Biosynthesis and Properties of a P(3HB-co-3HV-co-4HV) Produced by Cupriavidus necator B-10646

Abstract

Synthesis of P(3HB-co-3HV-co-4HV) copolymers by the wild-type strain Cupriavidus necator B-10646 on fructose or sodium butyrate as the main C-substrate with the addition of γ-valerolactone as a precursor of 3HV and 4HV monomers was studied. Bacterial cells were cultivated in the modes that enabled production of a series of copolymers with molar fractions of 3HV (from 7.3 to 23.4 mol.%) and 4HV (from 1.9 to 4.7 mol.%) with bacterial biomass concentration (8.2 ± 0.2 g/L) and PHA content (80 ± 2%). Using HPLC, DTA,DSC, X-Ray, SEM, and AFM, the physicochemical properties of copolymers and films prepared from them have been investigated as dependent on proportions of monomers. Copolymers are characterized by a reduced degree of crystallinity (Cx 38–49%) molecular weight characteristics Mn (45–87 kDa), and Mw (201–248 kDa) compared with P(3HB). The properties of the films surface of various composition including the porosity and surface roughness were studied. Most of the samples showed a decrease in the average pore area and an increase in their number with a total increase in 3HV and 4HV monomers. The results allow scaling up the productive synthesis of P(3HB-co-3HV-co-4HV) copolymers using Cupriavidus necator B-10646.

Biodegradable Polyhydroxyalkanoates with a Different Set of Valerate Monomers: Chemical Structure and Physicochemical Properties

“…The polydispersity value was also similar (4.9 and 3.0). This was comparable with the data of [ 50 ], in which a series of P(3HB- co -3HV- co -4HV) samples with different ratios of 4HV, 3HV, and 3HB monomers had similar weight average molecular weights (201–248 kDa) with varying polydispersity from 2.9 to 4.9.…”

“…Earlier, when studying a series of these copolymers (six samples), amorphization was also shown when in addition to 3HB monomers, 4HV monomers were included in the composition of PHA, even in small amounts (from 1.9 to 4.7 mol.%). C x values were below 50% and varied in the range of 38–49% [ 50 ].…”

“…The properties of the polymers changed not only by the set of monomers but also by their ratio (Table 1). * data from the first heating, ** the sample was synthesized earlier [50], *** the sample was synthesized earlier [51].…”

“… * data from the first heating, ** the sample was synthesized earlier [ 50 ], *** the sample was synthesized earlier [ 51 ]. …”

Natural Polyhydroxyalkanoates—An Overview of Bacterial Production Methods

“…C. necator is able to accumulate 66% PHA with up to 13% PHV when using butyrate as its sole carbon source [136]. The cultivation of C. necator on butyrate supplied by γ-valerolactone resulted in 78% PHA accumulation with 31% PHV [137].…”