Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Controlling the Competition: Boosting Laccase/HBT-Catalyzed Cleavage of a β-O-4′ Linked Lignin Model
    Hilgers, Roelant ; Dam, Annemieke Van; Zuilhof, Han ; Vincken, Jean Paul ; Kabel, Mirjam A. - \ 2020
    ACS Catalysis 10 (2020)15. - ISSN 2155-5435 - p. 8650 - 8659.
    biocatalysis - competition - density functional theory - H-bonds - lignocellulose - mediator - reaction mechanisms
    Over the past years, laccase/mediator systems (LMS) have received a lot of attention as potential sustainable tools for biocatalytic lignin degradation. Nevertheless, it has often been reported that Cα-oxidation, rather than ether bond cleavage, is the main result of LMS treatments, which limits the overall efficiency and effectiveness. Remarkably few studies have attempted to influence this product profile and thereby enhance the effectivity of LMS-catalyzed lignin degradation. Here, we studied the influence of buffer properties on the product profile of a β-O-4′ linked lignin model dimer upon conversion by a laccase/hydroxybenzotriazole system. We show that the ratio between β-O-4′ ether cleavage and Cα-oxidation can be substantially increased by using unconventional buffer properties (i.e., highly concentrated buffers at near-neutral pH). Whereas <10% ether cleavage was obtained in conventional buffer (i.e., weak buffer at pH 4), as much as 80% ether cleavage was obtained in highly concentrated buffers at pH 6. In addition, this alteration of buffer properties was found to improve the stability of both laccase and mediator. The underlying reactions were further studied by using experimental and computational (density functional theory, DFT) approaches. Based on the outcomes, we propose detailed reaction mechanisms for the reactions underlying ether cleavage and Cα-oxidation. We propose that increasing buffer pH or increasing buffer strength enhances H-bonding between the lignin model and buffer anions, which drives the overall reaction outcome toward ether cleavage. These insights may pave the way for more efficient and effective biocatalytic lignin degradation.
    Breeding progress and preparedness for mass-scale deployment of perennial lignocellulosic biomass crops switchgrass, miscanthus, willow and poplar
    Clifton-Brown, John ; Harfouche, Antoine ; Casler, Michael D. ; Dylan Jones, Huw ; Macalpine, William J. ; Murphy-Bokern, Donal ; Smart, Lawrence B. ; Adler, Anneli ; Ashman, Chris ; Awty-Carroll, Danny ; Bastien, Catherine ; Bopper, Sebastian ; Botnari, Vasile ; Brancourt-Hulmel, Maryse ; Chen, Zhiyong ; Clark, Lindsay V. ; Cosentino, Salvatore ; Dalton, Sue ; Davey, Chris ; Dolstra, Oene ; Donnison, Iain ; Flavell, Richard ; Greef, Joerg ; Hanley, Steve ; Hastings, Astley ; Hertzberg, Magnus ; Hsu, Tsai Wen ; Huang, Lin S. ; Iurato, Antonella ; Jensen, Elaine ; Jin, Xiaoli ; Jørgensen, Uffe ; Kiesel, Andreas ; Kim, Do Soon ; Liu, Jianxiu ; McCalmont, Jon P. ; McMahon, Bernard G. ; Mos, Michal ; Robson, Paul ; Sacks, Erik J. ; Sandu, Anatolii ; Scalici, Giovanni ; Schwarz, Kai ; Scordia, Danilo ; Shafiei, Reza ; Shield, Ian ; Slavov, Gancho ; Stanton, Brian J. ; Swaminathan, Kankshita ; Trindade, Luisa M. - \ 2019
    Global change biology Bioenergy 11 (2019)1. - ISSN 1757-1693 - p. 118 - 151.
    bioenergy - feedstocks - lignocellulose - M. sacchariflorus - M. sinensis - Miscanthus - Panicum virgatum - perennial biomass crop - Populus spp. - Salix spp.

    Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output–input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed-based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass-scale deployment of PBCs.

    Targets and tools for optimizing lignocellulosic biomass quality of miscanthus
    Weijde, R.T. van der - \ 2016
    Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Luisa Trindade; Oene Dolstra. - Wageningen : Wageningen University - ISBN 9789462578388 - 231
    miscanthus - bioethanol - biomass - biofuels - lignocellulose - fuel crops - plant breeding - cell walls - cell wall components - genetic diversity - genetic variation - biomass conversion - biobased economy - miscanthus - bioethanol - biomassa - biobrandstoffen - lignocellulose - brandstofgewassen - plantenveredeling - celwanden - celwandstoffen - genetische diversiteit - genetische variatie - biomassaconversie - biobased economy

