title: Microbial-based synthesis of highly elastomeric biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) thermoplastic.
abstract: This study reports the production of P(3HB-co-4HB) [Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)] in possession of high molecular weight and elastomeric properties by Cupriavidus sp. USMAA1020 in single-stage mixed-substrate cultivation system. 1,4-butanediol and 1,6-hexanediol are found to be efficient substrate mixture that has resulted in high copolymer yield, occupying a maximum of 70wt% of the total biomass and producing higher 4HB monomer composition ranging from 31mol% to 41mol%. In substrate mixtures involving 1,6-hexanediol, cleavage of the 6-hydroxyhexanoyl-CoA produces Acetyl-CoA and 4-hydroxybutyryl-CoA. Acetyl-CoA is instrumental in initiating the cell growth in the single-stage fermentation system, preventing 4-hydroxybutyryl-CoA from being utilized via β-oxidation and retained the 4HB monomer at higher ratios. Macroscopic kinetic models of the bioprocesses have revealed that the P(3HB-co-4HB) formation appears to be in the nature of mixed-growth associated with higher formation rate during exponential growth phase; evidenced by higher growth associated constants, α, from 0.0690g/g to 0.4615g/g compared to non-growth associated constants, β, from 0.0092g/g/h to 0.0459g/g/h. The P(3HB-co-31mol% 4HB) produced from the substrate mixture exhibited high weight-average molecular weight, Mwof 927kDa approaching a million Dalton, and possessed elongation at break of 1637% upon cultivation at 0.56wt% C. This is the first report on such properties for the P(3HB-co-4HB) copolymer. The copolymer is highly resistant to polymer deformation after being stretched.
authors.affiliation: Malaysian Institute of Pharmaceuticals and Nutraceuticals, NIBM, 11700 Gelugor, Penang, Malaysia; School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.
authors.forename: Kai-Hee
authors.initials: KH
authors.lastname: Huong
authors.affiliation: Bruker Malaysia Sdn. Bhd, 303 Block A, Mentari Business Park, No 2 Jalan PJS 8/5 Dataran Mentari, 46150 Petaling Jaya, Malaysia.
authors.forename: Chin-Hoe
authors.initials: CH
authors.lastname: Teh
authors.affiliation: Malaysian Institute of Pharmaceuticals and Nutraceuticals, NIBM, 11700 Gelugor, Penang, Malaysia; School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia; Centre for Chemical Biology, Universiti Sains Malaysia, 11900 Bayan Lepas, Penang, Malaysia. Electronic address: amirul@usm.my.
authors.forename: A A
authors.initials: AA
authors.lastname: Amirul
mesh_terms: D002244:Carbon / Q000378:metabolism; D049921:Cupriavidus / Q000378:metabolism*; D020724:Elastomers / Q000737:chemistry / Q000378:metabolism*; D006885:Hydroxybutyrates / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D010969:Plastics / Q000737:chemistry / Q000378:metabolism*; D011091:Polyesters / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D000094122:Polyhydroxybutyrates
chemical_list: D002244:Carbon; D020724:Elastomers; D006885:Hydroxybutyrates; D010969:Plastics; D011091:Polyesters; C068056:poly(3-hydroxybutyrate-co-4-hydroxybutyrate); D000094122:Polyhydroxybutyrates
keywords: Elastomeric; Kinetic modelling; Molecular weight; P(3HB-co-4HB) copolymer; Polyhydroxyalkanoates; Single-stage mixed-substrate cultivation system