Biosynthesis of Polyhydroxyalkanoate from Steamed Soybean Wastewater by a Recombinant Strain of Pseudomonas sp. 61-3

Abstract

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.

Advances in Polyhydroxyalkanoate (PHA) Production

“…Most of all, the authors underlined the independence of this substrate from food and feed applications, making the process ethically clear. In addition, it turned out that a PHBHV copolyester with abbot 11% 3HV in PHA is produced by C. necator when supplied with this substrate [ 15 ], which is similar to the findings for other new production strains in this special issue [ 17 , 18 , 20 ].…”

“…Using hydrolyzed spray-dried soybean wastewater as the sole carbon source, the highest achieved concentration of this PHA blend amounted to 1 g/L, which corresponds to a PHA fraction of 35% of the cell dry mass. In this case, the blend contained about 80% 3HB and 20% longer building blocks, and displayed a flexible material with considerable toughness comparable to the characteristics displayed by poly(ethylene) (PE) [ 20 ].…”

“…First, six articles deal with the assessment of inexpensive [ 16 , 17 , 18 , 19 , 20 ] or exotic [ 21 ] feedstocks to be used as carbon sources for PHA production. Importantly, these feedstocks constitute carbonaceous (agro)industrial waste streams, such as waste glycerol from biofuel production [ 16 , 17 ], lignocellulose waste from the food industry [ 18 , 20 ] and forestry [ 19 ], and even petrochemical plastic waste [ 21 ]. These works aim to find alternatives to commonly used feedstocks of value for human nutrition, in order to avoid the current “plate vs. plastic” dispute.…”

A Review on Established and Emerging Fermentation Schemes for Microbial Production of Polyhydroxyalkanoate (PHA) Biopolyesters

“…Mcl-PHA, in most cases, are heteropolyesters of different randomly distributed hydroxyalkanotes with at least six carbon atoms. They are typically synthetized by Gram-negative bacteria from the genus Pseudomonas and, in contrast to scl-PHA, display low crystallinity and low glass transition temperature; macroscopically, they appear as highly elastic "bio-latexes" [39]. The generation of mcl-PHA homopolyesters such as poly(3-hydroxyhexanoate) (PHHx) or poly(3-hydroxyoctanoate (PHO) is mainly described by genetically engineered production strains [40].…”

Advances in Polyhydroxyalkanoate (PHA) Production

“…In principle, these contributions are dedicated to four major impact directions of PHA research: First, six articles deal with the assessment of inexpensive [16][17][18][19][20] or exotic [21] feedstocks to be used as carbon sources for PHA production. Importantly, these feedstocks constitute carbonaceous (agro)industrial waste streams, such as waste glycerol from biofuel production [16,17], lignocellulose waste from the food industry [18,20] and forestry [19], and even petrochemical plastic waste [21].…”