    Miscanthus is a perennial energy grass characterized by a high productivity and resource-use efficiency, making it an ideal biomass feedstock for the production of cellulosic biofuels and a wide range of other biobased value-chains. However, the large-scale commercialization of converting biomass into cellulosic biofuel is hindered by our inability to efficiently deconstruct the plant cell wall. The plant cell wall is a complex and dynamic structure and its components are extensively cross-linked into an unyielding matrix. The production of biofuel depends on the extraction, hydrolysis and fermentation of cell wall polysaccharides, which currently requires energetically and chemically intensive processing operations that negatively affect the economic viability and sustainability of the industry. To address this challenge it is envisioned that the bioenergy feedstocks can be compositionally tailored to increase the accessibility and extractability of cell wall polysaccharides, which would allow a more efficient conversion of biomass into biofuel under milder processing conditions.

    Extensive phenotypic and genetic diversity in cell wall composition and conversion efficiency was observed in different miscanthus species, including M. sinensis, M. sacchariflorus and interspecific hybrids between these two species. In multiple experiments a twofold increase in the release of fermentable sugars was observed in ‘high quality’ accessions compared to ‘low quality’ accessions. The exhaustive characterization of eight highly diverse M. sinensis genotypes revealed novel and distinct breeding targets for different bioenergy conversion routes. The key traits that contributed favourably to the conversion efficiency of biomass into biofuel were a high content of hemicellulosic polysaccharides, extensive cross-linking of hemicellulosic polysaccharides (revealed by a high content of trans-ferulic acids and a high ratio of arabinose-to-xylose), a low lignin content and extensive incorporation of para-coumaric acid into the lignin polymer.

    Lignin is widely recognized as one of the key factors conveying recalcitrance against enzymatic deconstruction of the cell wall. The incorporation of para-coumaric acid into the lignin polymer is hypothesized to make lignin more easily degradable during alkaline pretreatment, one of the most widely applied processing methods that is used to pretreat biomass prior to enzymatic hydrolysis. Previous studies have shown that reducing lignin content is often implicated in reduced resistance of plants to lodging. We hypothesize that extensively cross-linked hemicellulosic polysaccharides may fulfil a similar function in supporting cell wall structural rigidity and increasing the content of hemicellulosic polysaccharides may be a way to reduce lignin content without adversely affecting cell wall rigidity. This strategy can be used to improve biomass quality for biobased applications, as hemicellulosic polysaccharides are more easily degradable during industrial processing than lignin. Furthermore, hemicellulosic polysaccharides adhere to cellulose, which negatively affects the level of cellulose crystallinity. Crystalline cellulose is harder to degrade than its more amorphous form. Therefore the reduction of cellulose crystallinity is another mechanism through which increasing the content of hemicellulosic polysaccharides positively contributes to cell wall degradability. These results provided new insights into the traits that may be targeted to improve the quality of lignocellulose feedstocks.

    However, evaluation of complex biochemical traits for selection purposes is hindered by the fact that their accurate quantification is a costly, lengthy and laborious procedure. To overcome these limitations an accurate and high-throughput method was developed based on near-infrared spectroscopy. Through extensive calibration we developed accurate prediction models for a wide range of biomass quality characteristics, which may be readily implemented as a phenotyping tool for selection purposes.

    Additionally, progress through breeding may substantially be improved by marker-assisted selection, which will reduce the need for the evaluation of genotype performance in multi-year field trials. To this end, a biparental M. sinensis mapping population of 186 individuals was developed and genotyped using a genotyping-by-sequencing approach. A total of 564 short-sequence markers were used to construct a new M. sinensis genetic map. Cell wall composition and conversion efficiency were observed to be highly heritable and quantitatively inherited properties. This is the first genetic study in miscanthus to map quantitative trait loci (QTLs) for biomass quality properties and is a first step towards the application of marker-assisted selection for biomass quality properties.

    Through the evaluation of a diverse set of miscanthus genotypes in multiple locations we demonstrated that in addition to genotypic variation, growing conditions may have a substantial influence on cell wall composition and conversion efficiency. While further research is needed to identify which specific environmental parameters are responsible for the observed effects, these results clearly indicate that the environmental influence on biomass quality needs to be taken into account in order to match genotype, location and end-use of miscanthus as a lignocellulose feedstock. Moreover, significant genotype-by-environment interaction effects were observed for cell wall composition and conversion efficiency, indicating variation in environmental sensitivity across genotypes. Although the magnitude of the genotypic differences was small in comparison to genotype and environmental main effects, this affected the ranking of accession across environments. Stability analysis indicated some stable accessions performed relatively across diverse locations.

