Biosynthesis and Properties of Medium-Chain-Length Polyhydroxyalkanoates with Enriched Content of the Dominant Monomer

Abstract

When grown in a nonanoic acid-limited chemostat at a dilution rate of 0.25 h(-1), Pseudomonas putida KT2440 produced poly(3-hydroxynonanoate-co-3-hydroxyheptanoate) containing 68 mol % 3-hydroxynonanoate (C9) and 32 mol % 3-hydroxyheptanoate (C7). Under the same conditions, but in the presence of acrylic acid, a fatty acid β-oxidation inhibitor, the C9 monomer content increased to 88 mol %. Cofeeding glucose (3.9 g L(-1)) and nonanoic acid (2.9 ± 0.1 g L(-1)) in continuous culture with 0.2 g L(-1) of acrylic acid in the feed, further increased the C9 content to 95 mol %. A yield of PHA from nonanoic acid of 0.93 mol mol(-1) was attained. PHA with a 3-hydroxyoctanoate (C8) content of 98 mol % was produced with the same cofeeding methodology from octanoic acid. As the dominant monomer content increased, the melting point of the poly(3-hydroxynonanoate) copolymers increased from 46 to 63 °C and that of the poly(3-hydroxyoctanoate) copolymers from 54 to 62 °C. All copolymer compositions resulted in elongation to break values of about 1300%, but tensile strength at break and Young's modulus both increased with increasing amounts of the dominant monomer.

Simultaneous Enzyme/Whole‐Cell Biotransformation of C18 Ricinoleic Acid into (R)‐3‐Hydroxynonanoic Acid, 9‐Hydroxynonanoic Acid, and 1,9‐Nonanedioic Acid

“…[1] For instance, the engineered whole-cell based biocatalysis permitted the production of a variety of chemicals including medium chain w-hydroxycarboxylic acids, a,w-dicarboxylic acids, and w-aminocarboxylic acids from renewable oils and fatty acids. 9-Hydroxynonanoic acid and 1,9-nonanedioic acid, which are used as monomers for the production of polyesters and polyamides, [3] are currently manufactured via ozonolysis of oleic acid [4,3c] 3-Hydroxynonanoic acid, which can be used as an antimicrobial agent [5] and a building block for the synthesis of polyhydroxyalkanoates [6,7] and rhamnolipids, [8] is difficult to produce by chemical means. 9-Hydroxynonanoic acid and 1,9-nonanedioic acid, which are used as monomers for the production of polyesters and polyamides, [3] are currently manufactured via ozonolysis of oleic acid [4,3c] 3-Hydroxynonanoic acid, which can be used as an antimicrobial agent [5] and a building block for the synthesis of polyhydroxyalkanoates [6,7] and rhamnolipids, [8] is difficult to produce by chemical means.…”

Overproduction of MCL‐PHA with high 3‐hydroxydecanoate Content

“…Mcl‐PHA thermomechanical properties can be greatly improved by increasing the dominant monomer content, since this increases crystallinity (Chung et al, ; Liu et al, ; Ouyang et al, ; Tripathi et al, ). Dominant monomer content can be increased by deletion (Ouyang et al, ) or inhibition (Jiang, Sun, Marchessault, Ramsay, & Ramsay, ) of key enzymes at the initial stages of the β‐oxidation pathway. This also reduces cost of production by diverting more carboxylic acid carbon into polymer since less is lost as acetate.…”

Fed-batch production of MCL-PHA with elevated 3-hydroxynonanoate content

“…In an earlier study (Jiang et al 2012), we showed that increasing HN monomers had no significant effect on the weight average molecular weight but did affect thermal and mechanical properties. The increase in the HN content probably reflects increasing β-oxidation inhibition with the increasing acrylic acid concentration.…”

“…where X 0 (g) is the estimated biomass at the beginning of the feeding; μ (h -1 ) is the desired specific growth rate; and Y X/C is the yield (g g -1 ) of biomass from the mixture of carbon substrates which was 0.66 g g -1 , experimentally determined from continuous fermentation by feeding nonanoic acid, glucose and acrylic acid at a mass ratio of 1.25: 1: 0.05 at a specific growth rate of 0.25 h -1 (Jiang et al 2012). …”