Plant Cell Walls: Improved Resources for Biofuels and Value‐Added Products through Genetic Engineering

Abstract

To mitigate fossil‐fuel shortages and the environmental impact of excess fossil‐fuel consumption, bioconversion of biomass into biofuels has emerged as a clean and sustainable alternative. During the past decade, a significant amount of progress has been made in understanding and improving the production of second‐generation biofuels from lignocellulosic biomass. While some challenges still need to be overcome, some of advancements led to the development of improved feedstocks to boot sugar release and incorporate functional groups into lignins to support the production of high‐value‐added by‐products.

Key Concepts

  • Plants sequester CO2 and sunlight energy in their cell walls.
  • The largest resource of sugars is stored in plant cell walls.
  • Plant cell walls can be biologically converted into biofuels.
  • Processes of plant cell walls into biofuels and value‐added products need optimisation.
  • Every cell‐wall components need to be valorised: ‘No waste policy’.
  • Plants can be engineered to optimise cell‐wall conversion efficiency.

Keywords: lignocellulosic biomass; recalcitrance; renewable energy; lignin valorisation; biofuel; plant cell walls; polysaccharides; feedstocks; genetic engineering

Figure 1. Structure and composition of lignocellulose. The main component of lignocellulose is cellulose, a β(1–4)‐linked chain of glucose molecules. Hydrogen bonds between different layers of the polysaccharides contribute to the resistance of crystalline cellulose to degradation. Hemicellulose, the second most abundant component of lignocellulose, is composed of various pentoses and hexoses such as glucose, xylose, arabinose, galactose and mannose. Lignin is composed of three major phenolic components, namely p‐coumaryl alcohol (H), coniferyl alcohol (G), and sinapyl alcohol (S). Lignin is synthesised by random polymerisation of these monomers and their ratio within the polymer varies among different plants, wood tissues, and cell wall layers. Pectin is not typically found in secondary cell walls but may affect how secondary walls are deposited. Cellulose, hemicellulose, and lignin form structures called microfibrils, which are organised into macrofibrils that are load‐bearing in the plant cell wall. Reprinted by permission from Macmillan Publishers Ltd: Nature (Rubin EM (2008) Genomics of cellulosic biofuels. Nature 454: 841–845.), copyright (2008).
Figure 2. Schematic diagram of the conversion of feedstocks to sugars and lignin for biofuel fermentation and bioproducts, respectively. (a) Plant biomass sequesters solar energy and is used as feedstocks. Various fast‐growing and low‐maintenance energy feedstocks are readily available, and we continue to learn from natural variants that deliver higher sugar saccharification efficiency, which will lead to the generation of improved feedstocks through genetic engineering. (b) Feedstocks go through pretreatment and separation, polysaccharides were hydrolysed with enzymes to release fermentable sugars, which is turned into fuels (bioethanol, biodiesel, and biobutanol) by microbes. Lignin is obtained before or after polysaccharide extraction, depolymerised into aromatic monomers and further converted into value‐added by‐products such as biomaterials and biochemicals.
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References

Alvira P, Tomás‐Pejó E, Ballesteros M and Negro MJ (2010) Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review. Bioresource Technology 101 (13): 4851–4861.

Bhagia S, Muchero W, Kumar R, Tuskan GA and Wyman CE (2016) Natural genetic variability reduces recalcitrance in poplar. Biotechnology for Biofuels 9 (May): 106.

Biswal AK, Hao Z, Pattathil S, et al. (2015) Downregulation of GAUT12 in Populus deltoides by RNA silencing results in reduced recalcitrance, increased growth and reduced xylan and pectin in a woody biofuel feedstock. Biotechnology for Biofuels 8 (March): 41.

Bonawitz ND, Kim JI, Tobimatsu Y, et al. (2014) Disruption of mediator rescues the stunted growth of a lignin‐deficient Arabidopsis mutant. Nature 509 (7500): 376–380.

Brown DM, Goubet F, Wong VW, et al. (2007) Comparison of five xylan synthesis mutants reveals New insight into the mechanisms of xylan synthesis. Plant Journal: For Cell and Molecular Biology 52 (6): 1154–1168.