    In addition to trialing miscanthus in diverse locations, we also evaluated miscanthus biomass quality under drought conditions for a number of reasons: 1) drought stress is linked to a differential expression of cell wall biosynthesis genes, 2) incidence of drought events is increasing due to climate change, 3) irrigation is likely to be uneconomical during the cultivation of miscanthus and 4) miscanthus has many characteristics that make it a crop with a good potential for cultivation on marginal soils, where abiotic stresses such as drought may prevail. Drought stress was shown to result in a large reduction in cell wall and cellulose content and a substantial increase in hemicellulosic polysaccharides and cellulose conversion rates. We hypothesized that the reduction in cellulose content was due to an increase in the production of osmolytes, which are well-known for their role in plant protection against drought. The results indicated that drought stress had a positive effect on the cell wall degradability of miscanthus biomass.

    Overall the compendium of knowledge generated within the framework of this thesis provided insights into the variation in biomass quality properties in miscanthus, increased our understanding of the molecular, genetic and environmental factors influencing its conversion efficiency into biofuel and provided tools to exploit these factors to expand the use of miscanthus as a lignocellulose feedstock.

    Biorefinery of leafy biomass using green tea residue as a model material
    Zhang, C. - \ 2016
    Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): Marieke Bruins. - Wageningen : Wageningen University - ISBN 9789462576902 - 156
    biorefinery - biomass conversion - leaves - biomass - green tea - tea - alkaline pulping - pectins - lignocellulose - environmental impact - processes - plant protein - food - biobased economy - bioraffinage - biomassaconversie - bladeren - biomassa - groene thee - thee - alkalische pulpbereiding - pectinen - lignocellulose - milieueffect - processen - plantaardig eiwit - voedsel - biobased economy


    With the rapidly growing world population and improving living standards, food demand is increased with a simultaneous desire for less human impact on the environment, such that “Twice the food production at half the ecological footprint” could be the EU goal for 2050. In fact, a boost in food demand is mainly required in developing countries, where the farmlands are limited and/or they are of poor quality. Rather than improving crop-production yield, developing biorefinery technology with unused biomass, such as leaves, in developing countries may be the key to fulfil the food demand.

    Four major components, protein, pectin, lignin, and (hemi-) cellulose, account for more than 70% of the materials in leaves in almost all species. Among these components, protein and pectin can be used in food and animal feed, and they are key components for supplementing food production. However, the production and application of leaf products is limited for four reasons: unstable raw materials, complex components, rigid plant cell walls, and underdeveloped leaf logistics and economics. The limitations cause low pectin and protein yields, and low cost-efficiency in current extraction technologies, including mechanical milling, chemical extraction (acid and alkaline), solvent extraction, and ammonia protein extraction. Development of an integrated process for multiple products might be a good option for leaf biorefinery, but the compatibilities of these processes were unknown.

    The aim of this study was to develop new processes and applications that optimally utilize all components, particularly protein, of leafy biomass in the feed and/or food industry using green tea residues as a starting material. The method should also be applicable to other leafy biomass. The research started from the development of alkaline protein extraction technology as presented in Chapter 2. We found that in alkaline protein extraction, temperature, NaOH amount, and extraction time are the parameters determining protein yield, while pH and volume of extraction liquid are critical parameters for production cost. After optimization, more than 90% of leaf protein could be extracted at a cost of 102€/ton protein by single step alkaline extraction. The extracted protein nutritional value was comparable to soybean meal and this technique can be adapted to various leafy biomass. Main drawback of this technique is the overuse of alkali, generation of salts, and the destruction of key amino acids, such as lysine, during the extraction. We tried to overcome its drawbacks by developing integrated process with a recycle for chemicals.

    Chapter 3, 4, 5, and 6 refer to the integrated biorefinery. For a better design, we investigated how the alkali aided protein extraction (Chapter 3), and proved that alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, polyphenols, and organic acids can be extracted before protein. Protein extraction can then be followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin yield were both linearly correlated to protein yield, which indicated that they are likely to be the key limitation to leaf protein extraction. Based on the above findings, an integrated biorefinery that combined protein extraction with a pre-treatment was proposed. In Chapter 4, ethanol, viscozyme, and H2O2 were selected for pre-treatments targeting on the removal of polyphenols and pigments, carbohydrates, and lignin accordingly. Ethanol and viscozyme could extract their targeting components efficiently while H2O2 could bleach GTR with no lignin extracted. The best pre-treatment was the combination of viscozyme and 50% ethanol extraction, which not only reduced the use of alkali by 50%, but also improved protein content and its nutritional value. As pectin can be applied for food or chemicals, enzyme and PBS buffer were investigated for pectin extraction (Chapter 5). Both enzyme and PBS buffer extraction could not only extract high yield HG pectin (predominated by galacturonic acid) with no protein extraction, but also reduced alkali usage in subsequent protein extraction. Pectin obtained using PBS buffer could be present in its native form, which can be precipitated by 40% ethanol. Buffer is suggested to extract pectins when pectins are to be used in food. Otherwise, hydrolyzed pectin that mainly contains galacturonic acid, can be converted to other useful chemicals. For this the enzymatic methods, such as using Viscozyme® L, are recommended.

