Pseudomonas sp. 61-3 accumulates a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer, poly(3-hydroxybutyrate-
co-3-hydroxyalkanoate) [P(3HB-
co-3HA)], consisting of 3HA units of 4–12 carbon atoms.
Pseudomonas sp. 61-3 possesses two types of PHA synthases, PHB synthase (PhbC) and PHA synthases
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Pseudomonas sp. 61-3 accumulates a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer, poly(3-hydroxybutyrate-
co-3-hydroxyalkanoate) [P(3HB-
co-3HA)], consisting of 3HA units of 4–12 carbon atoms.
Pseudomonas sp. 61-3 possesses two types of PHA synthases, PHB synthase (PhbC) and PHA synthases (PhaC1 and PhaC2), encoded by the
phb and
pha loci, respectively. The P(94 mol% 3HB-
co-6 mol% 3HA) copolymer synthesized by the recombinant strain of
Pseudomonas sp. 61-3 (
phbC::
tet) harboring additional copies of
phaC1 gene is known to have desirable physical properties and to be a flexible material with moderate toughness, similar to low-density polyethylene. In this study, we focused on the production of the P(3HB-
co-3HA) copolymer using steamed soybean wastewater, a by-product in brewing
miso, which is a traditional Japanese seasoning. The steamed soybean wastewater was spray-dried to produce a powder (SWP) and used as the sole nitrogen source for the synthesis of P(3HB-
co-3HA) by the
Pseudomonas sp. 61-3 recombinant strain. Hydrolyzed SWP (HSWP) was also used as a carbon and nitrogen source. P(3HB-
co-3HA)s with relatively high 3HB fractions could be synthesized by a recombinant strain of
Pseudomonas sp. 61-3 (
phbC::
tet) harboring additional copies of the
phaC1 gene in the presence of 2% glucose and 10–20 g/L SWP as the sole nitrogen source, producing a PHA concentration of 1.0–1.4 g/L. When HSWP was added to a nitrogen- and carbon-free medium, the recombinant strain could synthesize PHA without glucose as a carbon source. The recombinant strain accumulated 32 wt% P(3HB-
co-3HA) containing 80 mol% 3HB and 20 mol% medium-chain-length 3HA with a PHA concentration of 1.0 g/L when 50 g/L of HSWP was used. The PHA production yield was estimated as 20 mg-PHA/g-HSWP, which equates to approximately 1.0 g-PHA per liter of soybean wastewater.
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