Cai Y, Zhang K, Kim H, et al. (2016) Enhancing digestibility and ethanol yield of Populus wood via expression of an engineered monolignol 4‐O‐methyltransferase. Nature Communications 7 (June): 11989.

Chen F, Tobimatsu Y, Havkin‐Frenkel D, Dixon RA and Ralph J (2012) A polymer of caffeyl alcohol in plant seeds. Proceedings of the National Academy of Sciences of the United States of America 109 (5): 1772–1777.

Chiniquy D, Sharma V, Schultink A, et al. (2012) XAX1 from glycosyltransferase family 61 mediates xylosyltransfer to rice xylan. Proceedings of the National Academy of Sciences of the United States of America 109 (42): 17117–17122.

Eudes A, George A, Mukerjee P, et al. (2012) Biosynthesis and incorporation of side‐chain‐truncated lignin monomers to reduce lignin polymerization and enhance saccharification. Plant Biotechnology Journal 10 (5): 609–620.

Eudes A, Sathitsuksanoh N, Baidoo EEK, et al. (2015) Expression of a bacterial 3‐dehydroshikimate dehydratase reduces lignin content and improves biomass saccharification efficiency. Plant Biotechnology Journal 13 (9): 1241–1250.

Eudes A, Pereira JH, Yogiswara S, Wang G, et al. (2016) Exploiting the substrate promiscuity of hydroxycinnamoyl‐CoA: shikimate hydroxycinnamoyl transferase to reduce lignin. Plant & Cell Physiology 57 (3): 568–579.

Falter C, Zwikowics C, Eggert D, et al. (2015) Glucanocellulosic ethanol: the undiscovered biofuel potential in energy crops and marine biomass. Scientific Reports 5 (September): 13722.

Foston M, Nunnery GA, Meng X, et al. (2013) NMR a critical tool to study the production of carbon fiber from lignin. Carbon 52 (February): 65–73.

Garvey M, Klose H, Fischer R, Lambertz C and Commandeur U (2013) Cellulases for biomass degradation: comparing recombinant cellulase expression platforms. Trends in Biotechnology 31 (10): 581–593.

Gondolf VM, Stoppel R, Ebert B, et al. (2014) A gene stacking approach leads to engineered plants with highly increased galactan levels in Arabidopsis. BMC Plant Biology 14 (December): 344.

Hallac BB and Ragauskas AJ (2011) Analyzing cellulose degree of polymerization and its relevancy to cellulosic ethanol. Biofuels, Bioproducts & Biorefining 5 (2): 215–225.

Hao Z, Avci U, Tan L, et al. (2014) Loss of Arabidopsis GAUT12/IRX8 causes anther indehiscence and leads to reduced G lignin associated with altered matrix polysaccharide deposition. Frontiers in Plant Science 5 (July): 357.

Hao Z and Mohnen D (2014) A review of xylan and lignin biosynthesis: foundation for studying Arabidopsis irregular xylem mutants with pleiotropic phenotypes. Critical Reviews in Biochemistry and Molecular Biology 49 (3): 212–241.

Higson A and Smith C (2011) Renewable Chemicals Factsheet: Lignin. NNFCC. http://www.Nnfcc.Co.Uk/publications/nnfcc‐Renewable‐Chemicals‐Factsheet‐Lignin

Huang F, Ben H, Pan S, Pu Y and Ragauskas A (2014) The use of combination of zeolites to pursue integrated refined pyrolysis Oil from kraft lignin. Sustainable Chemical Processes 2 (1): 7.

Jia J, Yu B, Wu L, et al. (2014) Biomass enzymatic saccharification is determined by the Non‐KOH‐extractable wall polymer features that predominately affect cellulose crystallinity in corn. PLoS One 9 (9): e108449.

Karlen SD, Zhang C, Peck ML, et al. (2016) Monolignol ferulate conjugates Are naturally incorporated into plant lignins. Science Advances 2 (10): e1600393.

