Post on 01-May-2015
Biotecnologie ambientali
Plastiche biodegradabili e altri polimeri da piante
Le piante coltivate e la sindrome da domesticazione: shattering e dormienza
Rischi e benefici ambientali delle piante transgeniche in paragone a quelle convenzionali.
Convenzione di Rio, Protocollo di Cartagena e normativa sulle piante create con tramite ingegneria genetica
Piante per una maggiore sostenibilità ambientale (es. plastiche biodegradabili), per il risanamento (fitodepurazione) e come biosensori di contaminazione.
Interazione pianta-microrganismo: le risposte di difesa delle piante e generazione di specie resistenti. Tumori vegetali e trasgenesi naturale.
Interazione simbiotiche pianta-microrganismo: fissazione dell’azoto (batteri azoto fissatori) ed efficienza nella nutrizione minerale (funghi vescicolo arbuscolari)
PROGRAMMA
Sono richiesti > 50 anni per la degradazione La maggior parte finisce in discarica o agli inceneritori La dispersione impropria (accidentale o volontaria) comporta inquinamento ambientale e danni a diversi organismi*.
* http://www.dailymail.co.uk/news/article-519770/Banish-The-Bags-The-Mail-launches-campaign-clean-country---planet.html
Plastiche
With a production of 265 million tonnes p.a. (2009), plastics are a necessity in today’s economy. In one year, roughly 80 million metric tons of polyethylene will be manufactured. The average cost of polyethylene is ≈1 €/kg.
http://en.european-bioplastics.org/technologymaterials/materials/
http://www.acquistiverdi.it/sites/default/files/imagecache/Original_confirma/images/prodotti/shopper_in_mater_bi_novamont.jpg
Mater-bi Novamont
Bioplastiche non equivale a biodegradabili; nell’accezione comune significa: prodotte a partire da organismi e non da petrolio.Conviene distinguere Biobased e Biodegradable
Qualche numero sulle plastiche
~50 Mt produzione annuale europea
di cui solo 0.7 Mt sono Bioplastiche
Target realistico: rimpiazzare il 20% della plastica attualmente prodotta con plastica biodegradabile:
Quelle biodegradabili sono essenzialmente:
PLA (Poly Lactic Acid) 150,000 t / y
PHA (Poly Hydroxy Alkanoates) 50,000 t / y
Starch-based biopolymer 120,000 t / y
Con una resa (realistica) di 2 t/ha di prodotto finale diventa un target fattibile
Produzione globale di amido 70 Mt (2010) prezzo 0.50 - 1.30 € / kg
(it excludes starchy plants consumed directly) (in funzione di origine, purezza…)
In Europe, the current price for starch plastics ranges from €2.00 to €5.00 per kg depending on the grade.
http://www.packaging-int.com/upload/image_files/suppliers/images/companies/2606/b-cups-l.jpg
StarchProteinOilsCelluloseRubberLigninCyanophycin… PHBPLA
van Beilen & Poirier (2012) Plants as factories for bioplastics and other novel biomaterials
Polyhydroxyalkanoates (PHAs)
• Polyesters accumulated inside microbial cells as carbon & energy source storage
Ojumu et al., 2004
http://www.unil.ch/webdav/site/dbmv/shared/Poiriers/Fig1.jpg
~250 different bacteria have been found to produce some form of PHAs
PHB/PHA sono biodegradabili, ma hanno un costo non (ancora) competitivo con la plastica prodotta da petrolio
http://www.unil.ch/webdav/site/dbmv/shared/Poiriers/Fig2.jpg
La via biosintetica del PHB parte dal Acetil-CoA ed è composta da 3 enzimi
PHA synthasePHA synthaseββ-ketothiolase-ketothiolaseNADPH-dependent acetoacetyl-CoA reductaseNADPH-dependent acetoacetyl-CoA reductase
http://www.unil.ch/webdav/site/dbmv/shared/Poiriers/peroxisomal_PHB_and_citrate_synthase.jpeg
Metabolic pathways leading to the production of PHB, P(HB-co-HV) and mclPHA in plants
Transgenic plant producing the biodegradable plastic polyhydroxybutyrate (PHB). PHB is seen by electron microscopy as white granules inside the nucleus of a leaf mesophyll cell of Arabidopsis thaliana.
Science 256:520-523 (1992)
La sintesi di PHB in pianta è stata dimostrata 20 anni fa
Transgenic plant producing the biodegradable plastic polyhydroxybutyrate (PHB). The PHB granules are visualised by epifluorescence microscopy as foci of red fluorescence.
http://www.unil.ch/dbmv/page13444_en.html
Numerosi ostacoli che imponevano basse rese sono stati superati
(es. localizzazione nel plastidio/perossisoma invece che nel citosol)
http://www.unil.ch/webdav/site/dbmv/shared/Poiriers/Fig5.jpg
Molti tentativi. In genere le rese sono basse. Più alta è la resa, maggiori sono gli effetti sulla crescita
Bohmert-Tatarev et al., (2011) Plant Physiology 155:1690–1708.
T0 plants that were capable of producing up to 18.8% dry weight PHB in samples of leaf tissue. These plants were fertile and produced viable seed. T1 plants producing up to 17.3% dry weight PHB in samples of leaf tissue and 8.8% dry weight PHB in the total biomass of the plant were also isolated.