    Alkali usage was further optimized. It was found that by using potassium hydroxide, the protein extraction efficiency was similar to that using sodium hydroxide. The waste water, mainly containing potassium salts, can then be used as fertilizer. This technique is highly depending on the location of factories, which should be built close to the field. Alternatively, calcium hydroxide can be used. As calcium salts can be precipitated by CO2 and calcium hydroxide can be regenerated through burning of the precipitate, this scheme is sustainable and adaptable to most situations. However, as calcium also precipitated pectin, ployphenols, and even proteins, the protein yield is relatively low. Although a pre-treatment can improve extraction efficiency of calcium hydroxide, economic results suggested that a pre-treatment is not necessary unless the products obtained by pre-treatment have an attractive market value.

    In Chapter 7, we extend our knowledge on leaf biorefinery with some additional experiments and literature. Simplified models of leaf tissues and cell walls were proposed and used to explain the mechanism of alkaline protein extraction. The models were also used to explain other mechanisms for protein extraction; mechanical milling, steam explosion, acid, and enzyme aided extraction. The possible improvements of leaf biorefinery economics were illustrated either by reducing production cost, by e.g. using counter current extraction or ultrafiltration, or by upgrading product value by applying protein and pectin in food. The processes recommended in this thesis show an excellent prospective, in which they are applicable to other leaf biomass and suitable for small-scale production.

    Development of a lactic acid production process using lignocellulosic biomass as feedstock
    Pol, E.C. van der - \ 2016
    Wageningen University. Promotor(en): Gerrit Eggink, co-promotor(en): Ruud Weusthuis. - Wageningen : s.n. - ISBN 9789462576735 - 167
    lignocellulose - biomass - biobased chemicals - sugarcane bagasse - lactic acid - sugars - byproducts - inhibitors - pretreatment - bacillus coagulans - furfural - saccharification - fermentation - quantitative techniques - production processes - lignocellulose - biomassa - chemicaliën uit biologische grondstoffen - suikerrietbagasse - melkzuur - suikers - bijproducten - remmers - voorbehandeling - bacillus coagulans - furfural - versuikering - fermentatie - kwantitatieve technieken - productieprocessen

    The availability of crude oil is finite. Therefore, an alternative feedstock has to be found for the production of fuels and plastics. Lignocellulose is such an alternative feedstock. It is present in large quantities in agricultural waste material such as sugarcane bagasse.

    In this PhD thesis, lignocellulose is chemically and enzymatically pretreated to depolymerise sugars present in this structure. The released sugar monomers are fermented by micro-organisms to lactic acid, which is a precursor for the bioplastic PLA. In this thesis, it is shown that it is possible to produce lactic acid from lignocellulosic biomass with high yields and high productivities.