Klinke HB, Thomsen AB and Ahring BK (2004) Inhibition of ethanol‐producing yeast and bacteria by degradation products produced during Pre‐treatment of biomass. Applied Microbiology and Biotechnology 66 (1): 10–26.

Lionetti V, Francocci F, Ferrari S, et al. (2010) Engineering the cell wall by reducing de‐methyl‐esterified homogalacturonan improves saccharification of plant tissues for bioconversion. Proceedings of the National Academy of Sciences of the United States of America 107 (2): 616–621.

Li X, Ximenes E, Kim Y, et al. (2010) Lignin monomer composition affects Arabidopsis cell‐wall degradability after liquid Hot water pretreatment. Biotechnology for Biofuels 3 (December): 27.

Löfstedt J, Dahlstrand C, Orebom A, et al. (2016) Green diesel from kraft lignin in three steps. ChemSusChem 9 (12): 1392–1396.

Mainka H, Täger O, Körner E, et al. (2015) Lignin – an alternative precursor for sustainable and cost‐effective automotive carbon fiber. Journal of Materials Research and Technology 4 (3): 283–296.

Marita JM, Ralph J, Hatfield RD and Chapple C (1999) NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5‐hydroxylase. Proceedings of the National Academy of Sciences of the United States of America 96 (22): 12328–12332.

Marriott PE, Sibout R, Lapierre C, Fangel JU, et al. (2014) Range of cell‐wall alterations enhance saccharification in brachypodium distachyon mutants. Proceedings of the National Academy of Sciences of the United States of America 111 (40): 14601–14606.

Martínez‐Sanz M, Mikkelsen D, Flanagan B, Gidley MJ and Gilbert EP (2016) Multi‐scale model for the hierarchical architecture of native cellulose hydrogels. Carbohydrate Polymers 147 (August): 542–555.

Mortimer JC, Miles GP, Brown DM, et al. (2010) Absence of branches from xylan in Arabidopsis Gux mutants reveals potential for simplification of lignocellulosic biomass. Proceedings of the National Academy of Sciences of the United States of America 107 (40): 17409–17414.

Mubarak M, Shaija A and Suchithra TV (2015) A review on the extraction of lipid from microalgae for biodiesel production. Algal Research 7: 117–123.

Olson DG, McBride JE, Shaw AJ and Lynd LR (2012) Recent progress in consolidated bioprocessing. Current Opinion in Biotechnology 23 (3): 396–405.

Palazzolo MA and Kurina‐Sanz M (2016) Microbial utilization of lignin: available biotechnologies for its degradation and valorization. World Journal of Microbiology and Biotechnology 32 (10): 173.

Parthasarathi R, Sun J, Dutta T, et al. (2016) Activation of lignocellulosic biomass for higher sugar yields using aqueous ionic liquid at Low severity process conditions. Biotechnology for Biofuels 9 (August): 160.

Pawar PM‐A, Koutaniemi S, Tenkanen M and Mellerowicz EJ (2013) Acetylation of woody lignocellulose: significance and regulation. Frontiers in Plant Science 4 (May): 118.

Peña MJ, Zhong R, Zhou G‐K, et al. (2007) Arabidopsis irregular xylem8 and irregular xylem9: implications for the complexity of glucuronoxylan biosynthesis. The Plant Cell 19 (2): 549–563.

Persson Staffan, Kerry Hosmer Caffall, Glen Freshour, et al. (2007) The Arabidopsis Irregular xylem8 Mutant Is Deficient in Glucuronoxylan and Homogalacturonan, Which Are Essential for Secondary Cell Wall Integrity. The Plant Cell 19 (1): 237–255.

Petersen PD, Lau J, Ebert B, et al. (2012) Engineering of plants with improved properties as biofuels feedstocks by vessel‐specific complementation of xylan biosynthesis mutants. Biotechnology for Biofuels 5 (1): 84.

Petti C, Harman‐Ware AE, Tateno M, et al. (2013) Sorghum mutant RGdisplays antithetic leaf shoot lignin accumulation resulting in improved stem saccharification properties. Biotechnology for Biofuels 6 (1): 146.

