BIOREFINERY FOR BIOPOLYMERS:NEW TOOLS FOR BIOMATERIALS PRODUCTION, DEGRADATION AND SUSTAINABLE FUNCTIONALIZATION
Biopolymers are attractive “green” alternatives to conventional petroleum-based plastics, however, their sustainable exploitation is hampered by the high production costs. In this PhD thesis, an Escherichia coli recombinant system (LipoA) was constructed to allow production of Polyhydroxyalkanoates...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | Italian English |
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2018
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| Online Access: | http://www.fedoa.unina.it/12278/ http://www.fedoa.unina.it/12278/7/vastano_marco_30_COMPLETA.pdf |
| Summary: | Biopolymers are attractive “green” alternatives to conventional petroleum-based plastics, however, their sustainable exploitation is hampered by the high production costs. In this PhD thesis, an Escherichia coli recombinant system (LipoA) was constructed to allow production of Polyhydroxyalkanoates (PHAs). The system was engineered with a newly isolated PHAs biosynthetic operon from Bacillus cereus 6E/2 and tested for PHAs production on different carbon sources. Results highlighted the LipoA peculiar specificity to drive the incorporation of 3-hydroxyhexanoate monomers (>40%), whatever was the supplied fatty acid. To increase polymer production, media optimization and system engineering were applied. In this frame, two new PHA producing systems were developed considering i) the expression levels of the recombinant PHA bio-synthetic proteins (LipoB) and ii) the "host metabolic background" (LipoC) yielding to a 6-fold increment of mcl-PHA yields. Polymers were characterized revealing a low grade of crystallinity and hydrophobic features. To enhance biopolymer properties and expand fields of applicability, PHAs were enzymatically functionalized. Commercial lipase B from Candida antarctica (CaLB) was able to catalyse coupling of PHA with dimethyl itaconate (DMI) as well as with polyethylene glycol (PEG). The obtained functional hydrophilic biopolymers open new perspectives for application of PHAs in the biomedical field thanks to the possibility of easy coupling of bioactive compounds on the lateral C=C of DMI and to the enhanced hydrophilicity conferred by the PEG moieties. The enzymatic strategy was also applied for sustainable synthesis of oligoesters. Catalytic potential of immobilized Thermobifida cellulosilytica cutinase 1 (Thc_Cut1) was investigated. Three different carriers, linked to the enzyme using a novel nontoxic His-tag method based on chelated Fe(III) ions, were tested. Selectivity chain (diols-diesters) and recyclability studies in solvent-free environment were conducted. Results not only revealed ... |
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