    Uncovering the abilities of Agaricus bisporus to degrade plant biomass throughout its life cycle
    Patyshakuliyeva, A. ; Post, H. ; Zhou, M. ; Jurak, E. ; Heck, A.J.R. ; Hilden, K.S. ; Kabel, M.A. ; Makela, M.R. ; Altenaar, M.A.F. ; Vries, R.P. de - \ 2015
    Environmental Microbiology 17 (2015)8. - ISSN 1462-2912 - p. 3098 - 3109.
    fungus phanerochaete-chrysosporium - ceriporiopsis-subvermispora - mannitol dehydrogenase - fomitopsis-palustris - gene-expression - button mushroom - rot fungi - acid - lignocellulose - insights
    The economically important edible basidiomycete mushroom Agaricus bisporus thrives on decaying plant material in forests and grasslands of North America and Europe. It degrades forest litter and con-tributes to global carbon recycling, depolymerizing (hemi-)cellulose and lignin in plant biomass. Relatively little is known about how A. bisporus grows in the controlled environment in commercial production facilities and utilizes its substrate. Using transcriptomics and proteomics, we showed that changes in plant biomass degradation by A. bisporus occur throughout its life cycle. Ligninolytic genes were only highly expressed during the spawning stage day 16. In contrast, (hemi-)cellulolytic genes were highly expressed at the first flush, whereas low expression was observed at the second flush. The essential role for many highly expressed plant biomass degrading genes was supported by exoproteome analysis. Our data also support a model of sequential lignocellulose degradation by wood-decaying fungi proposed in previous studies, concluding that lignin is degraded at the initial stage of growth in compost and is not modified after the spawning stage. The observed differences in gene expression involved in (hemi-)cellulose degradation between the first and second flushes could partially explain the reduction in the number of mushrooms during the second flush
    Isolation and Screening of Thermophilic Bacilli from Compost for Electrotransformation and Fermentation: Characterization of Bacillus smithii ET 138 as a New Biocatalyst
    Bosma, E.F. ; Weijer, A.H.P. van de; Daas, M.J.A. ; Oost, J. van der; Vos, W.M. de; Kranenburg, R. van - \ 2015
    Applied and Environmental Microbiology 81 (2015)5. - ISSN 0099-2240 - p. 1874 - 1883.
    genetic tool development - lactic-acid - simultaneous saccharification - clostridium-thermocellum - industrial platform - ethanol - lignocellulose - coagulans - bacteria - licheniformis
    Thermophilic bacteria are regarded as attractive production organisms for cost-efficient conversion of renewable resources to green chemicals, but their genetic accessibility is a major bottleneck in developing them into versatile platform organisms. In this study, we aimed to isolate thermophilic, facultatively anaerobic bacilli that are genetically accessible and have potential as platform organisms. From compost, we isolated 267 strains that produced acids from C5 and C6 sugars at temperatures of 55°C or 65°C. Subsequently, 44 strains that showed the highest production of acids were screened for genetic accessibility by electroporation. Two Geobacillus thermodenitrificans isolates and one Bacillus smithii isolate were found to be transformable with plasmid pNW33n. Of these, B. smithii ET 138 was the best-performing strain in laboratory-scale fermentations and was capable of producing organic acids from glucose as well as from xylose. It is an acidotolerant strain able to produce organic acids until a lower limit of approximately pH 4.5. As genetic accessibility of B. smithii had not been described previously, six other B. smithii strains from the DSMZ culture collection were tested for electroporation efficiencies, and we found the type strain DSM 4216T and strain DSM 460 to be transformable. The transformation protocol for B. smithii isolate ET 138 was optimized to obtain approximately 5 × 103 colonies per µg plasmid pNW33n. Genetic accessibility combined with robust acid production capacities on C5 and C6 sugars at a relatively broad pH range make B. smithii ET 138 an attractive biocatalyst for the production of lactic acid and potentially other green chemicals
    Factors Impeding Enzymatic Wheat Gluten Hydrolysis at High Solid Concentrations
    Hardt, N.A. ; Janssen, A.E.M. ; Boom, R.M. ; Goot, A.J. van der - \ 2014
    Biotechnology and Bioengineering 111 (2014)7. - ISSN 0006-3592 - p. 1304 - 1312.
    functional-properties - water activity - plastein synthesis - biomass - lignocellulose - inhibition - proteins - softwood
    Enzymatic wheat gluten hydrolysis at high solid concentrations is advantageous from an environmental and economic point of view. However, increased wheat gluten concentrations result in a concentration effect with a decreased hydrolysis rate at constant enzyme-to-substrate ratios and a decreased maximum attainable degree of hydrolysis (DH%). We here identified the underlying factors causing the concentration effect. Wheat gluten was hydrolyzed at solid concentrations from 4.4% to 70%. The decreased hydrolysis rate was present at all solid concentrations and at any time of the reaction. Mass transfer limitations, enzyme inhibition and water activity were shown to not cause this hydrolysis rate limitation up to 50% solids. However, the hydrolysis rate limitation can be, at least partly, explained by a second-order enzyme inactivation process. Furthermore, mass transfer impeded the hydrolysis above 60% solids. Addition of enzyme after 24 h at high solid concentrations scarcely increased the DH%, suggesting that the maximum attainable DH% decreases at high solid concentrations. Reduced enzyme activities caused by low water activities can explain this DH% limitation. Finally, a possible influence of the plastein reaction on the DH% limitation is discussed.
