Mini-Review: Biosynthesis of Poly(hydroxyalkanoates)

Start a Research on Biopolymer Polyhydroxyalkanoate (PHA): A Review

“…In-depth reviews on these various PHA biosynthesis pathways and the enzymes involved have been provided by Chen [11], Lu et al [4], Madison and Huisman [13], and Khosravi-Darani et al [21]. Figure 3 shows the various routes of scl-PHA synthesis (pathways A to J) and mcl-PHA synthesis (pathways J to M) while Table 1 provides a summary of the enzymes involved.…”

“…A PHA molecule is typically made up of 600 to 35,000 (R)-hydroxy fatty acid monomer units [3]. Each monomer unit harbors a side chain R group which is usually a saturated alkyl group ( Figure 1) but can also take the form of unsaturated alkyl groups, branched alkyl groups, and substituted alkyl groups although these forms are less common [4]. Depending on the total number of carbon atoms within a PHA monomer, PHA can be classified as either short-chain length PHA (scl-PHA; 3 to 5 carbon atoms), medium-chain length PHA (mcl-PHA; 6 to 14 carbon atoms), or long-chain length PHA (lcl-PHA; 15 or more carbon atoms) [3].…”

“…Figure 3 shows the various routes of scl-PHA synthesis (pathways A to J) and mcl-PHA synthesis (pathways J to M) while Table 1 provides a summary of the enzymes involved. Although the biosynthesis of PHA from (R)-hydroxyalkyl-CoA ([R]-3-HA-CoA) precursors were most commonly reported, the diversity of PHA precursors is not restricted to (R)-3-HA-CoA alone [4]. Putative metabolic routes, such as pathways L and M (Figure 3), were recently proposed to expound for the metabolism of cyclohexanol to 6-hydroxyhexanoyl-CoA and 4,5-alkanolactone to 4,5-hydroxyacylCoA (4,5-HA-CoA) [11].…”

“…Additionally, bacteria that harbor PHA showed enhanced stress tolerance against transient environmental assaults such as ultraviolet (UV) irradiation, heat and osmotic shock [12]. PHA biosynthetic pathways are intricately linked with the bacterium's central metabolic pathways including glycolysis, Krebs Cycle, β-oxidation, de novo fatty acids synthesis, amino acid catabolism, Calvin Cycle, and serine pathway [4,[13][14][15][16][17]. Many common intermediates are also shared between PHA and these metabolic pathways, most notably being acetyl-CoA.…”

A platform pathway for production of 3-hydroxyacids provides a biosynthetic route to 3-hydroxy-γ-butyrolactone

“…3-Hydroxyacids are also naturally produced as components of polyhydroxyalkanoate (PHA) biopolymers 24 and can in turn be used to synthesize PHAs with novel properties 25,26 . Although many substituent monomers have been incorporated into PHAs through modulation of substrates provided in the culture medium 26,27 , the number of monomers produced directly from simple carbon sources is far smaller. Indeed, only 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) have been successfully produced at the gram per litre scale using enzymes of the PHA biosynthetic pathway [28][29][30] .…”