Engineering the diversity of polyesters

Biocompounds from Haloarchaea and Their Uses in Biotechnology

“…To date, over 150 structural variations have been reported [78,79]. There are different ways to classify these biopolymers: on the one hand, depending upon the number of carbon atoms in the monomers, PHAs are classified into two distinct groups [77,79]: scl-PHAs (short-chain length PHAs), whose monomers consist of 3-5 carbon atoms, and mcl-PHAs (medium chain length PHAs), composed of monomers having 6-14 carbon atoms; on the other hand, PHAs can be classified depending on the type of monomers that form them [78,79]: the homopolymers, made of identical monomers, include PHB (poly-3-hydroxybutyrate), P3HP (poly-3-hydroxypropionate), P4HB (poly-4-hydroxybutyrate), PTE (polythioester), PLA (polylactic acid), and PHV(polyhydroxyvalerate), among others; copolymers (also called heteropolymers), derived from more than one species of monomer like PHBV (polyhydroxybutyrate-valerate). In addition, the variety of PHAs is higher considering more aspects, such as the structure of their side chains (saturated or not) and the presence of aromatic or halogenated groups in their monomers [77].…”

“…PHAs are synthesized by four natural pathways [78]: pathway I, that converts sugar to acetylCoA, acetoacetyl-CoA to 3-hydroxybutyryl-CoA which is polymerized to PHB; pathway II, that begins from fatty acids to produce R-3-hydroxyacyl-CoA monomers for PHA synthesis via β-oxidation cycle; pathway III, that converts acetyl-CoA, malonyl-CoA to 3-ketoacyl-ACP into R-3-hydroxyacyl-CoA monomers; pathway IV converts butyric acid to S-3-hydroxybutyryl-CoA, then to acetyl-CoA to form PHA monomers.…”

“…The enzymes responsible for this reaction are PHA synthases. Therefore, it is considered that the key enzymes for PHA production are the polyester synthases [76,78,80]. In the Bacteria domain, where these kind of proteins have been studied extensively, they are divided into four classes depending on the subunit composition and their substrate [76,77,80].…”

Aproveitamento de torta do tabaco gerado na produção de biodiesel para a obtenção de bioplástico

“…Já foram encontrados pelo menos 150 tipos de unidades monoméricas dos PHA's -ácidos hidroxialcanóicos (HAs) -sendo os mais comuns o hidroxibutirato (HB), hidroxivalerato (HV), hidroxipropionato (HP) e o hidroxihexanoato (HHx) (MENG et al, 2014;STEINBÜCHEL e VALENTIN, 1995).…”

“…Nas bactérias, a síntese de PHAs pode envolver muitas enzimas, dependendo da via metabólica que será ativada e dos monômeros que serão polimerizados; já são conhecidas 45 enzimas e 12 rotas (MENG et al, 2014). A principal via de formação de PHAs envolve pelo menos três enzimas: PhaA (β-cetoacil-CoA tiolase), PhaB (acetoacetil-CoA redutase/desidrogenase, dependente de NADPH) e PhaC (PHAsintase) (JENDROSSEK e PFEIFFER, 2014).…”