    Complementary symbiont contributions to plant decomposition in a fungus-farming termite
    Poulsen, M. ; Hu, H. ; Li, C. ; Chen, Z. ; Xu, L. ; Otani, S. ; Nygaard, S. ; Nobre, T. ; Klaubauf, S. ; Schindler, P.M. ; Hauser, F. ; Pan, H. ; Yang, Z. ; Sonnenberg, A.S.M. ; Beer, W. de; Zhang, Y. ; Wingfield, M.J. ; Grimmelikhuijzen, C.J.P. ; Vries, R.P. de; Korb, J. ; Aanen, D.K. ; Wang, J. ; Boomsma, J.J. ; Zhang, G. - \ 2014
    Proceedings of the National Academy of Sciences of the United States of America 111 (2014)40. - ISSN 0027-8424 - p. 14500 - 14505.
    growing termites - bacterial community - gut microbiota - markov-models - genomes - termitomyces - evolution - tool - macrotermitinae - lignocellulose
    Termites normally rely on gut symbionts to decompose organic matter but the Macrotermitinae domesticated Termitomyces fungi to produce their own food. This transition was accompanied by a shift in the composition of the gut microbiota, but the complementary roles of these bacteria in the symbiosis have remained enigmatic. We obtained high-quality annotated draft genomes of the termite Macrotermes natalensis, its Termitomyces symbiont, and gut metagenomes from workers, soldiers, and a queen. We show that members from 111 of the 128 known glycoside hydrolase families are represented in the symbiosis, that Termitomyces has the genomic capacity to handle complex carbohydrates, and that worker gut microbes primarily contribute enzymes for final digestion of oligosaccharides. This apparent division of labor is consistent with the Macrotermes gut microbes being most important during the second passage of comb material through the termite gut, after a first gut passage where the crude plant substrate is inoculated with Termitomyces asexual spores so that initial fungal growth and polysaccharide decomposition can proceed with high efficiency. Complex conversion of biomass in termite mounds thus appears to be mainly accomplished by complementary cooperation between a domesticated fungal monoculture and a specialized bacterial community. In sharp contrast, the gut microbiota of the queen had highly reduced plant decomposition potential, suggesting that mature reproductives digest fungal material provided by workers rather than plant substrate.
    Synergistic action of enzyme preparations towards recalcitrant corn silage polysaccharides
    Neumüller, K.G. ; Streekstra, H. ; Schols, H.A. ; Gruppen, H. - \ 2014
    Biomass and Bioenergy 60 (2014). - ISSN 0961-9534 - p. 88 - 97.
    talaromyces-emersonii - wheat-straw - hydrolysis - pretreatment - ethanol - plant - lignocellulose - fermentation - efficiency - conversion
    Corn silage, its water unextractable solids (WUS) and enzyme recalcitrant solids (ErCS) and an industrial corn silage-based anaerobic fermentation residue (AFR) represent corn substrates with different levels of recalcitrance. Compositional analysis reveals different levels of arabinoxylan substitution for WUS, ErCS and AFR, being most pronounced regarding acetic acid, glucuronic acid- and arabinose content. By screening for enzymatic degradation of WUS, ErCS and AFR, enzyme preparations exhibiting high conversion rates were identified. Furthermore significant synergistic effects were detected by blending Aspergillus niger/Talaromyces emersonii culture filtrates with various enzymes. These findings clearly highlight a necessity for a combinatorial use of enzyme preparations towards substrates with high recalcitrance characteristics to reach high degrees of degradation. Enzyme blends were identified, outperforming the individual commercial preparations. These enzyme preparations provide a basis for new, designed enzyme mixtures for corn polysaccharide degradation as a source of necessary, accessory enzyme activities.
    Pretreatment of lignocellulose for biotechnological production of lactic acid
    Harmsen, P.F.H. ; Lips, S.J.J. ; Bakker, R.R.C. - \ 2013
    Wageningen UR FBR (Rapport / Wageningen UR Food & Biobased Research 1384, public version) - ISBN 9789461736079 - 104
    voorbehandeling - biomassaconversie - lignocellulose - melkzuur - bioproceskunde - technologie - suikerriet - kosten - kostenanalyse - biobased economy - pretreatment - biomass conversion - lignocellulose - lactic acid - bioprocess engineering - technology - sugarcane - costs - cost analysis - biobased economy
    The breakdown of biomass in pretreatment facilitates enzymatic hydrolysis by disrupting cell wall structures, driving lignin into solution or modification of the lignin structure, and reducing cellulose crystallinity and chain length, while preventing hydrolysis of cellulose. In an ideal situation the pretreatment leads to high yields of fermentable sugars with a limited formation of degradation products that inhibit enzymatic hydrolysis and fermentation to lactic acid, while remaining cost effective. This review deals with these challenges by providing information on available pretreatment technologies in general (chapter 3), and more specific on pretreatment of the model feedstock sugarcane bagasse (chapter 4). Techno economic studies are described in chapter 5 with the NREL study from 2011 as benchmark. This review starts with characteristics of lignocellulosic biomass in relation to compostion and formation of inhibitors.
    Lignin as a renewable aromatic resource for the chemical industry
    Gosselink, R.J.A. - \ 2011
    Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): G. Gellerstedt; Jan van Dam. - [S.l.] : S.n. - ISBN 9789461731005 - 191
    vervangbare hulpbronnen - lignine - lignocellulose - lignocellulosehoudend afval - pulp- en papierwarenindustrie - chemicaliën uit biologische grondstoffen - chemie op basis van biologische grondstoffen - renewable resources - lignin - lignocellulose - lignocellulosic wastes - pulp and paper industry - biobased chemicals - biobased chemistry

