Influence of pH on the Molecular Weight of Poly-3-hydroxybutyric Acid (P3HB) Produced by Recombinant Escherichia coli

Abstract

The production of ultrahigh molecular weight poly-3-hydroxybutyric acid (P3HB) from carbohydrates by recombinant Escherichia coli harboring genes from Ralstonia eutropha was evaluated. In shaken-flask experiments, E. coli XL1 Blue harboring plasmid pSK::phaCAB produced P3HB corresponding to 40 and 27% of cell dry weight from glucose and xylose, respectively. Cultures in bioreactor using glucose as the sole carbon source at variable pH values (6.0, 6.5, or 7.0) allowed the production of P3HB with molecular weight varying between 2.0 and 2.5 MDa. These figures are significantly higher than the values often obtained by natural bacterial strains (0.5-1.0 MDa). Contrary to reports of other authors, no influence of pH was observed on the molecular weight of the polymer produced. Using xylose, P3HB with high molecular weight was also produced, indicating the possibility to produce these polymers from lignocellulosic materials.

Biotechnological strategies to improve production of microbial poly‐(3‐hydroxybutyrate): a review of recent research work

“…The pH of the broth culture is a critical parameter for the optimal production of P(3HB). Reports have been published about the influence of this parameter on the concentration and molecular weight of this polymer (Kusaka et al ., ; Myshkina et al ., ; Bocanegra et al ., ).…”

“…More recently, Bocanegra and colleagues () evaluated P(3HB) production by recombinant E. coli XL‐1 Blue harbouring plasmid pSK:: phbCAB at three different pHs (6.0, 6.5 and 7.0). Cultures in bioreactor using glucose as the sole carbon source at variable pH values (6.0, 6.5, or 7.0) allowed the production of P(3HB) with MMW varying between 2.0 and 2.5 × 10 3 kDa.…”

Seleção de genes codificadores de PHA sintases para a construção de recombinantes em Burkholderia sacchari e Pseudomonas sp e avaliação da produção de polihidroxialcanoatos com diferentes composições monoméricas.

“…A expressão de genes codificadores de PHA sintase em hospedeiros heterólogos tem levado à produção de PHA com novas propriedades (BOCANEGRA et al, 2013;SCHONEBAUM;STEINBUCHEL, 1996;VALENTIN et al, 1994 GILLESPIE et al, 2002;LEFEVRE et al, 2008). Além disso, também é possível buscar organismos produtores de PHA como fonte de genes para expressão heteróloga.…”