Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Production by Rhodospirillum rubrum Using a Two-Step Culture Strategy

Abstract

Polyhydroxyalkanoates (PHAs) are microbially synthesized biopolyesters which have attracted great attentions as a new biological material, potential alternative to traditional fossil fuel-based plastic due to their biodegradability and biocompatibility. Poly-3-hydroxybutyrate (PHB) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) are the most common members of PHAs. In this study, the nonsulfur and facultatively phototrophic bacterium Rhodospirillum rubrum was cultivated to accumulate PHA by a two-step culture strategy. Gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance spectroscopy (NMR) analyses showed that PHAs synthesized from fructose was PHBV, in which the 3HV content was 46.5 mol%, which means the better mechanical property. The molecular weight, distribution, and thermal features were characterized by gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and thermo gravimetric analysis (TGA), respectively. The low PDI of 1.08 revealed the narrow and evenly molar mass distribution which shows the stable features. The high melting temperature and their other physical properties implied their potential applications. The traditional process of producing PHBV involves related carbon sources such as valeric acid. However, our study clearly described a new medium formula with fructose and a complete fermentation method to produce PHBV with a high 3HV faction and low molecular distribution.

Low Crystallinity of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Bioproduction by Hot Spring Cyanobacterium Cyanosarcina sp. AARL T020

“…AARL T020, two-stage cultivation was shown to facilitate maximal biomass yield. This strategy demonstrates the noteworthy capabilities of PHBV production, not only in cyanobacteria but also in bacteria, as previously reported [ 57 ]. Furthermore, this strategy could be implemented in the production of several secondary metabolized substances, such as astaxanthin in Haematococcus pluvialis JNU35, extracellular polymeric substances (EPS) in Arthrospira sp., docosahexaenoic acid in Crypthecodinium cohnii , and lipid production in Dunaliella tertiolecta [ 58 , 59 , 60 , 61 ].…”

Effect of 3-Hydroxyvalerate Content on Thermal, Mechanical, and Rheological Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers Produced from Fermented Dairy Manure

“…An Increase in 3HV content results in an increase in the amorphous phase and thus leads to a reduction in X c and T c [ 48 ]. A lower T c indicates that the complete crystallization takes a longer time [ 49 ]. PHBV-15 has the lowest 3HV content (0.16), high X c (29%), and low T c of 62 °C.…”

“…Higher PDI indicates a larger size distribution of polymer chains. Shorter chains need less time for crystallization compared to longer chains which results in reduction of T c [ 49 ]. A T c value ranging from 41 to 82 °C for CHCl 3 extracted PHBV with 3HV contents of (20–60%) have been reported [ 50 ].…”

“…For PHB thermal degradation occurs just above its T m which limits its processability [ 7 ]. The presence of 3HV in PHBV lowers its T m relative to T d and thus improves its processing window for molding and extrusion [ 21 , 31 , 49 , 54 ]. The thermal degradation of PHBV occurs in a single step due to a nonradical random chain scission process involving a six-membered ring transition state [ 24 , 31 , 52 , 55 ].…”

Improving biological production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) co-polymer: a critical review

“…Nevertheless, it has been demonstrated that the PNSB Rhodospirillum Rubum synthetizes PHBV from sugars and wastes without the need of precursors supply (Smith et al 2008;Liu et al 2019). In particular, in a study from Liu et al (2019), a 46.5% 3HV fraction was observed, which was the highest obtained in all the reviewed studies from unrelated carbon sources.…”