    Valorization of lignin plays a key role in the further development of lignocellulosic biorefinery processes for biofuels and biobased materials production. Today’s increased demand for alternatives to fossil carbon-based products expands the interest and the need to create added value to the unconverted lignin fraction. The aim of the research was to study the potential of lignin to become a renewable aromatic resource for the chemical industry. Lignin can be considered as an abundantly available and cheap raw material for the manufacturing of an array of products. Development of applications needs to go hand in hand with the anticipated increased production of technical lignins derived from the pulp and paper industry and the emerging lignocellulosic biorefinery industry. Two promising lignin applications are studied in this thesis:

    1) the use of lignin in wood adhesives

    2) the use of lignin for the production of aromatic chemicals

    PCA modeling was performed aimed at the prediction of the application potential of different technical lignins for wood adhesive production. The lignins and their fractions could be classified in different clusters based on their structure dependent properties. Lignins exhibiting sufficient reactive sites, medium molar mass and low level of impurities are most promising candidates for the development of lignin based wood adhesives. Both lignin reactivity and formaldehyde-free crosslinking agents are needed to develop emission-free adhesives. Periodate oxidation was studied as method to improve the lignin reactivity. Alternatives to formaldehyde- based glues are under investigation and a combination of lignin and furans might be an interesting concept to develop renewable adhesives.

    In this research a reliable SEC methodology was developed for the analysis of the molar mass distribution of a wide range of different lignins. The major drawback of this method is that the molar masses are calculated on a relative basis to sulfonated polystyrenes. Using MALDI-TOF-MS and prior fractionation of lignin did not solve all problems associated with the determination of the absolute molar mass of lignin.

    Supercritical depolymerisation of lignin using a carbon dioxide/acetone/water fluid resulted in a depolymerised lignin oil. In this oil some monomeric compounds are present in relatively high amounts up to 3.6% (based on dry lignin). These products maybe further isolated by downstream processing to obtain purified fine chemicals. For continuous operation of this supercritical process, the formation of char should be further limited.

    The results presented in this thesis are expected to contribute - together with the many on-going activities worldwide - to the increased commercial utilisation of lignin in the future. Moreover, the obtained results contribute to the increasing knowledge on lignin analysis, chemistry and reactivity.

