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


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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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. [doi: 10.1002/9780470015902.a0001684.pub2]