghum requires large amounts of seed, but due to their height, sweet sorghums are not compatible with existing combine harvesters. In addition, grain yield is often limited. The availability of hybrid seed that can be produced on short seed parents would enable combine harvesting and offer greater seed yield. This requires the availability of short, sweet inbred lines. All known sweet sorghums, however, are tall, and prior research identified a positive correlation between height and sugar accumulation. Since the physiological mechanisms underlying sugar accumulation in sweet sorghum are not well understood, it is unknown whether the apparent association between sugar accumulation in the stem and plant height is the result of selection, or dictated by physiological or genetic constraints. Three experiments were conducted to examine this relationship. First, the role of shading on sugar accumulation was examined in breeding populations with contrasting heights. Second, the sugar concentration was compared between short plants harboring the unstable dwarf3 (dw3) allele and their tall Dw3 revertants. Third, tall photoperiod-sensitive lines were compared with their matching short, photoperiod-insensitive lines. The results from these three experiments indicated that high sugar concentration in sweet sorghum is not conditional on the plants being tall, making the development of short, sweet inbred lines feasible. This information will also significantly benefit studies aimed at identifying QTL for sugar yield in sweet sorghum.
Summary
Sugarcane is a prime bioethanol feedstock. Currently, sugarcane ethanol is produced through fermentation of the sucrose, which can easily be extracted from stem internodes. Processes for ...production of biofuels from the abundant lignocellulosic sugarcane residues will boost the ethanol output from sugarcane per land area. However, unlocking the vast amount of chemical energy stored in plant cell walls remains expensive primarily because of the intrinsic recalcitrance of lignocellulosic biomass. We report here the successful reduction in lignification in sugarcane by RNA interference, despite the complex and highly polyploid genome of this interspecific hybrid. Down‐regulation of the sugarcane caffeic acid O‐methyltransferase (COMT) gene by 67% to 97% reduced the lignin content by 3.9% to 13.7%, respectively. The syringyl/guaiacyl ratio in the lignin was reduced from 1.47 in the wild type to values ranging between 1.27 and 0.79. The yields of directly fermentable glucose from lignocellulosic biomass increased up to 29% without pretreatment. After dilute acid pretreatment, the fermentable glucose yield increased up to 34%. These observations demonstrate that a moderate reduction in lignin (3.9% to 8.4%) can reduce the recalcitrance of sugarcane biomass without compromising plant performance under controlled environmental conditions.
By mimicking natural lignin degradation systems, the Fenton catalyst (Fe3+, H2O2) can effectively facilitate lignin depolymerization in supercritical ethanol (7 MPa, 250 °C) to give organic oils that ...consist of mono‐ and oligomeric aromatics, phenols, dicarboxylic acids, and their derivatives in yields up to (66.0±8.5) %. The thermal properties, functional groups, and surface chemistry of lignin before and after Fenton treatment were examined by thermogravimetric analysis, pyrolysis–gas chromatography–mass spectrometry, 31P NMR spectroscopy, and X‐ray photoelectron spectroscopy. The results suggest that the Fenton catalyst facilitates lignin depolymerization through cleavage of β‐ether bonds between lignin residues. The formation of a lignin–iron chelating complex effectively depresses lignin recondensation; thus minimizing charcoal formation and enhancing the yield of liquid products.
Stripped back: Fenton catalyst (Fe3+, H2O2) effectively facilitates lignin depolymerization in supercritical ethanol to give liquid products in high yield. The results also support the formation of a lignin–iron chelating complex as an intermediate stabilizer that enhances the yield of the liquid products.
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