    Uit elkaar geplukt is stro goud waard
    Harmsen, P.F.H. - \ 2010
    Kennis Online 7 (2010)dec. - p. 9 - 9.
    stro - maïs - lignocellulose - biobrandstoffen - biobased economy - bioethanol - biomassaconversie - straw - maize - lignocellulose - biofuels - biobased economy - bioethanol - biomass conversion
    Het onderzoek van Paulien Harmsen van het instituut Food & Biobased Research laat zien dat er meer mogelijk is met stro.
    Bioraffinage : naar een optimale verwaarding van biomassa
    Annevelink, E. ; Harmsen, P.F.H. - \ 2010
    Wageningen : Wageningen UR - Food & Biobased Research (Groene Grondstoffen 10) - ISBN 9789085857617 - 42
    chemische industrie - vervangbare hulpbronnen - nederland - biomassa - biomassa productie - lignocellulose - biobased economy - bioraffinage - productieprocessen - biomassaconversie - aquatische biomassa - chemical industry - renewable resources - netherlands - biomass - biomass production - lignocellulose - biobased economy - biorefinery - production processes - biomass conversion - aquatic biomass
    Dit boekje is geschreven met als doel bioraffinage meer bekendheid te geven. In hoofdstuk 1 is de Biobased Economy beschreven en de sleutelrol die bioraffinage daarin speelt, met een focus op Nederland. Bioraffinage is een zeer brede term en een classificatiesysteem is noodzakelijk; dit is beschreven in hoofdstuk 2. In de hoofdstukken 3 en 4 wordt vervolgens dieper ingegaan op de grondstof voor bioraffinage, de biomassa, en de verschillende conversiemethoden die kunnen worden toegepast voor de verwerking van biomassa tot waardevolle producten. Vervolgens wordt in de hoofdstukken 5 t/m 7 een aantal voorbeelden van bioraffinage beschreven. Dit boekje wordt afgesloten met een aantal aspecten die van belang zijn voor de verdere ontwikkeling van bioraffinage in de toekomst.
    Literature review of physical and chemical pretreatment processes for lignocellulosic biomass
    Harmsen, P.F.H. ; Huijgen, W. ; Bermudez, L. ; Bakker, R. - \ 2010
    Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR, Food & Biobased Research 1184) - ISBN 9789085857570 - 54
    literatuuroverzichten - lignocellulose - biomassa - voorbehandeling - bio-energie - biomassaconversie - biobased economy - literature reviews - lignocellulose - biomass - pretreatment - bioenergy - biomass conversion - biobased economy
    Different pretreatment technologies published in public literature are described in terms of the mechanisms involved, advantages and disadvantages, and economic assessment. Pretreatment technologies for lignocellulosic biomass include biological, mechanical, chemical methods and various combinations thereof. The choice of the optimum pretreatment process depends very much on the objective of the biomass pretreatment, its economic assessment and environmental impact. Only a small number of pretreatment methods has been reported as being potentially cost-effective thus far. These include steam explosion, liquid hot water, concentrated acid hydrolysis and dilute acid pretreatments.
    Biobutanol : butanol from cellulosic biomass
    Bakker, R.R. ; Lopez Contreras, A.M. ; Claassen, P.A.M. ; Merck, K.B. ; Willemsen, J.H.A. ; Mozaffarian, H. ; Uil, H. den; Pels, J. ; Reith, H. - \ 2010
    bio-energie - cellulose - fermentatie - butanol - clostridium - lignocellulose - biomassa - biobased economy - biobrandstoffen - bioenergy - cellulose - fermentation - butanol - clostridium - lignocellulose - biomass - biobased economy - biofuels
    Poster met onderzoeksinformatie over de vebetering van het ABE (aceton, butanol, ethanol) fermentatieproces. Het doel van dit onderzoek is om de productie van biobutanol uit biomassa dat cellulose bevat, rendabel te maken.
    Industrial development : biofuels for transportation
    Bakker, Rob - \ 2009
    rice straw - lignocellulose - transport - diesel oil - biobased economy - biofuels - bioethanol - future
    Lignocellulosic ethanol in Brazil : technical assessment of 1st and 2nd generation sugarcane ethanol in a Brazilian setting
    Stojanovic, M. ; Bakker, R.R.C. - \ 2009
    Wageningen : Agrotechnology and Food Innovations - 18
    suikerriet - ethanol - lignocellulose - sucrose - fermentatie - technologie - brazilië - bioethanol - biobrandstoffen - sugarcane - ethanol - lignocellulose - sucrose - fermentation - technology - brazil - bioethanol - biofuels
    Brazil is currently the largest ethanol-biofuel producer worldwide. Ethanol is produced by fermenting the sucrose part of the sugarcane that contains only one third of the sugarcane energy. The rest of the plant is burned to produce energy to run the process and to generate electricity that is sold to the public grid, making the process a net energy producer. This paper evaluates current technology from an energy efficiency point of view and quantifies additional benefits from extra energy generated in during sugarcane processing.
    Bioethanol uit lignocellulose
    Bakker, R.R.C. ; Bos, H.L. - \ 2009
    bio-energie - lignocellulose - bioethanol - biobrandstoffen - biobased economy - bioenergy - lignocellulose - bioethanol - biofuels - biobased economy
    Deze info sheet geeft een overzicht van ontwikkelingen op het gebied van productie van bioethanol, een hernieuwbare transportbrandstof, uit lignocellulose. Lignocellulose is een verzamelnaam voor alle vezelhoudende biomassa waaronder zowel houtgewassen, grassen als reststromen vallen.
    Modelling ethanol production from cellulose: separate hydrolysis and fermentation versus simultaneous saccharification and fermentation
    Drissen, R.E.T. ; Maas, R.H.W. ; Tramper, J. ; Beeftink, H.H. - \ 2009
    Biocatalysis and Biotransformation 27 (2009)1. - ISSN 1024-2422 - p. 27 - 35.
    enzymatic-hydrolysis - lignocellulose - biomass - conversion - softwood - technology - inhibition - substrate - economics
    In ethanol production from cellulose, enzymatic hydrolysis, and fermentative conversion may be performed sequentially (separate hydrolysis and fermentation, SHF) or in a single reaction vessel (simultaneous saccharification and fermentation, SSF). Opting for either is essentially a trade-off between optimal temperatures and inhibitory glucose concentrations on the one hand (SHF) vs. sub-optimal temperatures and ethanol-inhibited cellulolysis on the other (SSF). Although the impact of ethanol on cellobiose hydrolysis was found to be negligible, formation of glucose and cellobiose from cellulose were found to be significantly inhibited by ethanol. A previous model for the kinetics of enzymatic cellulose hydrolysis was, therefore, extended with enzyme inhibition by ethanol, thus allowing a rational evaluation of SSF and SHF. The model predicted SSF processing to be superior. The superiority of SSF over SHF (separate hydrolysis and fermentation) was confirmed experimentally, both with respect to ethanol yield on glucose (0.41 g g-1 for SSF vs. 0.35 g g-1 for SHF) and ethanol production rate, being 30% higher for an SSF type process. High conversion rates were found to be difficult to achieve since at a conversion rate of 52% in a SSF process the reaction rate dropped to 5% of its initial value. The model, extended with the impact of ethanol on the cellulase complex proved to predict reaction progress accurately.
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