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Joint Event
February 21-22, 2019 | Paris, France
Microbiology & Applied
Microbiology
2
nd
International Conference on
World Congress on
Wound Care, Tissue Repair
and Regenerative Medicine
&
Journal of Trauma and Critical Care | Volume 3
Production of 4-methyl-1-pentanol biofuel from monomers of poly(3-hydroxy-4-methylvalerate)
Paul R Gill
1
and
Silvia Batista
2
1
Ecosystem Intrinsics, Uruguay
2
Molecular Microbiology Unit, Uruguay
S
ustainable alternatives for petroleum-based products
such as plastics and gasoline must be developed promptly.
Herbaspirillum seropedicae
is an endophyte that naturally
produces polyhydroxyalkanoates (PHAs), like many bacteria.
PHAs are widely considered to be bioplastics, and poly-3-
hydroxybutyrate, PHB, which is most commonly produced
by many bacteria is stiff, brittle and has few applications. Co-
polymers like poly-3-hydroxybutyrate-co-3-hydoxyvalerate,
P(3HB-co-3HV), on the other hand, are more flexible, durable
and more like polypropylene. What is not appreciated or
reported in the literature is that monomers of other PHAs, e.g.,
poly(3-hydroxy-4-methylvalerate), PH(4me)V,can be chemically
or biochemically reduced to branched-chain higher alcohols
which are next generation biofuels, for PH(4me)V conversion
is to 4-methyl-1-pentanol. Development of biofuels from PHAs
with higher energy density and lower vapor pressure than
ethanol, e.g., 4-methyl-1-pentanol, significantly expands use
of PHAs as alternatives for petroleum based products and well
beyond use as bioplastics.
Our previous studies showed that
H. seropedicae
accumulates
PHB when grown on glucose in which two acetyl-CoAs are
condensed to form the 3HB monomer substrate. We also
showed that the co-polymer, P(3HB-co-3HV), was produced
when this bacterium was grown on glucose and nonanoic
acid as co-substrate. Beta-oxidation of nonanoic acid results
in formation of propionyl-CoA which condenses with acetyl-
CoA to form the 3HV monomer substrate. We also found that
a PrPC mutant of this bacterium, in which propionate is not
effectively catabolized, produced significantly higher amounts
of P(3HB-co-3HV). For production of a PHA with a six carbon
monomer, we propose to overexpress an ilvIHCD operon in
H.
seropedicae
such that a high level of 2-ketoisovalerate, valine
metabolite, is produced. Condensation of the CoA derivative
of 2-ketoisovalerate (i.e.,isobutyryl-CoA) with acetyl-CoA forms
PHA monomer substrate, 3-hydroxy-4-methylvaleryl-CoA.
The PHA produced is PH(4me)V, a naturally occurring PHA
that should accumulate in
H. seropedicae
. Monomers of this
PHA will then be isolated and reduced to the corresponding
aldehyde and alcohol, i.e., PHA monomer 3-hydroxy-4-methyl
pentanoic acid (3-hydrox-4-methyl valeric acid) to 4-methyl
pentanoic acid then to 4-methyl pentanal and then to 4-methyl
pentanol. Removal of the 3-hydroxy group will make use of part
of a glutamate fermentation pathway used by some Clostridia
that involves conversion of 3-hydroxybutyryl-CoA to butyryl-
CoA (Dawes & Sutherland, 1992). Also, extracts of Clostridium
butyricum can be used to reduce a fatty acyl-CoA to the
corresponding aldehyde and alcohol (Day et al., 1970). A large
number of PHA depolymerases have also been described, e.g.,
in various Clostridia.
The 4-methyl pentanol produced will then be tested as fuel like
ethanol. Our proposed studywill focus on PH(4me)Vproduction
in the lab using standard methods for PHA production,
isolation and characterization. Recombinant
H. seropedicae
overexpressing an ilvIHCD operon from another Herbaspirillum
sp., an Oxalobacteraceae or Burkholderiales will be tested for
PH(4me)V production.
e:
prgillrivers@gmail.comJ Trauma Crit Care, Volume 3
DOI: 10.4066/2591-7358-C1-003