3 research outputs found
The microbial production of polyhydroxyalkanoates from waste polystyrene fragments attained using oxidative degradation
© 2018 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence.
The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/polym10090957Excessive levels of plastic waste in our oceans and landfills indicate that there is an
abundance of potential carbon sources with huge economic value being neglected. These waste
plastics, through biological fermentation, could offer alternatives to traditional petrol-based plastics.
Polyhydroxyalkanoates (PHAs) are a group of plastics produced by some strains of bacteria that
could be part of a new generation of polyester materials that are biodegradable, biocompatible,
and, most importantly, non-toxic if discarded. This study introduces the use of prodegraded high
impact and general polystyrene (PS0). Polystyrene is commonly used in disposable cutlery, CD cases,
trays, and packaging. Despite these applications, some forms of polystyrene PS remain financially
and environmentally expensive to send to landfills. The prodegraded PS0 waste plastics used were
broken down at varied high temperatures while exposed to ozone. These variables produced PS
flakes (PS1–3) and a powder (PS4) with individual acid numbers. Consequently, after fermentation,
different PHAs and amounts of biomass were produced. The bacterial strain, Cupriavidus necator
H16, was selected for this study due to its well-documented genetic profile, stability, robustness,
and ability to produce PHAs at relatively low temperatures. The accumulation of PHAs varied from
39% for prodegraded PS0 in nitrogen rich media to 48% (w/w) of dry biomass with the treated PS.
The polymers extracted from biomass were analyzed using nuclear magnetic resonance (NMR) and
electrospray ionization tandem mass spectrometry (ESI-MS/MS) to assess their molecular structure
and properties. In conclusion, the PS0–3 specimens were shown to be the most promising carbon
sources for PHA biosynthesis; with 3-hydroxybutyrate and up to 12 mol % of 3-hydroxyvalerate and
3-hydroxyhexanoate co-monomeric units generated
Mass spectrometry reveals molecular structure of polyhydroxyalkanoates attained by bioconversion of oxidized polypropylene waste fragments
This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a microbiological shake flask experiment utilizing oxidized polypropylene (PP) waste as an additional carbon source. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust, and one of the best known producers of PHA. Making use of PHA oligomers, formed by controlled moderate-temperature degradation induced by carboxylate moieties, by examination of both the parent and fragmentation ions, the ESI-MS/MS analysis revealed the 3-hydroxybutyrate and randomly distributed 3-hydroxyvalerate as well as 3-hydroxyhexanoate repeat units. Thus, the bioconversion of PP solid waste to a value-added product such as PHA tert-polymer was demonstrated.This research was funded by the Research Investment Fund, University of Wolverhampton, Faculty of Science and Engineering, UK. This work was also partially supported the European Regional Development Fund Project EnTRESS No 01R16P00718 and the PELARGODONT Project UM0-2016/22/Z/STS/00692 financed under the M-ERA.NET 2 Program of Horizon 2020.Published onlin
Polyhydroxyalkanoate biosynthesis by Hydrogenophaga pseudoflava DSM1034 from structurally unrelated carbon sources
none8In the present paper we report the exclusive microbial preparation of polyhydroxyalkanoates (PHA) containing 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV) and 4-hydroxybutyrate (4HB) as
comonomers through the use of unexpensive carbon sources such as whey from dairy industry. Polymers
were produced by growing H. pseudoflava DSM 1034 in minimal medium supplemented with sucrose,
lactose or whey without any co-substrate added. The chemical and physical properties of the polymers
were fully characterized by GPC, DSC, TGA analyses and the composition by GC and 1H NMR
examinations to especially confirm the content of different monomeric units. The presence of 4HB units
into PHA samples is particularly aimed in thermoplastic applications where greater flexibility is required
and conventional rigid PHAs tend to fail. Usually the insertion of 4HB into chain backbone consisting of
3-hydroxyalkanoates requires expensive carbon sources mostly of petrochemical origin. According to
our study the production of P(3HB-co-3HV-co-4HB) terpolymer can be obtained directly by the use of
lactose or waste raw materials such as cheese whey as carbon sources. Although the amount of 4HB in the
produced terpolymers was usually low and not exceeding 10% of the total molar composition, a PHA
containing 18.4% of 4HB units was produced in 1 step fermentation process from this structurally
unrelated carbon sources. The crystallinity of the terpolymer is basically to be markedly affected with respect to that of conventional PHAs, thus obtaining a comparatively less rigid material and easier to be processed.noneSilvana Povolo; Maria Giovanna Romanelli; Marina Basaglia; Vassilka Ivanova Ilieva; Andrea Corti; Andrea Morelli; Emo Chiellini; Sergio CasellaSilvana, Povolo; Romanelli, MARIA GIOVANNA; Basaglia, Marina; Vassilka Ivanova, Ilieva; Andrea, Corti; Andrea, Morelli; Emo, Chiellini; Casella, Sergi