Recombinant hyperthermophilic enzyme expression in plants: a novel approach for lignocellulose digestion

Mir, Bilal Ahmad; Mewalal, Ritesh; Mizrachi, Eshchar; Myburg, Alexander Andrew; Cowan, Don A.

doi:10.1016/j.tibtech.2014.03.003

Cited by 20 publications

(27 citation statements)

References 79 publications

(148 reference statements)

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“…Plant expression of CWLEs with inducible activity (i.e., optimal activity at pH and temperature values extremely different from those of the plant) can be used to further reduce (dangerous) residual activities in vivo, thus preserving plant health and productivity. Notably, accumulation of HCWLEs was achieved in the apoplast of transgenic Arabidopsis thaliana plants without adverse effects on plant growth [120,121]. When compared to their mesophilic enzymatic counterparts, HCWLEs have several advantages, which are mainly dependent on the temperature at which HCWLEs are active [122].…”

Section: Heterologous Expression Of Cwles In Plantsmentioning

confidence: 99%

Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes

et al. 2019

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Energy demand is constantly growing, and, nowadays, fossil fuels still play a dominant role in global energy production, despite their negative effects on air pollution and the emission of greenhouse gases, which are the main contributors to global warming. An alternative clean source of energy is represented by the lignocellulose fraction of plant cell walls, the most abundant carbon source on Earth. To obtain biofuels, lignocellulose must be efficiently converted into fermentable sugars. In this regard, the exploitation of cell wall lytic enzymes (CWLEs) produced by lignocellulolytic fungi and bacteria may be considered as an eco-friendly alternative. These organisms evolved to produce a variety of highly specific CWLEs, even if in low amounts. For an industrial use, both the identification of novel CWLEs and the optimization of sustainable CWLE-expressing biofactories are crucial. In this review, we focus on recently reported advances in the heterologous expression of CWLEs from microbial and plant expression systems as well as some of their industrial applications, including the production of biofuels from agricultural feedstock and of value-added compounds from waste materials. Moreover, since heterologous expression of CWLEs may be toxic to plant hosts, genetic strategies aimed in converting such a deleterious effect into a beneficial trait are discussed.

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Section: Heterologous Expression Of Cwles In Plantsmentioning

confidence: 99%

Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes

et al. 2019

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“…Hydrolases from thermophilic microorganisms such as Acidothermus cellulolyticus and Thermomonospora fusca, which are able to hydrolyze cellulose at high temperatures (81 and 75°C respectively), have been expressed in various plant species with no harmful effects [37,56,[77][78][79], while still having the desired effect of improving the ease of breakdown of plant material after harvest. Moreover, thermophilic enzymes are activated during post-harvest processing providing more advantages and applications in cellulosic ethanol production including simplifying processing and reducing exogenous enzyme loading [38].…”

Section: Strategies To Prevent Harmful Effects Of Glycosyl Hydrolase mentioning

confidence: 99%

“…These include studies showing expression levels up to 26 % total soluble protein (TSP) in Arabidopsis and 50 % TSP in tobacco leaves [29][30][31][32][33][34][35][36][37]. Although there is potential for high-level enzyme production in these plant systems, the expression of cell wall-degrading enzymes in the biomass of the lignocellulosic feedstocks themselves has added advantages [38]. Production of enzymes in the biomass feedstock would allow one crop to serve as both an enzyme provider and a biomass substrate for enzymatic saccharification.…”

Section: Introductionmentioning

confidence: 99%

“…Hyperthermophilic enzymes will be activated at high temperature, during pretreatment, allowing enzymatic saccharification and pretreatment to be conducted in the same reactor [38]. In both scenarios (basic and advanced), reduced amounts of microbe produced exogenous cellulases and hemicellulases will be required to release equivalent amounts of fermentable sugars.…”

Section: Introductionmentioning

confidence: 99%

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Expression of Glycosyl Hydrolases in Lignocellulosic Feedstock: An Alternative for Affordable Cellulosic Ethanol Production