Rębiś T, Nilsson TY and Inganäs O (2016) Hybrid materials from organic electronic conductors and synthetic‐lignin models for charge storage applications. Journal of Materials Chemistry A: Materials for Energy and Sustainability 4 (5): 1931–1940.

Rubin EM (2008) Genomics of cellulosic biofuels. Nature 454: 841–845.

Salehi Jouzani G and Taherzadeh MJ (2015) Advances in consolidated bioprocessing systems for bioethanol and butanol production from biomass : a comprehensive review. Biofuel Research Journal 2 (1): 152–195.

Serapiglia MJ, Humiston MC, Xu H, et al. (2013) Enzymatic saccharification of shrub willow genotypes with differing biomass composition for biofuel production. Frontiers in Plant Science 4 (March): 57.

Shih PM, Vuu K, Mansoori N, et al. (2016a) A robust gene‐stacking method utilizing yeast assembly for plant synthetic biology. Nature Communications 7 (October): 13215.

Shih PM, Liang Y and Loqué D (2016b) Biotechnology and synthetic biology approaches for metabolic engineering of bioenergy crops. The Plant Journal 87 (1): 103–117.

Shi J, Pattathil S, Parthasarathi R, et al. (2016) Impact of engineered lignin composition on biomass recalcitrance and ionic liquid pretreatment efficiency. Green Chemistry: An International Journal and Green Chemistry Resource: GC 18 (18): 4884–4895.

Smith RA, Schuetz M, Roach M, et al. (2013) Neighboring parenchyma cells contribute to Arabidopsis xylem lignification, while lignification of interfascicular fibers is cell autonomous. The Plant Cell 25 (10): 3988–3999.

Socha AM, Parthasarathi R, Shi J, et al. (2014) Efficient biomass pretreatment using ionic liquids derived from lignin and hemicellulose. Proceedings of the National Academy of Sciences of the United States of America 111 (35): E3587–E3595.

Stewart JJ, Akiyama T, Chapple C, Ralph J and Mansfield SD (2009) The effects on lignin structure of overexpression of ferulate 5‐hydroxylase in hybrid Poplar1. Plant Physiology 150 (2): 621–635.

Studer MH, DeMartini JD, Davis MF, et al. (2011) Lignin content in natural Populus variants affects sugar release. Proceedings of the National Academy of Sciences of the United States of America 108 (15): 6300–6305.

Sumiyoshi M, Nakamura A, Nakamura H, et al. (2013) Increase in cellulose accumulation and improvement of saccharification by overexpression of arabinofuranosidase in rice. PLoS One 8 (11): e78269.

Sun J, Murthy NVS, Shi J, et al. (2016) CO2 enabled process integration for the production of cellulosic ethanol using bionic liquids. Energy & Environmental Science 9 (9): 2822–2834.

Tan L, Eberhard S, Pattathil S, et al. (2013) An Arabidopsis cell wall proteoglycan consists of pectin and arabinoxylan covalently linked to an arabinogalactan protein. The Plant Cell 25 (1): 270–287.

Tobimatsu Y, Chen F, Nakashima J, et al. (2013) Coexistence but independent biosynthesis of catechyl and guaiacyl/syringyl lignin polymers in seed coats. The Plant Cell 25 (7): 2587–2600.

Vargas L, Cesarino I, Vanholme R, Voorend W, et al. (2016) Improving total saccharification yield of Arabidopsis plants by vessel‐specific complementation of caffeoyl shikimate esterase (cse) mutants. Biotechnology for Biofuels 9 (July): 139.

Vega‐Sánchez ME, Loqué D, Lao J, et al. (2015) Engineering temporal accumulation of a Low recalcitrance polysaccharide leads to increased C6 sugar content in plant cell walls. Plant Biotechnology Journal 13 (7): 903–914.

Wang Y‐H, Acharya A, Millie Burrell A, et al. (2013) Mapping and candidate genes associated with saccharification yield in sorghum. Genome/National Research Council Canada = Genome/Conseil National de Recherches Canada 56 (11): 659–665.