To be commercially viable PHA must be > 15% dry weight
Acinetobacter sp. Thiolase (phaA) and synthase (phaC; Schembri et al., 1995) and the Bacillus megaterium reductase (phaB; McCool and Cannon, 1999) and aadA gene conferring resistance to spectinomycin
A=tiolasiC=sintasi B=reduttasi
spectinomycinR
Expected genetic arrangement of transformants (pCAB)
genetic arrangement of the wild-type psbA locus
Southern blot of PstI-digested genomic DNA from transplastomic and wild-type lines
3.04 kb band
PCR primers
Le piante hanno integrato nel DNA plastidiale il costrutto
6 weeks 10 weeks
Plants from pCAB transformations were found to possess a slightly paler green phenotype and grew slower than wild-type plants
T0 plants that were capable of producing up to 18.8% dry weight PHB in samples of leaf tissue. These plants were fertile and produced viable seed.
G, PHB granules;
P, plastoglobuli;
S, starch granules.
Bars = 1 μm.
PHB accumulation in tobacco leaves
PHB granules;
Transmission electron micrographs from samples of leaf 17 (where leaf 1 is defined as the oldest leaf of a plant)
PHB production in T1 progeny of CAB lines 2 and 6.
T1 Lines have delayed flowering but are fertile
Il carattere è trasmissibile e sembra stabile
La crescita è rallentata (ci mettono più tempo a fiorire) e raggiungono una minore altezza
Screening T1 seeds obtained from self-pollination on medium containing spectinomycin. This procedure allows the detection of residual wild-type copies of the plastome in the parent plant, since these copies should be maternally inherited, producing seeds with spectinomycin-sensitive seedlings. Range: 0.6% to 11.6% depending on the line analyzed
La ridotta velocità di crescita alla fine comporta una biomassa minore
Synthesis of a biopolymer at a level of 10% dry weight in leaves of sugar beet would yield 0.5 tonnes of biopolymer /ha. With 2 Mha of sugar beet currently grown in the EU, this single crop could yield 1 Mt of biopolymers/ year in addition to 24 Mt of sugar/ year.
Yields of tobacco leaf biomass can be increased by using different agronomic practices compared to growing tobacco for smoking, and yields of up to 14 tonnes/ ha have been reported, which compares reasonably well with sugar beet at 18 tonnes/ ha
In sintesi: le bioplastiche biodegradabili da piante sono a portata di mano, ma solo se il presente clima ostile cambia...
GommaMercato mondiale della gomma:
Naturale 9 Mt/y 1.80 €/kgSintetica 3 Mt/y 1.30 €/kg
Perché la produzione minore se il prezzo è inferiore?
La qualità della gomma sintetica è inferiore, specialmente per applicazioni dove sono richieste alte prestazioni.
The polymer chain has two trans- and multiple cis-bonds
Schematic pathway for rubber biosynthesis from isopentenyl diphosphate (IPP).
La gomma naturale è ancora prodotta come ai primi del 1900Circa il 90% deriva dalle piantagioni del Sud-Est asiatico
Altre piante producono lattice che contiene gomma
Sources of natural rubber. (a) Tapping of the Para rubber tree (H. brasiliensis); (b) a field of Guayule (P. argentatum) at Ehrenberg, Arizona (kindly provided by Yulex Corporation; http://www.yulex.com/); (c) Russian dandelion (T. koksaghyz) (kindly provided by Dirk Prüfer); (d) Canadian goldenrod (S. canadensis).
Non è solo la sintesi del polimero che deve essere aumentata, ma anche quella del lattice e delle strutture che lo contengono
Biosintesi della gomma a partire dall’isopentenil pirofosfato (IPP)
Meccanismo proposto di polimerizzazione tramite carbocatione
Altri materiali interessanti
McQualter, R.B., Chong, B.F., Meyer, K., Van Dyk, D.E., O'Shea, M.G., Walton, N.J., Viitanen, P.V. and Brumbley, SM. (2005) Initial evaluation of sugarcane as a production platform for p-hydroxybenzoic acid. Plant Biotechnol. J. 3, 29-41.
p-hydroxybenzoic acid (pHBA)
The global market for Liquid Crystal Polymers is approximately 10,000 metric tons per year, with applications in electrical and optical connectors, integrated circuit boards, vehicle ignition components, and mobile phone components. LCPs are thermotropic polyesters and the major monomer used in the manufacture of these copolymers is pHBA
Cyanophycin, or multi-L-arginyl-poly (L-aspartic acid), is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups (http://en.wikipedia.org/wiki/Cyanophycin )
BibliografiaBohmert-Tatarev et al., (2011) High Levels of Bioplastic Are Produced in Fertile Transplastomic Tobacco Plants Engineered with a Synthetic Operon for the Production of Polyhydroxybutyrate Plant Physiology 155:1690–1708.
Tilbrook K, Gebbie L, Schenk PM, Poirier Y, Brumbley SM (2011) Peroxisomal polyhydroxyalkanoate biosynthesis is a promising strategy for bioplastic production in high biomass crops. Plant Biotechnol J.
van Beilen and Poirier (2008) Production of renewable polymers from crop plants. Plant J. 54:684–701.
Poirier, Y., Dennis, D.E., Klomparens, K. and Somerville, C. (1992) Polyhydroxybutyrate, a biodegradable thermoplastic, produced in transgenic plants. Science, 256, 520–523.
Shen, Haufe, Patel (2009) Product overview and market projection of emerging bio-based plastics. http://www.epnoe.eu/content/download/7670/109501/file/PROBIP2009%20Final%20June%202009.pdf
van Beilen and Poirier (2007) Establishment of new crops for the production of natural rubber. Trends Biotechnol. 25:522-9 in Plants as factories for industrial products, pharmaceuticals, biomaterials, and bioenergy).
Mooney (2010) The second green revolution? Production of plant-based biodegradable plastics. Biochem. J. 418:219–232.