β-Ketothiolases catalyze the first step of poly(3-hydroxybutyrate) [poly(3HB)] biosynthesis in bacteria by condensation of two acetyl coenzyme A (acetyl-CoA) molecules to acetoacetyl-CoA and also take part in the degradation of fatty acids. During growth on propionate or valerate, Ralstonia eutropha H16 produces the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)]. In R...

BACKGROUND Although the production of poly-beta-hydroxybutyrate (PHB) has many biological, energetic and environmental advantages over chemically synthesized polymers, synthetic polymers continue to be produced industrially since the productivities of fermentation processes fr PHB are not yet economically competitive. Improvement of a PHB fermentation requires good understanding and optimizatio...

Molar growth yields were determined from chemostat cultures of Hydrogenomonas eutropha on succinate and on fumarate. The yields from culture on succinate were about 12 g higher than on fumarate. Assuming this difference to be equivalent to 1 molecule of adenosine triphosphate, it is concluded that the oxidation by oxygen of the Hydrogenomonas cytochrome b yields 1 molecule of adenosine triphosp...

The substrate specificity of polyhydroxyalkanoate (PHA) synthase 1 (PhaC1(Pp), class II) from Pseudomonas putida GPo1 (formerly known as Pseudomonas oleovorans GPo1) was successfully altered by localized semirandom mutagenesis. The enzyme evolution system introduces multiple point mutations, designed on the basis of the conserved regions of the PHA synthase family, by using PCR-based gene fragm...

mathematical modeling and simulation of microbial polyhydroxybutyrate (phb) production process is beneficial for optimization, design, and control purposes. in this study a batch model developed by mulchandani et al., [1] was used to simulate the process in matlab environment. it was revealed that the kinetic model parameters were estimated off the optimal or at a local optimal point. therefore...

In contrast to its parent strain, transposon Tn5-Mob insertion mutant HB6 of the facultative chemoautotroph Ralstonia eutropha was unable to grow organoautotrophically on formate and exhibited no activity of Mo-dependent, membrane-bound formate dehydrogenase (M-FDH) when cultivated mixotrophically on fructose plus formate. The activity of another molybdoenzyme, the soluble, NAD+-linked formate ...

The polyhydroxyalkanoate (PHA) copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB-co-HHx)] has been shown to have potential to serve as a commercial bioplastic. Synthesis of P(HB-co-HHx) from plant oil has been demonstrated with recombinant Ralstonia eutropha strains expressing heterologous PHA synthases capable of incorporating HB and HHx into the polymer. With these strains, howeve...

Relatively little has been published on the capacity of Hydrogenomonas to utilize amino acids under conditions supporting either autotrophic or heterotrophic growth. DeCicco and Umbreit (4) found that wild-type H. facilis utilizes either phenylalanine or tyrosine for growth with glucose as the main carbon and energy source. Atkinson (2) noted that H. facilis growing autotrophically in the prese...

The undefined poly(3-hydroxybutyrate)- (PHB-) negative mutant R. eutropha PHB-4 was generated in 1970 by 1-nitroso-3-nitro-1-methylguanidine (NMG) treatment. Although being scientific relevant, its genotype remained unknown since its isolation except a recent first investigation. In this study, the mutation causing the PHA-negative phenotype of R. eutropha PHB-4 was confirmed independently: seq...

Polyhydroxyalkanoates (PHAs) are polyoxoesters that are produced by many bacteria and that accumulate as intracellular granules. Phasins (PhaP) are proteins that accumulate during PHA synthesis, bind PHA granules, and promote further PHA synthesis. Interestingly, PhaP accumulation seems to be strictly dependent on PHA synthesis, which is catalyzed by the PhaC PHA synthase. Here we have tested t...