Plant biotechnology for lignocellulosic biofuel production

Abstract

SummaryLignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin-carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall-degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat-stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.

Engineering of plant cell walls for enhanced biofuel production

“…Lignin is mainly composed of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units derived from the random polymerization of p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol, respectively. Significant progress on the modification of lignin structure, content or distribution has been achieved within the last years to reduce overall biomass recalcitrance and improve saccharification yield without compromising biomass yield (see recent reviews: [9][10][11]). The lignin-engineering field is rapidly evolving and multiple approaches are currently developed to reduce its recalcitrance, minimize lignin waste stream, and/or valorize it [7,[12][13][14].…”

The Translation Initiation Factor 1A (TheIF1A) from Tamarix hispida Is Regulated by a Dof Transcription Factor and Increased Abiotic Stress Tolerance

“…To better analyze the salt and mannitol response of TheIF1A , 295-bp of the TheIF1A sequence was cloned into a reconstructive ProKII vector to construct the RNAi-suppression vector RNAi::TheIF1A (Supplementary Figure S5) (Zhang et al, 2012; Li et al, 2014). The forward and reverse primers are presented in Supplementary Table S2.…”

Plant Molecular Farming: Much More than Medicines

“…The complete hydrolysis of cellulose to glucose requires three enzymes (an exo-1,4-β-glucanase, an endo-1,4-β-glucanase, and a β-D-glucosidase), and a second stream of fermentable pentoses can be derived from xylan using the enzymes endo-1,4-β-D-xylanase, β-xylosidase, and α-glucuronidase; most of these enzymes have already been successfully expressed in plants (92). Maize lines individually expressing endo-β-1,4-glucanase and endo-β-1,4-xylanase …”