Weng J‐K, Mo H and Chapple C (2010) Over‐expression of F5H in COMT‐deficient Arabidopsis leads to enrichment of an unusual lignin and disruption of pollen wall formation. Plant Journal: For Cell and Molecular Biology 64 (6): 898–911.

Wilkerson CG, Mansfield SD, Lu F, et al. (2014) Monolignol ferulate transferase introduces chemically labile linkages into the lignin backbone. Science 344 (6179): 90–93.

Willis JD, Smith JA, Mazarei M, et al. (2016) Downregulation of a UDP‐arabinomutase gene in switchgrass (Panicum virgatum L.) results in increased cell wall lignin while reducing arabinose‐glycans. Frontiers in Plant Science 7: 1580.

Xiong G, Cheng K and Pauly M (2013) Xylan O‐acetylation impacts xylem development and enzymatic recalcitrance as indicated by the Arabidopsis mutant tbl29. Molecular Plant 6 (4): 1373–1375.

Xiong G, Dama M and Pauly M (2015) Glucuronic acid moieties on xylan Are functionally equivalent to O‐acetyl‐substituents. Molecular Plant 8 (7): 1119–1121.

Yang F, Mitra P, Zhang L, et al. (2013) Engineering secondary cell wall deposition in plants. Plant Biotechnology Journal 11 (3): 325–335.

York WS and O'Neill MA (2008) Biochemical control of xylan biosynthesis ‐ which End is Up? Current Opinion in Plant Biology 11 (3): 258–265.

Zhang K, Bhuiya M‐W, Pazo JR, et al. (2012) An engineered monolignol 4‐O‐methyltransferase depresses lignin biosynthesis and confers novel metabolic capability in Arabidopsis. The Plant Cell 24 (7): 3135–3152.

Ziebell A, Gracom K, Katahira R, et al. (2010) Increase in 4‐coumaryl alcohol units during lignification in alfalfa (Medicago sativa) alters the extractability and molecular weight of lignin. The Journal of Biological Chemistry 285 (50): 38961–38968.

Further Reading

Beckham GT, Johnson CW, Karp EM, Salvachúa D and Vardon DR (2016) Opportunities and challenges in biological lignin valorization. Current Opinion in Biotechnology 42 (December): 40–53.

Eudes A, Liang Y, Mitra P and Loqué D (2014) Lignin bioengineering. Current Opinion in Biotechnology 26C: 189–198.

Himmel ME, Ding S‐Y, Johnson DK, et al. (2007) Biomass recalcitrance: engineering plants and enzymes for biofuels production. Science 315 (5813): 804–807.

Jönsson LJ and Martín C (2016) Pretreatment of lignocellulose: formation of inhibitory by‐products and strategies for minimizing their effects. Bioresource Technology 199 (January): 103–112.

Loqué D, Scheller HV and Pauly M (2015) Engineering of plant cell walls for enhanced biofuel production. Current Opinion in Plant Biology 25 (June): 151–161.

Mohr SH, Wang J, Ellem G, Ward J and Giurco D (2015) Projection of world fossil fuels by country. Fuel 141 (February): 120–135.

Mottiar Y, Vanholme R, Boerjan W, Ralph J and Mansfield SD (2016) Designer lignins: harnessing the plasticity of lignification. Current Opinion in Biotechnology 37 (February): 190–200.

Ragauskas AJ, Williams CK, Davison BH, et al. (2006) The path forward for biofuels and biomaterials. Science 311 (5760): 484–489.

Ragauskas AJ, Beckham GT, Biddy MJ, et al. (2014) Lignin valorization: improving lignin processing in the biorefinery. Science 344 (6185): 1246843.

Somerville C, Youngs H, Taylor C, Davis SC and Long SP (2010) Feedstocks for lignocellulosic biofuels. Science 329 (5993): 790–792.

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Hao, Zhangying, and Loqué, Dominique(Jul 2017) Plant Cell Walls: Improved Resources for Biofuels and Value‐Added Products through Genetic Engineering. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001684.pub2]