title: Production by Tobacco Transplastomic Plants of Recombinant Fungal and Bacterial Cell-Wall Degrading Enzymes to Be Used for Cellulosic Biomass Saccharification.
abstract: Biofuels from renewable plant biomass are gaining momentum due to climate change related to atmospheric CO2 increase. However, the production cost of enzymes required for cellulosic biomass saccharification is a major limiting step in this process. Low-cost production of large amounts of recombinant enzymes by transgenic plants was proposed as an alternative to the conventional microbial based fermentation. A number of studies have shown that chloroplast-based gene expression offers several advantages over nuclear transformation due to efficient transcription and translation systems and high copy number of the transgene. In this study, we expressed in tobacco chloroplasts microbial genes encoding five cellulases and a polygalacturonase. Leaf extracts containing the recombinant enzymes showed the ability to degrade various cell-wall components under different conditions, singly and in combinations. In addition, our group also tested a previously described thermostable xylanase in combination with a cellulase and a polygalacturonase to study the cumulative effect on the depolymerization of a complex plant substrate. Our results demonstrate the feasibility of using transplastomic tobacco leaf extracts to convert cell-wall polysaccharides into reducing sugars, fulfilling a major prerequisite of large scale availability of a variety of cell-wall degrading enzymes for biofuel industry.
authors.affiliation: Dipartimento di Biologia e Biotecnologie, Università di Pavia, Via Ferrata 9, 27100 Pavia, Italy ; Dipartimento de Biologie Végétale, Université de Geneva, 30 Quai Ernest Ansermet, Sciences III, 1211 Genève, Switzerland.
authors.forename: Paolo
authors.identifier: 0000-0003-0587-7621
authors.initials: P
authors.lastname: Longoni
authors.affiliation: Plant Transformation Group, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Sadhu
authors.initials: S
authors.lastname: Leelavathi
authors.affiliation: Dipartimento di Biologia e Biotecnologie, Università di Pavia, Via Ferrata 9, 27100 Pavia, Italy ; Centre of Sustainable Livelihood (CSL), Vaal University of Technology, Vanderbijlpark 1900, South Africa.
authors.forename: Enrico
authors.initials: E
authors.lastname: Doria
authors.affiliation: Plant Transformation Group, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Vanga Siva
authors.initials: VS
authors.lastname: Reddy
authors.affiliation: Dipartimento di Biologia e Biotecnologie, Università di Pavia, Via Ferrata 9, 27100 Pavia, Italy.
authors.forename: Rino
authors.initials: R
authors.lastname: Cella
mesh_terms: D056804:Biofuels; D018533:Biomass; D002473:Cell Wall / Q000737:chemistry / Q000201:enzymology; D044602:Cellulases / Q000737:chemistry / Q000235:genetics*; D002736:Chloroplasts / Q000201:enzymology; D004798:Enzymes / Q000737:chemistry / Q000235:genetics*; D005285:Fermentation; D008031:Lignin / Q000737:chemistry; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics*; D011134:Polysaccharides / Q000737:chemistry; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics*
chemical_list: D056804:Biofuels; D004798:Enzymes; D011134:Polysaccharides; D008031:Lignin; D044602:Cellulases