2016

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Ethanol produced from lignocellulosic feedstock is a promising alternative to fossil fuels and corn-sourced ethanol. However, it creates unique challenges in terms of requirements for breakdown to fermentable sugars, including the need for pretreatment and enzymatic hydrolysis of structural carbohydrates. Hydrolases from microorganisms are currently utilized for biomass hydrolysis in the production of lignocellulosic ethanol; however, expressing these hydrolases in lignocellulosic feedstock is a favorable alternative, due to the large availability of biomass and the potential for the feedstock to play a dual role as both biomass substrate and enzyme provider. This review summarizes recent achievements in hydrolytic enzyme expression in a variety of model plants and potential feedstocks, including strategies to improve enzyme yield and to prevent deleterious effects on plants hosts. We propose possible scenarios for utilizing enzyme-expressing transgenic feedstock and illustrate the potential benefits of using these crops for ethanol production. Furthermore, challenges are highlighted and potential solutions proposed to move the field forward to cost-comparable lignocellulosic ethanol.

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“…Importantly, we include only enzymes that are active in planta concurrent with cell wall development. The engineering of plants to accumulate hyperthermophilic or inactive cell wall-degrading enzymes has been well reviewed in other works (Mir et al, 2014;Damm et al, 2016;Park et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Engineering of Bioenergy Crops: Dominant Genetic Approaches to Improve Polysaccharide Properties and Composition in Biomass

Brandon

Scheller

2020

Front. Plant Sci.

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Large-scale, sustainable production of lignocellulosic bioenergy from biomass will depend on a variety of dedicated bioenergy crops. Despite their great genetic diversity, prospective bioenergy crops share many similarities in the polysaccharide composition of their cell walls, and the changes needed to optimize them for conversion are largely universal. Therefore, biomass modification strategies that do not depend on genetic background or require mutant varieties are extremely valuable. Due to their preferential fermentation and conversion by microorganisms downstream, the ideal bioenergy crop should contain a high proportion of C6-sugars in polysaccharides like cellulose, callose, galactan, and mixed-linkage glucans. In addition, the biomass should be reduced in inhibitors of fermentation like pentoses and acetate. Finally, the overall complexity of the plant cell wall should be modified to reduce its recalcitrance to enzymatic deconstruction in ways that do no compromise plant health or come at a yield penalty. This review will focus on progress in the use of a variety of genetically dominant strategies to reach these ideals. Due to the breadth and volume of research in the field of lignin bioengineering, this review will instead focus on approaches to improve polysaccharide component plant biomass. Carbohydrate content can be dramatically increased by transgenic overexpression of enzymes involved in cell wall polysaccharide biosynthesis. Additionally, the recalcitrance of the cell wall can be reduced via the overexpression of native or non-native carbohydrate active enzymes like glycosyl hydrolases or carbohydrate esterases. Some research in this area has focused on engineering plants that accumulate cell wall-degrading enzymes that are sequestered to organelles or only active at very high temperatures. The rationale being that, in order to avoid potential negative effects of cell wall modification during plant growth, the enzymes could be activated post-harvest, and post-maturation of the cell wall. A potentially significant limitation of this approach is that at harvest, the cell wall is heavily lignified, making the substrates for these enzymes inaccessible and their activity ineffective. Therefore, this review will only include research employing enzymes that are at least partially active under the ambient conditions of plant growth and cell wall development.

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Recombinant hyperthermophilic enzyme expression in plants: a novel approach for lignocellulose digestion

Cited by 20 publications

References 79 publications

Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes

Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes

Expression of Glycosyl Hydrolases in Lignocellulosic Feedstock: An Alternative for Affordable Cellulosic Ethanol Production

Engineering of Bioenergy Crops: Dominant Genetic Approaches to Improve Polysaccharide Properties and Composition in Biomass

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