Modification of acetoacetyl-CoA reduction step in Ralstonia eutropha for biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from structurally unrelated compounds.
Microb Cell Fact
; 18(1): 147, 2019 Aug 29.
Article
em En
| MEDLINE
| ID: mdl-31466527
ABSTRACT
BACKGROUND:
Poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) [P(3HB-co-3HHx)] is a bacterial polyester with high biodegradability, even in marine environments. Ralstonia eutropha has been engineered for the biosynthesis of P(3HB-co-3HHx) from vegetable oils, but its production from structurally unrelated carbon sources remains unsatisfactory.RESULTS:
Ralstonia eutropha strains capable of synthesizing P(3HB-co-3HHx) from not only fructose but also glucose and glycerol were constructed by integrating previously established engineering strategies. Further modifications were made at the acetoacetyl-CoA reduction step determining flux distribution responsible for the copolymer composition. When the major acetoacetyl-CoA reductase (PhaB1) was replaced by a low-activity paralog (PhaB2) or enzymes for reverse ß-oxidation, copolyesters with high 3HHx composition were efficiently synthesized from glucose, possibly due to enhanced formation of butyryl-CoA from acetoacetyl-CoA via (S)-3HB-CoA. P(3HB-co-3HHx) composed of 7.0 mol% and 12.1 mol% 3HHx fractions, adequate for practical applications, were produced at cellular contents of 71.4 wt% and 75.3 wt%, respectively. The replacement by low-affinity mutants of PhaB1 had little impact on the PHA biosynthesis on glucose, but slightly affected those on fructose, suggesting altered metabolic regulation depending on the sugar-transport machinery. PhaB1 mostly acted in the conversion of acetoacetyl-CoA when the cells were grown on glycerol, as copolyester biosynthesis was severely impaired by the lack of phaB1.CONCLUSIONS:
The present results indicate the importance of flux distribution at the acetoacetyl-CoA node in R. eutropha for the biosynthesis of the PHA copolyesters with regulated composition from structurally unrelated compounds.
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Base de dados:
MEDLINE
Assunto principal:
Acil Coenzima A
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Cupriavidus necator
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Ácido 3-Hidroxibutírico
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Plásticos Biodegradáveis
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article