Microscopic examination in vivo and in vitro of natural and cross-linked polyunsaturated mclPHA

Abstract

Pseudomonas aeruginosa 42A2 produces a polyunsaturated polyhydroxyalkanoates (PHA-L) when grown on linseed oil as a substrate. Its high unsaturation content (36.5%) provides highly reactive PHA-L, generating a cross-linked biopolymer after ultraviolet (UV) irradiation. Both PHAs (PHA-L and uvPHA-L) were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, gas chromatography-mass spectrometry and differential scanning calorimetry-thermogravimetric analysis. The structural analysis of the new polymer revealed a dramatic decrease in unsaturated monomer content (8.5%), due to the complete disappearance of the polyunsaturated monomers (C(12:2), C(14:2), and C(14:3)). The cross-linking reaction was also confirmed by atomic force microscopy (AFM) and transmission electron microscopy. AFM showed morphological changes in bacteria cells with and without PHA granules. The microscope techniques provided us with micrographs of the native and cross-linked polymers, showing the formation of a reticular structure as the consequence of the cross-linking reaction.

In vivo and in vitro observations of polyhydroxybutyrate granules formed by Dinoroseobacter sp. JL 1447

“…Furthermore, the enlargement of cell volume is observed in E. coli when PHA granules increase [45]. Similar to our results, AFM of P. aeruginosa shows that PHA granules protrude from the cell surface [31]. Thus, the ranges of variation in cell morphology caused by the PHA granuleforming mechanism may depend on the cultural conditions and the bacterial species.…”

“…Two kinds of PHA surface were reported: (1) a filmlike structure around the PHA granules comprised of short-chain length polymers from Comamonas acidovorans and; (2) a networked surface of PHA granules comprised of medium-chain length polymers from P. oleovorans [27]. In the years, following this, much work was done acquiring the knowledge of the surface morphology of PHA granules through AFM, but thus far no common understanding has been reached [28][29][30][31].…”

Rheological Behavior of High Cell Density Pseudomonas putida LS46 Cultures during Production of Medium Chain Length Polyhydroxyalkanoate (PHA) Polymers

“…This, in turn, increases the shear stress, which then affects the molecules of lower M w [59]. The intermolecular associations may include crosslinking, which is a known phenomenon with mcl-PHA [60][61][62][63].…”

Emerging Technologies in Algal Biotechnology: Toward the Establishment of a Sustainable, Algae-Based Bioeconomy

“…Polyhydroxyalkanoates (PHAs), one of the widely studied biodegradable polyesters with high mechanical strength and melting point, is naturally produced in certain bacteria, including some cyanobacteria (Sudesh et al, 2000). Microbial production of PHAs generally occurs under stressful environmental conditions (Bassas et al, 2008;Balaji et al, 2013). PHA is generally extracted by three subsequent steps of disrupting the cells (by chemical, physical or biological treatment), recovery of PHAs, and purification (Fiorese et al, 2009).…”