Abstract
Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs’ biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels’ production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.
Highlights
Polyhydroxyalkanoates (PHAs) are a group of bacterial polyesters produced by a variety of prokaryotic microorganisms under unbalanced nutrition conditions as carbon and energy storage materials [1]
Hydrocarbons can be metabolised by many microorganisms. Both gaseous n-alkanes and 1-alkenes (C1–C6) and long-chain paraffinic or olefinic hydrocarbons up to 44 carbons can be used by these microorganisms [87]. Not all of these hydrocarbon-utilising microorganisms can accumulate PHAs. de Smet et al [88] first identified that P. oleovorans and other fluorescent Pseudomonads can be grown on octane and accumulate mcl-PHAs in 1983
We propose an integration of PHA production within a biorefinery, which may offset the cost of bioethanol by co-production of value-added PHAs
Summary
Polyhydroxyalkanoates (PHAs) are a group of bacterial polyesters produced by a variety of prokaryotic microorganisms under unbalanced nutrition conditions as carbon and energy storage materials [1]. Production of these carbon sources competes with food supply production. Asusmummmarayryofofththe esusubbstsrtaratetsesfoforrPPHHAA ssyynntthheessiiss aanndd ttyyppiiccaall mmiiccrroooorrggaanniissmmss tthhaatt ccaann uussee tthhee ssuubbssttrraatteess iiss ggiivveenn iinn FFiigguurree 22. AA ssuummmmaarryy ooff tthhee ssuubbssttrraatteess aanndd tthhee mmiiccrroooorrggaanniissmmss tthhaatt ccaann ssyynntthheessiizzee PPHHAAss. PP33HHHHxx == ppoollyy((33--hhyyddrrooxxyyllhheexxaannooaattee));; PP33HHOO == ppoollyy((33--hhyyddrrooxxyyooccttooaattee));; PP33HHDD == ppoollyy((33--hhyyddrrooxxyyddooddeeccaannooaattee));; PP33HHBB == ppoollyy((33--hhyyddrrooxxyybbuuttyyrraattee));; PP33HHVV == ppoollyy((33--hhyyddrrooxxyyvvaalleerraattee))..AA““--ccoo--““iiss uusseedd ttoo iinnddiiccaattee tthhee ccooppoollyymmeerr. OSnimenptsleosfuogilasrfrsoumbsptrlaatnetss aarnedmfaatisnflryomdearinviemdaflsro; ampcoaterbnotihayl dsoruatrecse; otrfiafecyrmlgelynctearbolelshayredrthoceamrbaoinnscoismwpaosnteenptlsaostfiocsil.sInfrothme pfolallnotws ainngd, ftahtes ufrsoemofanthimesaelsc;aarbpoontesnotuiarlcesos uarncde their transformation processes are reviewed, placing an emphasis on the sustainability in order to provide the best vantage point to identify sustainable carbon sources for PHA production. The extent of the availability of molasses is insufficient to satisfy the future increasing demand of PHA production
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