The halophilic archaeon Haloferax mediterranei, has shown promise for the
production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), a desirable
bioplastic, from many low-cost carbon sources. To obtain a full understanding of
PHBHV biosynthesis and to provide novel strategies for polyhydroxyalkanaote (PHA)
production by haloarchaea, the complete genome of H. mediterranei has been
determined, and a genome-wide investigation of the genetics and metabolism of this
haloarchaeon involved in PHBHV biosynthesis was performed in the past few years.
This exploration covers the identification of key genes for PHBHV biosynthesis, the
specific precursor supplying pathways, the PHA granule modulation, and PHBHV
mobilization, as well as its linkage to haloarchaeal-specific acetyl-CoA and propionyl-
CoA assimilation. These advances have not only revealed many haloarchaeal-specific
enzymes and pathways for PHBHV biosynthesis, such as the archaeal-type PHA
synthases, the haloarchaeal-type β-ketothiolases with two distinct subunits, and the
novel 3-hydroxypropionate pathway coupling CO2 fixation into PHBHV, but have also
provided strategies for bioengineering haloarchaea for economical production of
PHBHV or tailor-made higher-value PHA. This chapter will summarize these current
progresses of PHBHV biosynthesis by H. mediterranei, thus providing a perspective
for economical production of industry-scale or higher-value PHAs by haloarchaea in
the near future.
Keywords: Acetoacetyl-CoA reductase, Acetyl-CoA, β-ketothiolase, β-oxidation, Carbon
sources, Copolyester, Economical production, Genes, Genome, Haloferax mediterranei,
Halophilic archaea, PHA biosynthesis, PHA depolymerase, PHA granule, PHA
mobilization, PHA synthase, Polyhydroxyalkanoates (PHA), Poly(3-hydroxybutyrate-co-
3-hydroxyvalerate) (PHBHV), Propionyl-CoA, Regulation, Tailor-made PHA,
Terpolyester.
